COSEWIC Assessment and Status Report on the Transverse Lady Beetle (Coccinella transversoguttata) in Canada 2016

Transverse Lady Beetle on a leaf
Photo: Transverse Lady Beetle © Steve Marshall, 2016

Special concern
2016


Document information

COSEWIC
Committee on the Status
of Endangered Wildlife
in Canada

COSEWIC logo

COSEPAC
Comité sur la situation
des espèces en péril
au Canada

COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:

COSEWIC. 2016. COSEWIC assessment and status report on the Transverse Lady Beetle (Coccinella transversoguttata) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 57 pp. (Species at Risk Public Registry website).

Production note:

COSEWIC would like to acknowledge Paul Grant for writing the status report on the Transverse Lady Beetle (Coccinella transversoguttata) in Canada, prepared under contract with Environment and Climate Change Canada. This status report and was overseen and edited by Jennifer Heron, Co-chair of the COSEWIC Arthropods Specialist Subcommittee.

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment and Climate Change Canada
Ottawa, ON
K1A 0H3

Tel.: 819-938-4125
Fax: 819-938-3984
E-mail: COSEWIC E-mail
Website: COSEWIC

Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur la Coccinelle à bandes transverses (Coccinella transversoguttata) au Canada.

Cover illustration/photo:

Transverse Lady Beetle -- Photo by Steve Marshall.


COSEWIC assessment summary

Assessment summary – November 2016

Common name
Transverse Lady Beetle
Scientific name
(Coccinella transversoguttata)
Status
Special Concern
Reason for designation
This species was once common and broadly distributed throughout most of Canada. Declines started in the 1970s and the species is now absent in southern Ontario and the Maritimes. In some parts of its western and northern range, the species is still commonly recorded. The spread of non-native lady beetles is considered one of the possible threats to this species through competition, intraguild predation, or introduction of pathogens. Non-native lady beetles are less commonly found in places where this species remains.
Occurrence
Yukon, Northwest Territories, Nunavut, British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Prince Edward Island, Nova Scotia, Newfoundland and Labrador
Status history
Designated Special Concern in November 2016.

COSEWIC executive summary

Transverse Lady Beetle
(Coccinella transversoguttata)

Wildlife species description and significance

Transverse Lady Beetles are small, round beetles (5.0 to 7.8 mm) that are native to North America. Adults have orange to red wing covers with black markings, consisting of a black band and four elongate spots, which distinguish them from other species. This charismatic species was once one of the more common and widespread lady beetles in North America, playing an important role as a biological control agent of aphids and other insect pests.

Distribution

The Transverse Lady Beetle is a wide-ranging species occurring from coast to coast across Canada and the United States. The Canadian range of the Transverse Lady Beetle stretches from St. John’s, Newfoundland and Labrador, west to Vancouver Island. The northernmost extent of its range includes Yukon, the Northwest Territories and likely Nunavut.

Habitat

Transverse Lady Beetles are habitat generalists, primarily feeding on aphids and occurring across a wide range of habitats. This lady beetle inhabits agricultural areas, suburban gardens, parks, coniferous forests, deciduous forests, prairie grasslands, meadows, riparian areas and other natural areas. This broad habitat range reflects their ability to exploit seasonal changes in prey availability across different vegetation types.

Biology

Transverse Lady Beetles have four life stages: egg, larva, pupa and adult, and can have two generations per year. Adults of the spring generation can undergo aestivation to avoid high summer temperatures, and lay eggs in early autumn. Adults of the autumn generation congregate to overwinter and undergo diapause; becoming active and reproducing when temperatures warm in the early spring. This species occupies a wide ecological niche across a wide variety of habitats and temperature regimes in Canada. In general lady beetles are very mobile, display low site fidelity, and readily engage in short (few hundred metres) and long (18 – 120 km) distance dispersal. This species does not migrate. Both adult and larval stages are predatory and primarily prey on aphids. In turn, this species is also subject to predation by other invertebrates, vertebrates, and is susceptible to parasitoids and pathogens.

Population size and trends

The historically broad geographic range and abundance of the Transverse Lady Beetle stands in stark contrast to its current distribution. Prior to 1986, this species was widely distributed and abundant across North America and was one of the most common lady beetles collected. Currently, in many parts of its range this species is either absent or below detection thresholds where it was formerly common. In other regions it persists in low numbers. In Yukon, the Northwest Territories and British Columbia, however, this species seems to be abundant and common. These regions also have a smaller proportion of non-native lady beetle species, which are considered one of the potential threats to this species and other native lady beetles.

Threats and limiting factors

The specific range-wide causes of decline in the Transverse Lady Beetle are currently unknown. Possible threats to this species may include negative interactions with recently arrived non-native species, such as the Seven-spotted Lady Beetle and Multicolored Asian Lady Beetle through competition, intraguild predation or indirect effects through introduction of pathogens. Other possible localized and cumulative threats include land use changes, such as direct and indirect effects of agricultural pesticide/chemical use to control their prey species, habitat loss through urban expansion, conversion of farmland to forest, and other human disturbances.

Protection, status, and ranks

There are no laws in Canada that protect the Transverse Lady Beetle. This species has not yet been ranked globally or nationally. The Conservation Data Centres across Canada have assigned conservation status ranks as follows: ON: S1, YT: S4; NT: S4S5; BC: S5; AB, SK, MB: S4S5; ON: S1; QC: S4; NB, NS, PE: SH; NF: SU; NF (Labrador only): S5.


Technical summary

Scientific name:
(Coccinella transversoguttata)
English name:
Transverse Lady Beetle
French name:
Coccinelle à bandes transverses
Range of occurrence in Canada:
Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Northwest Territories, Ontario, Prince Edward Island, Quebec, Saskatchewan, Yukon, Nunavut.

Demographic information

Demographic information of the species
Summary itemsInformation
Generation timeTwo generations per year.
Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?Inferred.

There are inferred continuing declines based on past declines. Over the last ten years this species has remained undetected in areas where it was formerly common (SK, ON, NB, NS) or detected in low numbers (QC, AB). In other parts of its range (BC, YT, NT and likely NU) it remains common.
Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations]Unknown.
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations]

Unknown.

Historical declines. Over the lastt 10 years it has remained undetected in areas where it was formerly common (SK, ON, NB, NS) or detected in low numbers (QC, AB). Currently, it is common in BC, YT, NT and likely NU.

[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations].Unknown.
[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future.Unknown.
Are the causes of the decline a) clearly reversible and b) understood and c) ceased?a. Not clearly reversible.
b. Not clearly understood.
c. Unknown.
Are there extreme fluctuations in number of mature individuals?No.

Extent and occupancy information

Extent and occupancy information of the species
Summary itemsinformation
Estimated extent of occurrence (EOO)

10.6 million km2 (all records 1889 – 2015).

EOO > 6.9 million km2 (2006 – 2015)

Trends in this species’ geographic distribution reflect issues with survey coverage and detection rather than expansion or contraction of its range.

Index of area of occupancy (IAO)
(Always report 2x2 grid value).

Inferred IAO is > 2,000 km2.

Trends in this species’ geographic distribution reflect issues with survey coverage and detection rather than expansion or contraction of its range.

Is the population “severely fragmented”

No.

This species is a mobile habitat generalist that is not restricted to specific habitat patches or separated from other habitat patches by a distance greater than the species can disperse.

Number of locations (use plausible range to reflect uncertainty if appropriate)
(Note: See Definitions and abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)

Not applicable.

It is not possible to calculate the number of locations for this species. This species has a broad geographic range, low site fidelity, and threats that are not entirely clear.

Is there an [observed, inferred, or projected] decline in extent of occurrence?

No. Inferred.

Surveys have not been systematic or comprehensive over the species’ range or through time; therefore trends in this species EOO reflect issues with survey coverage and detection rather than expansion or contraction of its range. This species has undergone historical declines (> 10 years before this assessment) although it remains undetected in areas where it was formerly common (SK, ON, NB, NS) or detected in low numbers (QC, AB). In other parts of its range (BC, YT, NT and likely NU) it remains common. It is plausible that the EOO for this species has not changed significantly, even though it has declined in abundance in some regions.

Is there an [observed, inferred, or projected] decline in index of area of occupancy?

Unknown.

Surveys have not been systematic or comprehensive over the species’ range or through time; therefore trends in this species EOO reflect issues with survey coverage and detection rather than expansion or contraction of its range. This species has undergone historical declines (> 10 years before this assessment) although it remains undetected in areas where it was formerly common (SK, ON, NB, NS) or detected in low numbers (QC, AB). In other parts of its range (BC, YT, NT and likely NU) it remains common. It is plausible that the IAO for this species has not changed significantly, even though it has declined in abundance in some regions.

Is there an [observed, inferred, or projected] decline in number of subpopulations?

Yes. Observed and inferred.

Over the last ten years this species has remained undetected in areas where it was formerly common.

Is there an [observed, inferred, or projected] decline in number of “locations”
(Note: See Definitions and abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)

Not applicable.

It is not possible to calculate the number of locations for this species.

Is there an [observed, inferred, or projected] decline in [area, extent and/or quality] of habitat?

Yes.

Inferred continuing decline in quality of habitat.

Are there extreme fluctuations in number of subpopulationsNo.
Are there extreme fluctuations in number of “locations”?
(Note: See Definitions and abbreviations on COSEWIC website and IUCN (Feb 2014) for more information on this term.)
No.
Are there extreme fluctuations in extent of occurrence?No.
Are there extreme fluctuations in index of area of occupancy?No.

Number of mature individuals (in each subpopulation)

Number of mature individuals of the species
Subpopulations (give plausible ranges)N Mature Individuals.
-Unknown.
TotalUnknown.

Quantitative analysis

Quantitative analysis of the species
Summary itemsInformation
Probability of extinction in the wild is at least [20% within 20 years or 5 generations, or 10% within 100 years].Unknown.

Threats (actual or imminent, to populations or habitats, from highest impact to least)

Was a threats calculator was completed for this species? Yes, overall threat impact High-Medium.

8.1 Introduced species, Parasites/ Pathogens (High – Medium impact);

9.3 Pesticide Use (Low impact);

7.3 Other ecosystem modifications (Low impact).

Rescue effect (immigration from outside Canada)

Status of outside population(s)?

The range of this species extends across the United States, where subpopulations have also declined. The source-sink dynamics of this species are unknown, yet this species has the potential to disperse long distances.

Rescue effect of the species
Summary itemsInformation
Is immigration known or possible?Yes.
Would immigrants be adapted to survive in Canada?Yes.
Is there sufficient habitat for immigrants in Canada?Likely.
Are conditions deteriorating in Canada?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Likely, in some parts of the species’ range.
Are conditions for the source population deteriorating?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Yes, in some parts of the species’ range.
Is the Canadian population considered to be a sink?
See Table 3 (Guidelines for modifying status assessment based on rescue effect).
Unknown.
Is rescue from outside populations likely?Unlikely. Populations have declined throughout its range in the United States.

Data-sensitive species

Data-sensitive information of the species
Summary itemsInformation
Is this a data sensitive species?No.

Status history

Status history
Summary itemsInformation
COSEWIC:Designated Special Concern in November 2016.

Status and reasons for designation:

Status and reasons for designation
Summary itemsInformation
Status:Special Concern
Alpha-numeric code:Not applicable
Reasons for designation:This species was once common and broadly distributed throughout most of Canada. Declines started in the 1970s and the species is now absent in southern Ontario and the Maritimes. In some parts of its western and northern range, the species is still commonly recorded. The spread of non-native lady beetles is considered one of the possible threats to this species through competition, intraguild predation, or introduction of pathogens. Non-native lady beetles are less commonly found in places where this species remains.

Applicability of criteria:

Applicability of criteria
Summary itemsInformation
Criterion A
(Decline in total number of mature individuals):
Not applicable. Insufficient information on population trends.
Criterion B
(Small distribution range and decline or fluctuation):
Not applicable. Very wide distribution and above EOO threshold. This species doesn’t meet criteria for locations; it is not severely fragmented and does not have extreme fluctuations.
Criterion C
(Small and declining number of mature individuals):
Not applicable. Insufficient data on number of mature individuals.
Criterion D
(Very small or restricted population):
Not applicable. Insufficient data on number of mature individuals. Canadian population is not restricted in IAO, doesn’t meet criteria for locations, and is not prone to effects of human activities or stochastic events within a very short time period across its range.
Criterion E
(Quantitative analysis):
Not applicable. Insufficient data to make Canadian population projections showing the probability of extinction or extirpation in the wild.

Preface

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2016)

Wildlife species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.
Extinct (X)
A wildlife species that no longer exists.
Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered (E)
A wildlife species facing imminent extirpation or extinction.
Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.
Special concern (SC)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.
Not at risk (NAR)
(Note: Formerly described as “Not In Any Category”, or “No Designation Required.”)
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.
Data deficient (DD)
(Note: Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.


Wildlife species description and significance

Name and classification

Class: Insecta – insects
Subclass: Pterygota – winged insects
Order: Coleoptera – beetles
Family: Coccinellidae – lady beetles
Genus: Coccinella
Species: Coccinella transversoguttata Falderman, 1835
Subspecies: Coccinella transversoguttata richardsoni Brown, 1962
Scientific name: Coccinella transversoguttata richardsoni
English Common Names: Transverse Lady Beetle
French Common Name: Coccinelle à bandes transverses

The family Coccinellidae contains approximately 6,000 species worldwide in about 360 genera (Vandenberg 2002; Giorgi and Vandenberg 2009). In Canada there are approximately 60 genera containing 161 species, including nine non-native species that are now well established throughout the country (Hodek et al. 2012; Bousquet et al. 2013). The taxonomy, identification and geographic distribution of lady beetles in Canada are relatively well known (Dobzhansky 1935; Watson 1956; Brown 1962; Brown and de Ruette 1962; Belicek 1976; Watson 1976; Larochelle 1979; Gordon 1985; Vandenberg 2002; Majka and McCorquodale 2006; Acorn 2007; Marriott et al. 2009; Majka and McCorquodale 2010; Hodek et al. 2012; Bousquet et al. 2013).

(Coccinella transversoguttata) (Transverse Lady Beetle) is widely distributed in the Holarctic region and is represented by four subspecies in the New World and one subspecies from the Old World (Kovář 2005). All C. transversoguttata subspecies are distinct morphologically and geographically (Brown 1962; Gordon 1985; Kovář 2005). Subspecies C. t. transversoguttata occurs in China, Kazakhstan, Kyrgyzstan, Mongolia, Nepal, and Russia (Kovář 2005). Two subspecies C. t. nugatoria and C. t. sonorica occur in Mexico and C. t. ephippiata occurs in Greenland (Kovář 2005).

Only the subspecies C. t. richardsoni occurs north of Mexico. It is widely distributed in Canada and the United States (Kovář 2005). Because it is the only subspecies that occurs in Canada, this report will assess the full species (Coccinella transversoguttata).

Morphological description

Lady Beetles are holometabolous insects, meaning they have four developmental life stages (egg, larva, pupa and adult). Each stage is morphologically different from the next.

Adults:

Colour pattern is sufficient to distinguish adult Transverse Lady Beetles from other lady beetles (Gordon 1985). In comparison to other lady beetles, the Transverse Lady Beetle is considered relatively large. Adults are round, slightly oval beetles measuring 5.0 to 7.8 mm in length (Figure 1). Their elytra (wing covers) are orange to red with black markings. The markings include a black band behind the pronotum stretching across both elytra and two elongated black markings posteriorly on each elytra. The pronotum is black at the anterior margin with white markings on either side. The head is black with two well separated pale spots. Adults do not show exaggerated sexual dimorphism (Stellwag and Losey 2014).

Figure 1. Transverse Lady Beetle (Coccinella transversoguttata richardsoni). Photo by Steve Marshall.
Photo of the Transverse Lady Beetle (dorsal view). (see long description below)
Long description for Figure 1

Photo of the Transverse Lady Beetle (dorsal view). The elytra of this slightly oval beetle are orange to red with black markings. The markings include a black band behind the pronotum stretching across both elytra and two elongated black markings posteriorly on each elytra. The pronotum is black at the anterior margin with white markings on either side. The head is black with two well separated pale spots.

Eggs:

No detailed description for this species exists. Other Coccinella species have yellow- to orange-coloured elongate eggs, approximately 1 mm in length that are laid upright in tightly packed clusters (Hodek et al. 2012).

Larvae:

No detailed description for this species exists. The larval form develops through four instars and the final instar is likely elongate and black with orange spots dorsolaterally. Similar to other closely related Coccinella, the abdomen likely has nine segments and has mound-like projections bearing seta, or hair-like structures (Gordon and Vanderberg 1995).

Pupae:

No description for this species exists. However, the pupae are likely yellow to orange with black markings, as in similar species (Hodek et al. 2012).

Population spatial structure and variability

In Canada, the spatial structure and variability of Transverse Lady Beetle subpopulations have not been studied. Similarly, limited genetic studies have occurred on this species or its genetic structure.

Allozyme variation was investigated in non-native (n = 8) and native (n = 6) lady beetles in North America from Iowa, New York, and Arkansas (Krafsur et al. 2005). This study determined allele diversities and heterozygosities were similar in non-native and native lady beetles and therefore no obvious relationship existed between successful colonization of new habitats and genetic diversity (Krafsur et al. 2005). This study also determined that there were high rates of gene flow within in all lady beetle subpopulations (Krafsur et al. 2005). In addition, all lady beetles showed a remarkable degree of dispersion with little detectable subpopulation subdivision (Krafsur et al. 2005).

Designatable units

The Transverse Lady Beetle has one designatable unit within Canada. The Transverse Lady Beetle occurs across multiple ecozones and there are likely high rates of gene flow and little detectable subpopulation subdivision (Krafsur et al. 2005).

Special significance

The Transverse Lady Beetle was previously one of the more common lady beetle species in Canada. As a predator of a large variety of aphid species in addition to other pest herbivores, it also had an important economic role as a biological control agent in gardens and agricultural crops (Wheeler and Hoebeke 1995; Hesler et al. 2012). The observed decline of this charismatic species has led to public interest in their conservation and their role in ecosystem function (Evans 2004; Harmon et al. 2007; Losey et al. 2007; Gardiner et al. 2011; Gardiner et al. 2012; Losey et al. 2012; Bahlai et al. 2013; Turnipseed et al. 2014; Ugine and Losey 2014).

Initiatives such as the Lost Lady Bug Project, which enable citizen scientists to document the distributions of native species, such as the Transverse Lady Beetle, across North America, demonstrate significant public interest and shifting trends in lady beetle composition across landscapes.

There is no available Aboriginal Traditional Knowledge specifically for the Transverse Lady Beetle.


Distribution

Global range

The Transverse Lady Beetle is a wide-ranging species occurring across Canada and the United States, from Newfoundland to Virginia, and west to Alaska and California (Brown 1962; Gordon 1985) (Figure 2). Approximately 65% of its historical global range is within Canada.

Figure 2. The geographic range of the Transverse Lady Beetle (Coccinella transversoguttata). This range map is based on a historical range map by Gordon (1985) and recent collection records (Grant pers. data).
Map of the North Americageographic range of the Transverse Lady Beetle (see long description below)
Long description for Figure 2

Map of the geographic range of the Transverse Lady Beetle, which occurs across Canada and the United States, from Newfoundland and Labrador to Virginia, and west to Alaska and California. Approximately 65 percent of its historical global range is within Canada.

Canadian range

The Canadian range of the Transverse Lady Beetle stretches from St. John’s, Newfoundland and Labrador, west to Vancouver Island. At the northernmost extent of its range the species occurs throughout Yukon and mainland Northwest Territories (Brown 1962; Gordon 1985; Grant pers. data) (Figure 2). Although there are no confirmed records, the species may also occur in Nunavut. The Canadian range for this species is based on historical and current collection records, although there are gaps in survey coverage across geographic regions and time.

Extent of occurrence and area of occupancy

Extent of occurrence (EOO) for the Transverse Lady Beetle is based on databased museum collections and recent surveys. Based on a minimum convex polygon within the extent of Canada’s jurisdiction, the EOO from 1889 – 2015 records is 10.6 million km2 (Figure 3). The EOO calculated from 1996 – 2005 records is 5.3 million km2 (Figure 4). The EOO calculated from 2006 – 2015 records is 6.9 million km2 (Figure 4). This is an estimated 30% increase in EOO over the previous decade.

Figure 3. Extent of occurrence (EOO: 10.6 million km2) and index of area of occupancy (IAO: 2884 km2) for the Transverse Lady Beetle (Coccinella transversoguttata) based on museum collections and recent surveys (1889 - 2015).
Map of Canada showing extent of occurrence (see long description below)
Long description for Figure 3

Map showing extent of occurrence (outlined) and observation records for the Transverse Lady Beetle in Canada, based on museum collections and recent surveys. The species’ range stretches from St. John’s, Newfoundland and Labrador, west to Vancouver Island, British Columbia. At the northernmost extent of its range the species occurs throughout Yukon and mainland Northwest Territories.

Figure 4. Extent of Occurrence (EOO) and Index of Area Occupancy (IAO) for the Transverse Lady Beetle (Coccinella transversoguttata). 1996 – 2005: EOO = 5.30 million km2, IAO = 76 km2. 2006 – 2015: EOO = 6.97 million km2, IAO = 144 km2. Trends in EOO and IAO for this species reflect issues with survey coverage and detection across its geographic range and over time, rather than expansion or retraction of its range.
Two map panels of Canadashowing showing extent of occurrence (see long description below)
Long description for Figure 4

Two map panels showing showing extent of occurrence (outlined) and observation records for the Transverse Lady Beetle in Canada for different periods: 1996 to 2005 (upper panel) and 2006 to 2015 (lower panel).

An index of area of occupancy (IAO) based on the databased museum collections and surveys from 1889 – 2015 is 2,884 km2 (Figure 3); 1996 – 2005 records is 76 km2 (Figure 4) and 2006 – 2015 records is 144 km2 (Figure 4). This is an estimated 89% change in IAO over the previous decade, due mainly to increased search effort.

Changes in EOO and IAO for this species reflect the lack of historical survey coverage and detection across its geographic range throughout time, rather than expansion or contraction of its range. Changes in EOO and IAO are therefore not considered reliable evidence of population trends (see Fluctuations and Trends for further discussion).

Search effort

Museum and collection records for the Transverse Lady Beetle date from 1889 – 2015. A database of over 23,000 lady beetle records (Coccinellidae), including 2,606 records for the Transverse Lady Beetle, has been compiled from 26 collections across Canada (see Collections Examined; Grant pers. data) (Table 1).

Table 1. There are 2,606 Transverse Lady Beetle specimens known from 1896 – 2015 in Canada (see Collections Examined).
ProvinceTotal CoccinellidaeTransverse Lady Beetle
Yukon Territory583133
Northwest Territories9048
British Columbia7017272
Alberta778182
Saskatchewan1793203
Manitoba2369323
Ontario6688934
Quebec1949219
New Brunswick658109
Nova Scotia686104
Prince Edward Island652
Newfoundland and Labrador8715
Unknown*33661
Total231002606

* Unknown Canadian location but specimens have date information

Insect collections are important sources for information on geographic distribution, especially for wide-ranging insects. However, collection records are generally not systematic or comprehensive over time or across geographic ranges, resulting in large areas and time periods with few data. In Canada most search effort has also been focused within agricultural systems or near urban centres, rather than in less disturbed habitats (Acorn 2007). Additionally, a number of collections across Canada are not currently databased, which creates additional gaps in information and past survey coverage.

Although the number of records for lady beetles are similar from 1996 – 2005 (2110 records) compared to 2006 – 2015 (1912 records), there has been an increased awareness of native lady beetle declines across Canada over the last decade. This awareness has translated into greater search effort for this species over the last decade. Nevertheless, gaps in search effort still remain.

In preparation for this status report, sites that had recent records of the Transverse Lady Beetle were re-visited and surveys were carried out within geographic survey gaps, including remote natural areas in northern BC, AB, YT and NT. There were 285 sites searched in 2013 to 2015 for a total search effort of over 296 hours (Table 2, Figure 5). For a conspicuous, easily collected beetle, this represents a relatively large search effort per site. A total of 75 specimens were found at 20 sites within known regions for Transverse Lady Beetles, including Newfoundland and Labrador, BC, YT and NT. The Canadian Wildlife Service in Yukon, and the Government of the Northwest Territories, also conducted recent surveys specifically for the Transverse Lady Beetle, which are included in search effort (Leung 2016). Search effort during the preparation of this status report resulted in 75 (71%) of the 105 recorded specimens of Transverse Lady Beetle collected from 2006 – 2015.

Table 2. Target search effort 2013 – 2015. Total search effort of 291.3 hours across 280 sites detected 64 Transverse Lady Beetles (Grant pers. data).
Prov.PlaceYearMinTLB*Surveyor
YTWhitehorse201430noHeron J
YTWhitehorse201445noHeron J
YTWhitehorse201415noHeron J; Sheffield C
YTWhitehorse201415noHeron J; Sheffield C
YTWhitehorse2015601Leung M
YTWhitehorse2015601Leung M
YTWhitehorse2015605Leung M
YTWhitehorse2015601Leung M
YTWhitehorse2015603Leung M
YTWhitehorse201551Coleman S; Bennett B
NTFort Simpson201430noAllaire D
NTFort Simpson201430noAllaire D
NTFort Simpson20146021Allaire D
NTFort Simpson2014302Allaire D
NTFort Simpson2014302Allaire D
NTFort Simpson201430noAllaire D
NTHay River20145noSmith G
NTJean Marie River201430noAllaire D
NTJean Marie River2015305Allaire D
NTWrigley201430noAllaire D
NTWrigley201430noAllaire D
NTWrigley2014303Allaire D
NTWrigley201430noAllaire D
NTYellowknife20145noKalnay-Watson S
NTYellowknife201451Kalnay-Watson S
NTYellowknife201451Pike E
BCArras201390noCopley C; Copley D; Heron J; Gartner H
BCArras201335noCopley C; Copley D; Heron J; Gartner H
BCAshnola River Valley201415noHeron J;
BCAttachie2013462noCopley C; Copley D; Heron J; Gartner H
BCAttachie201390noCopley C; Copley D; Heron J; Gartner H
BCBrisco201415noGrant P
BCChetwynd2013120noCopley C; Copley D; Heron J; Gartner H
BCChetwynd201390noCopley C; Copley D; Heron J; Gartner H
BCClinton2013140noCopley C; Copley D; Heron J; Gartner H
BCComox201495noHeron J
BCCoquihalla201530noGrant P
BCCoquihalla Lake2013120noCopley C; Copley D; Heron J; Gartner H
BCDelta201415noHeron J
BCDenman Island201415noHeron J
BCDenman Island201415noHeron J
BCDenman Island201415noHeron J
BCDenman Island201415noHeron J
BCFairmont Hot Springs201415noGrant P
BCFairmont Hot Springs201415noGrant P
BCFort St. John201315noCopley C
BCFort St. John2013124noCopley C; Copley D; Heron J; Gartner H
BCFort St. John2013420noCopley C; Copley D; Heron J; Gartner H
BCFort St. John201353noCopley C; Copley D; Heron J; Gartner H
BCFort St. John2013210noCopley C; Copley D; Heron J; Gartner H
BCFort St. John2013435noCopley C; Copley D; Heron J; Gartner H
BCFort Ware201415noBennett R; Copley C; Copley D;
BCGaliano Island201430noOtt L
BCGreater Victoria201415noHeron J
BCGreater Victoria201415noHeron J
BCGreater Victoria201415noN/A
BCHaida Gwaii201460noMcClaren E.
BCHaida Gwaii201530noWijdeven B.
BCHaida Gwaii201530noWijdeven B.
BCHaida Gwaii201530noWijdeven B.
BCHaida Gwaii201530noWijdeven B.
BCHaynes Lease2013630noSheffield C; Weston M; Heron J
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHazelton201460noWestcott L
BCHixon2013140noCopley C; Copley D; Heron J; Gartner H
BCHope20131203Copley C; Copley D; Heron J; Gartner H
BCHudson’s Hope2013120noCopley C; Copley D; Heron J; Gartner H
BCHudson’s Hope201374noCopley C; Copley D; Heron J; Gartner H
BCHudson’s Hope201325513Copley C; Copley D; Heron J; Gartner H; Cannings S
BCHudson’s Hope20133608Copley C; Copley D; Heron J; Gartner H
BCInkaneep Prov. Park2013360noSheffield C, Weston M; Heron J
BCIona Beach Park2014301Cesselli S; Turner S
BCIona Beach Park2014301Cesselli S; Turner S
BCKakwa Prov. Park2014115noRamey B; Ramey B
BCKakwa Prov. Park20145noRamey B; Ramey B
BCKakwa Prov. Park201410noRamey B; Ramey B
BCKakwa Prov. Park201410noRamey B; Ramey B
BCKakwa Prov. Park201410noRamey B; Ramey B
BCKakwa Prov. Park201415noRamey B; Ramey B
BCKakwa Prov. Park201410noRamey B; Ramey B
BCKakwa Prov. Park201460noRamey B; Ramey B
BCKakwa Prov. Park20145noRamey B; Ramey B
BCKamloops201515noGrant P
BCKamloops201530noGrant P
BCKeily Prov. Park201415noBennett R; Copley C; Copley D
BCKeily Prov. Park201415noCopley C; Copley D
BCKeily Prov. Park201415noBennett R; Copley C; Copley D
BCLower Mainland201430noN/A
BCLower Mainland201430noN/A
BCLower Mainland201430noN/A
BCMayne Island201430noDunn M
BCMayne Island201430noDunn M
BCMayne Island201430noDunn M
BCMayne Island201430noDunn M
BCMerritt2013120noCopley C; Copley D; Heron J; Gartner H
BCMerritt201530noGrant P
BCMeziadin Junction201460noWestcott L
BCMt. Kobau2013180noSheffield C; Gardiner L; Dyer O; Heron J
BCMt. Kobau201415noCopley C; Copley D; Heron J;
BCMt. Kobau201415noCopley C; Copley D; Heron J;
BCMt. Kobau201415noCopley C; Copley D; Heron J;
BCMt. Kobau201415noCopley C; Copley D; Heron J;
BCMt. Kobau201415noCopley C; Copley D; Heron J;
BCMt. Kobau201415noCopley C; Copley D; Heron J;
BCNahatlach201360noHeron J; Lynch G
BCNahatlach201315noHeron J; Lynch G
BCNahatlach201330noHeron J; Lynch G
BCNahatlach201330noHeron J; Lynch G
BCNorthern BC201460noHeron J
BCNorthern BC2014150noHeron J
BCNorthern BC201430noHeron J
BCNorthern BC201415noHeron J; Sheffield C
BCNorthern BC201415noHeron J; Sheffield C
BCNorthern BC201415noHeron J; Sheffield C
BCNorthern BC201415noHeron J; Sheffield C
BCNorthern Vancouver I201415noCopley C; Copley D; Heron J; Gartner H
BCNorthern Vancouver I201415noCopley C; Copley D; Heron J; Gartner H
BCOkanagan Falls201475noHeron J; Burdock N
BCOsoyoos201415noCopley C; Copley D; Heron J;
BCOsoyoos201415noCopley C; Copley D; Heron J;
BCOsoyoos201415noCopley C; Copley D; Heron J;
BCOsoyoos201415noCopley C; Copley D; Heron J;
BCOsoyoos2013120noHeron J; Sheffield C
BCOsoyoos201340noHeron J; Sheffield C
BCPine River2013120noCopley C; Copley D; Heron J; Gartner H
BCPine River2013120noCopley C; Copley D; Heron J; Gartner H
BCPrince George2013160noCopley C; Copley D; Heron J; Gartner H
BCPrince George201390noCopley C; Copley D; Heron J; Gartner H
BCPrince George2013140noCopley C; Copley D; Heron J; Gartner H
BCPrince George201399noCopley C; Copley D; Heron J; Gartner H
BCPrinceton201430noHeron J
BCQuesnel2013180noCopley C; Copley D; Heron J; Gartner H
BCQuesnel201370noCopley C; Copley D; Heron J; Gartner H
BCRussel Prov. Park201415noCopley C; Copley D
BCRussel Prov. Park201415noCopley C; Copley D
BCRussel Prov. Park201415noBennett R; Copley C; Copley D
BCRussel Prov. Park201415noBennett R; Copley C; Copley D
BCSage Sparrow Grasslands2013360noHeron J; Sheffield C
BCSimilkameen201380noHeron J; Sheffield C
BCSmithers201460noWestcott L
BCSmithers201460noWestcott L
BCSmithers201460noWestcott L
BCSmithers201460noWestcott L
BCSmithers201460noWestcott L
BCSooke201415noGrant P
BCSouth201415noHeron J
BCSouth Okanagan201430noHeron J
BCSouth Okanagan201430noHeron J
BCSouth Okanagan201430noHeron J
BCSouth Okanagan201430noHeron J
BCSouth Okanagan201430noHeron J
BCSouth Okanagan201430noHeron J
BCSouth Okanagan201415noHeron J
BCSouth Okanagan201430noHeron J; Sandhu J
BCSouth Okanagan201430noHeron J; Sandhu J
BCSouth Okanagan201430noHeron J; Sandhu J
BCSouth Okanagan201430noHeron J; Weston W; Bunge S; Pope B
BCSouth Okanagan201415noHeron J; Sandhu J
BCSouth Okanagan2013280noSheffield C; Gardiner L; Dyer O; Heron J
BCStrathcona Prov. Park201415noBennett R; Copley C; Copley D; Heron J; McClaren E
BCStrathcona Prov. Park201415noBennett R; Copley C; Copley D; Heron J; McClaren E
BCSydney201460noHeron J; Gelling L
BCTatton2013128noCopley C; Copley D; Heron J; Gartner H
BCTaylor201340noCopley C; Copley D; Heron J; Gartner H
BCThompson Region201430noLetay S
BCTranquille20145noHowie R
BCTsay Keh201415noBennett R; Copley C; Copley D
BCTsay Keh201415noBennett R; Copley C; Copley D
BCTsay Keh201415noBennett R; Copley C; Copley D
BCTumbler Ridge201370noCopley C; Copley D; Heron J; Gartner H
BCVancouver Island201430noCasselli S; Turner S
BCVancouver Island201415noHeron J
BCVancouver Island201415noHeron J
BCVaseux Lake Prov. Park201360noHeron J; Sheffield C
BCVictoria201415noHeron J; Gelling L
BCVictoria201415noGrant P
BCVictoria201415noGrant P
BCVictoria201530noGrant P
BCVictoria201530noGrant P
BCVictoria201530noGrant P
BCWhiskers Point Prov. Park201310noCopley C; Copley D; Heron J; Gartner H
BCWhite Lake Prov. Park2013315noSheffield C; Dyer O; Heron J
BCWilliams Lake201430noCoot K
BCWilliams Lake201460noCoot K; Foot T
BCWilliams Lake2013132noCopley C; Copley D; Heron J; Gartner H
BCWilliams Lake201380noCopley C; Copley D; Heron J; Gartner H
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201415noGrant P
ABCalgary201515noGrant P
ABCalgary201515noGrant P
ABCalgary201515noGrant P
ABCold Lake201415noGrant P
ABCold Lake201415noGrant P
ABCold Lake201415noGrant P
ABCold Lake201415noGrant P
ABConklin201415noGrant P
ABConklin201415noGrant P
ABConklin201415noGrant P
ABConklin201415noGrant P
ABConklin201415noGrant P
ABEdmonton201430noAnweiler G
ABGrande Prairie201415noGrant P
ABGrande Prairie201415noGrant P
ABGrande Prairie201415noGrant P
ABGrande Prairie201415noGrant P
ABGrande Prairie201415noGrant P
ABMclean Creek201415noGrant P
ABMedicine Hat201430noLeibel H
ABMedicine Hat201415noBuck M
ABSherwood Park201430noAnweiler G
ABSherwood Park201430noAnweiler G
ABVulcan County201430noLeibel H
ABZama City201415noGrant P
ABZama City201415noGrant P
ABZama City201415noGrant P
ABZama City201415noGrant P
ABZama City201415noGrant P
ONAirport, Cockburn I.201490noFoster R; Harris A; Jones C
ONBatchawana Bay, Lake Superior201460noFoster R; Harris A; Jones C
ONBelanger Bay, Manitoulin I.2014105noFoster R; Harris A; Jones C
ONBlack’s Point Beach, Lake Huron201460noFoster R; Harris A; Jones C
ONBurnt I. Harbour, Manitoulin I.2014210noFoster R; Harris A; Jones C
ONCarroll Wood Bay, Manitoulin I.2014105noFoster R; Harris A; Jones C
ONCarter Bay, Manitoulin I.2014300noFoster R; Harris A; Jones C
ONDean’s Bay, Manitoulin I.2014270noFoster R; Harris A; Jones C
ONDominion Bay, Manitoulin I.2014120noFoster R; Harris A; Jones C
ONGreat Duck I.2014180noFoster R; Harris A; Jones C
ONKitchener20145noDay M
ONLonely Bay, Manitoulin I.2014150noFoster R; Harris A; Jones C
ONMisery Bay, Manitoulin I.2014180noFoster R; Harris A; Jones C
ONMississagi River mouth2014102noFoster R; Harris A; Jones C
ONMurphy Harbour, Manitoulin I.201430noFoster R; Harris A; Jones C
ONPancake Bay, Lake Superior2014210noFoster R; Harris A; Jones C
ONPic River Dunes, Lake Superior201448noFoster R; Harris A; Jones C
ONPinery Prov. Park, Lake Huron201436noFoster R; Harris A; Jones C
ONPoint Farms Prov. Park, Lake Huron2014180noFoster R; Harris A; Jones C
ONPortage Bay, Manitoulin I.2014180noFoster R; Harris A; Jones C
ONProvidence Bay, Manitoulin I.2014240noFoster R; Harris A; Jones C
ONSand (Hensly) Bay, Manitoulin I.201496noFoster R; Harris A; Jones C
ONSand Bay, Cockburn I.2014300noFoster R; Harris A; Jones C
ONShrigley Bay, Manitoulin I.2014165noFoster R; Harris A; Jones C
ONSquare Bay, Manitoulin I.2014105noFoster R; Harris A; Jones C
ONTaskerville, Manitoulin I.2014105noFoster R; Harris A; Jones C
QCChemin Choinière201460noBereczky V
QCChemin Magenta201460noBereczky V
QCLac Gale GR11201460noBereczky V
QCMont St-Hilaire2014120noBereczky V
QCPrairie Mt Aki2014120noBereczky V
QCMagdalen Islands201585noHeron J; Sheffield C
QCMagdalen Islands201545noHeron J; Sheffield C
QCMagdalen Islands2015135noHeron J; Sheffield C
QCMagdalen Islands2015110noHeron J; Sheffield C
QCMagdalen Islands201515noHeron J; Sheffield C
QCMagdalen Islands201545noHeron J; Sheffield C
QCMagdalen Islands201535noHeron J; Sheffield C
QCMagdalen Islands201510noHeron J; Sheffield C
QCMagdalen Islands201535noHeron J; Sheffield C
QCMagdalen Islands2015105noHeron J; Sheffield C
QCMagdalen Islands201545noHeron J; Sheffield C
QCMagdalen Islands201560noHeron J; Sheffield C
QCMagdalen Islands201554noHeron J; Sheffield C
QCMagdalen Islands201560noHeron J; Sheffield C
QCMagdalen Islands201530noHeron J; Sheffield C
QCMagdalen Islands201521noHeron J; Sheffield C
QCMagdalen Islands201539noHeron J; Sheffield C
QCMagdalen Islands201547noHeron J; Sheffield C
QCMagdalen Islands201560noHeron J; Sheffield C
NBHighway 15, Cap Pele exit201535noHeron J; Sheffield C
NSEagle Head20145noDurovich K
PESouris201545noHeron J; Sheffield C
PESouris201590noHeron J; Sheffield C
NLHappy Valley-Goose Bay201451Elson L
NLBlack Tickle201451Elson L

 

Figure 5. Search effort sites (orange) (2013 – 2015) and known sites (black) for the Transverse Lady Beetle (Coccinella transversoguttata). Search effort (within 120 km) overlapped with 1,489 (57%) known sites.
Map of Canada showing the locations of sites searched (see long description below)
Long description for Figure 5

Map showing the locations of sites searched for the Transverse Lady Beetle from 2013 to 2015 and all known records from 1899 to 2015.

The dispersal ability of Transverse Lady Beetle is unknown. However, based on potential dispersal ability (under ideal conditions) of other closely related (Coccinella) lady beetle species (see Dispersal and Migration) the species could fly 18 – 120 km in a single flight (Jeffries et al. 2013). These potential dispersal distances were used to estimate overlap between search effort and known databased sites of Transverse Lady Beetles. An 18 km radius around search effort sites overlapped with 497 known databased sites. A 120 km radius around search effort sites overlapped with 1,489 known databased sites (Figure 5). For such a broadly distributed, mobile species, this search effort represents relatively good search effort coverage of known sites for Transverse Lady Beetles.


Habitat

Habitat requirements

The Transverse Lady Beetle is a habitat generalist and known to occur within agricultural areas, suburban gardens, parks, coniferous forests, deciduous forests, prairie grasslands, meadows, and riparian areas. It was also one of the more dominant lady beetles found on agricultural crops including alfalfa, potatoes, corn, soybean, and cotton (Wheeler and Hoebeke 1995; Harmon et al. 2007; Losey et al. 2007; Gardiner et al. 2011; Hodek et al. 2012). The Transverse Lady Beetle can also be found in a wide variety of non-agricultural vegetation including birch (Betula spp.), pine (Pinus spp.), spruce (Picea spp.), maple (Acer spp.), mountain ash (Sorbus spp.), poplar (Populus spp.), willow (Salix spp.), sage (Salvia spp.), cherry (Prunus spp.), alder (Alnus spp.), thistles (Family Asteraceae), grasslands, and scruff pea (Family Fabaceae) plants along the edge of sand dunes (Wheeler and Hoebeke 1995; Acorn 2007; Harmon et al. 2007; Losey et al. 2007).

Transverse Lady Beetles move across these different habitats and vegetation to exploit seasonal changes in prey availability and their distribution is therefore driven to a large extent by prey availability rather than habitat type (Hagen 1962; Hodek and Honěk 1996; Sloggett and Majerus 2000; Hodek et al. 2012).

Overwintering adults tend to aggregate in well ventilated microhabitats such as under stones, rock crevices, in grass tussocks, in leaf litter, or in tree bark (Hodek and Honěk 1996; Hodek et al. 2012). Larvae tend to be located in habitat with an abundance of prey.

Habitat trends

The Transverse Lady Beetle has a large range in Canada spanning numerous ecozones and habitat types (Gordon 1985; Grant pers. data). This species also readily disperses short and long distances to exploit changes in prey availability over the season and across vegetation types. No studies have specifically related habitat trends to declines in Transverse Lady Beetle subpopulations. It is therefore unknown if specific habitat trends have caused this particular lady beetle, with its wide diet and habitat range, to decline historically over much of its known range across Canada.

However, in recent decades, the capacity of agricultural landscapes to provide habitat for wildlife has declined significantly across Canada’s ecozones (Federal, Provincial and Territorial Governments of Canada 2010; Javorek and Grant 2011). One cause for this is more intensive use of agricultural land. This includes heavier reliance on chemicals for pest control (see Threats), which presumably negatively affect Transverse Lady Beetles directly, or indirectly by impacting their prey.

Conversion of managed lands and farms resulting in regrowth of forest could also result in less favourable foraging for the Transverse Lady Beetle (Harmon et al. 2007; Bucknell and Pearson 2007). This slow natural succession has mainly occurred in areas of Eastern Canada (see Threats).

While large scale changes in habitat and prey availability suggest a possible explanation, there are no data to demonstrate causality between a changing landscape and lady beetle densities (Elliott and Kieckheffer 1990; Elliott et al. 1999; Harmon et al. 2007).


Biology

In general, little is known on the biology of Transverse Lady Beetles. Information below is compiled from general lady beetle references from closely related species (Coccinella) (Acorn 2007; Hodek et al. 2012). Where applicable, references are provided specifically for Transverse Lady Beetles.

Life cycle and reproduction

Lady beetles are holometabolous, meaning they have a complete metamorphosis and pass through egg, larva, pupa and adult stages. No studies have been conducted regarding the lifespans of adult Transverse Lady Beetles, but closely related species generally have a lifespan of 20 to 60 days (McMullen 1967). The Transverse Lady Beetle can have two generations per year depending on regional climatic conditions (Hodek et al. 2012). Adults of the spring generation can undergo aestivation, a type of dormancy, to avoid high summer temperatures, and lay eggs in early autumn (Hodek et al. 2012). Adults of the autumn generation congregate overwinter and undergo another type of dormancy known as diapause, and only become active and reproduce when temperatures warm in the early spring (McMullen 1967; Hodek et al. 2012; Losey et al. 2012).

The eggs of lady beetles are typically tightly packed in an upright position in clusters of 20 to 30 eggs, on a range of plants that are likely to support subpopulations of aphids (Acorn 2007; Hodek et al. 2012). Over 14 days female Transverse Lady Beetles can lay approximately 267 eggs (Kajita et al. 2009). Many females also lay unfertilized eggs, along with the fertile eggs, as another food source for young larvae (Acorn 2007).

There is no information regarding the length of time it takes to develop from egg to adult for the Transverse Lady Beetle and development times are likely highly affected by prey availability and temperature. In closely related lady beetles, development from egg to adult typically takes 20 days (Ugine and Losey 2014). Larvae hatch from eggs after approximately 3 days followed by approximately 13 more days before reaching their fourth instar to pupate (Losey et al. 2012; Ugine and Losey 2014). After approximately 5 more days as a pupa, lady beetles emerge as adults (Ugine and Losey 2014). Typically, activity of the follicular tissue in the testes starts in the pupa, so mating can begin shortly after emerging (Acorn 2007; Hodek et al. 2012). Elytra harden one day after emerging and adults are then able to disperse. Female Transverse Lady Beetles secrete pheromones to attract males, and at close distances males rely on both chemical and visual cues (Losey et al. 2012). The Transverse Lady Beetle is polygynandrous, with both sexes mating with multiple partners (Omkar and Srivastava 2002; Srivastava and Omkar 2004; Acorn 2007). As in other lady beetles, the sex ratio is likely close to 1:1 and adults do not show exaggerated sexual dimorphism (Stellwag and Losey 2014). However, there can be variability in body size and weight, depending on food availability and regional climatic conditions. When food is scarce lady beetles will have smaller body sizes and weights, correlating to decreased survivorship over winter (Smith 1966).

Physiology and adaptability

Transverse Lady Beetles display aposematism, or bright warning colours to deter predators (Acorn 2007). Although undocumented, this species (similar to other lady beetles) is likely able to reflex bleed, releasing defensive alkaloids from tibio-femoral joints when provoked (Hodek et al. 2012). There are about 50 different alkaloids that have been identified in lady beetles (Laurent et al. 2005). The various alkaloid compositions across species also vary in respect to their effects on predators (Marples et al. 1989; Laurent et al. 2005; Hodek et al. 2012).

Transverse Lady Beetles also occupy a wide ecological niche across a variety of temperature regimes in Canada; they are cold-tolerant and adults are able to overwinter. This plasticity also enables this species to exploit seasonal changes in prey availability across different habitats and vegetation (Hodek et al. 2012).

Dispersal and migration

Little is known on the natural dispersal rates specifically for the Transverse Lady Beetle. In general lady beetles are very mobile, display low site fidelity, and readily engage in short (few hundred metres) and long (18 – 120 km) distance dispersal (van der Werf 2000; Acorn 2007; Hodek et al. 2012). The ability to disperse relatively long distances has resulted in high rates of gene flow between subpopulations (Krafsur et al. 2005) and enables lady beetles to exploit changes in prey availability (Hodek et al. 2012).

Drivers of dispersal are a combination of prey density and environmental variables such as temperature, wind speed and rainfall (Ives et al. 1993; Hodek and Honěk 1996; van der Werf 2000; Cardinale et al. 2006; Krivan 2008; Jeffries et al. 2013). Previous work has also shown that lady beetle emigration decreases with increasing prey abundance (Ives 1981; Ives et al. 1993; Elliott 2000; van der Werf 2000; Cardinale et al. 2006; Jeffries et al. 2013) and the density of adult lady beetles is positively correlated with aphid density (Turchin and Kareiva 1989; Hodek and Honěk 1996; Osawa 2000; Evans and Toler 2007).

Calculating dispersal rates over long distances has generally been problematic due to the difficulty of tracking insects in the field. One study used vertical-looking entomological radars to determine dispersal distance of non-native Seven-spotted Lady Beetles (Coccinella septempunctata) and Multicolored Asian Lady Beetle (Harmonia axyridis). This study determined that the majority of these lady beetles fly at 150 – 479 metres above ground level (m AGL) perhaps due to decreasing air temperatures and increasing energetic requirements of reaching higher altitudes (Jeffries et al. 2013). Mean flight speed of these lady beetles ranged from 31 km/h at 150 m AGL to 59 km/h at 1500 m AGL (Jeffries et al. 2013). Using tethered flight experiments, this study also estimated a mean flight time of 36.5 minutes, with a maximum of 2 hours (Jeffries et al. 2013). Extrapolating from these results it was estimated that with ideal meteorological conditions, lady beetles could fly 18 km in a single flight (30 km/h for 36.5 minutes) and a few individuals flying at high altitudes and speeds (59 km/h for two hours) could potentially fly 120 km in a single flight (Jeffries et al. 2013). As these non-native lady beetles are of similar size and in the case of the Seven-spotted Lady Beetle closely related, it is likely these dispersal distances are comparable for other native lady beetles.

Interspecific interactions

Both adult and larval stages of the Transverse Lady Beetle prey primarily on a wide variety of aphids (Acorn 2007; Hodek et al. 2012). Typically, lady beetles also prey on other small insects and eggs including spider mites, alfalfa weevils, leafhoppers, scale insects, psyllids, lepidopteran eggs, in addition to sap, nectar and pollen (Wheeler and Hoebeke 1995; Acorn 2007; Hesler et al. 2012). Transverse Lady Beetles, like other lady beetle species, are generalists in food and habitat use, often responding to changes in aphid abundance across many types of habitats (Hagen 1962; Hodek and Honěk 1996; Sloggett and Majerus 2000). Lady beetles can also be attracted to aphid densities of below 10 individuals per square metre, and even volatiles produced by herbivore-injured plants (Hodek et al. 2012).

The Transverse Lady Beetle is subject to intraguild competition and predation by other introduced lady beetles (Turnipseed et al. 2014). There is a broad coincidence between shrinkage of geographic range and subpopulation declines for native lady beetles with the introduction and spread of the Seven-spotted Lady Beetle and the Multicolored Asian Lady Beetle. A direct causal link is not obvious, though potential mechanisms include direct competition for food, intraguild predation, and spread of new parasitoids or pathogens. Competition is also suspected to have led to declines in the body size of other native lady beetles (Losey et al. 2012), likely reducing their survivorship over winter (Smith 1966) (see Threats).

General predation on lady beetles by vertebrates such as birds is reduced by aposematic warning colours and distasteful defensive alkaloids excreted by reflex-bleeding from the tibio-femoral joints (Laurent et al. 2005; Acorn 2007; Hodek et al. 2012). Despite these defences, lady beetles have been reported to be eaten by a wide range of vertebrate and invertebrate predators (Acorn 2007; Hodek et al. 2012). Web-building spiders are also frequently reported preying on lady beetles (Nentwig 1983; Richardson and Hanks 2009; Sloggett 2010).

Lady beetles, in general are parasitized by various tachinid flies, phorid flies, chalcidoid wasps, parasitic mites, nematodes, sporazoans, fungi and bacteria (Wheeler and Hoebeke 1995; Acorn 2007; Bjornson 2008; Roy and Cottrell 2008; Hodek et al. 2012).

The braconid wasp Dinocampus coccinellae is the main parasitoid of numerous lady beetle species, including the Seven-spotted Lady Beetle and the Multicolored Asian Lady Beetle, and can likely cause substantial reductions in subpopulations of the Transverse Lady Beetle (Ceryngier and Hodek 1996; Abassi et al. 2001; Acorn 2007; Hodek et al. 2012). This braconid wasp currently has a cosmopolitan distribution covering all continents except Antarctica, and many islands (Hodek et al. 2012). The natural geographic range of D. coccinellae is difficult to reconstruct as it is believed this species arrived in some parts of its present distribution with ladybirds released for biological control purposes (Hodek et al. 2012).

Other interspecific interactions include parasitic mites (i.e., Coccipolipus hippodamiae), fungal pathogens (i.e., Beauveria bassiana), microsporidia (Nosematidae) and bacteria, which can all negatively impact lady beetle fitness and reduce survivorship over winter (Cali and Briggs 1967; Hurst et al. 1995; Barron and Wilson 1998; Webberley and Hurst 2002; Webberley et al. 2004).


Population sizes and trends

Sampling effort and methods

Multiple datasets from museum and private collections across Canada (see Collections Examined) were used to assess overall patterns of change in geographic distribution and relative abundance of the Transverse Lady Beetle. The collated dataset contains over 23,000 records of Coccinellidae from 1889 to 2015, including 2,606 Transverse Lady Beetle specimens. Numerous collections were also visited by McCorquodale et al. (2011) to identify and verify Coccinellidae specimens, before specimen label information was databased. Subsequently, additional museum and specimen data were compiled from surveys and collections for the preparation of this status report (Grant pers. data). Localities were georeferenced so that species could be mapped using geographic information systems (GIS) software. Latitude and longitude were taken from labels when available, but for other specimens, the generalized latitude and longitude of the town centre on the label was used, unless a more specific locality could be determined. In addition, from 2013 to 2015 there were over 296 hours of field surveys conducted across 285 sites incorporated within this database (Table 2).

Insect collections are important sources for information on geographic distribution of species (Wiggins et al. 1991). Specimens within Canadian collections have been collected by a combination of professional entomologists, students and keen amateurs during biodiversity inventories, general collections, taxon specific collections, ecological studies and applied studies on crops and forests.

Data from collections can help delineate geographic ranges of lady beetles and assess temporal changes in distribution and abundance if the strengths and weaknesses of collection data are understood and considered. One weakness for broadly distributed insects across Canada is that collections have not been consistent throughout time or geographic range. In addition, there are a number of collections across the country which do not have specimen information databased, resulting in further information gaps. Collections can also be time series biased and may not reflect the true abundance of a species as experts may not continue to collect specimens of common lady beetles. Conversely, newly introduced and invasive species might be collected out of proportion to the actual relative abundance of the Transverse Lady Beetle (McCorquodale et al. 2011).

Due to associated biases, accurately documenting changes in the geographic distribution of a species over time is a difficult task (Fortin et al. 2005; Elith et al. 2006; Koch and Strange 2009). Maps of geographic distribution over time may show a decrease in geographic range when in fact they reflect a decrease in subpopulation size, because with reduced subpopulations there is a decrease in probability of collection (McCorquodale et al. 2011). Conversely, an increase in geographic range can also reflect greater search effort, rather than an increase in subpopulation size. Trends in extent of occurrence (EOO) and index of area of occupancy (IAO) are therefore biased by search effort, which has not been consistent over time or over the range of this species.

Trends in absolute abundance are also biased by search effort. Therefore, relative abundance or the percent composition of a particular species relative to the total number of species is a common approach used to measure insect populations and reduce bias with search effort. For the Transverse Lady Beetle collection records are compared to all lady beetles (Coccinellidae) collected across similar time periods and geographic range as a proxy of abundance. In addition, collection records are also compared to only native lady beetles collected. As non-native species can potentially experience rapid subpopulation expansion and growth, inclusion of non-native species may produce artificially inflated declines. Conversely, as many species of native lady beetles are in decline across Canada, their use in measures of relative abundance may underestimate declines.

Abundance

Estimating abundance of total number of mature individuals for a wide-ranging species, such as the Transverse Lady Beetle, is not possible with current available data. Extent of occurrence (EOO), index of area of occupancy (IAO), and relative abundance were therefore used to measure trends. In addition, these data were supplemented by published research and expert opinion documenting subpopulations and range declines of the Transverse Lady Beetle in North America.

Fluctuations and trends

Natural population fluctuations in lady beetle subpopulations are related to dispersal, prey availability, climatic conditions and overwinter survivorship. Lady beetles, including the Transverse Lady Beetle, do not experience extreme fluctuations.

Based on all databased records and surveys (1889 – 2015), the Transverse Lady Beetle has a total EOO of 10.6 million km2 and IAO of 2,884 km2 (Figure 3). During 1996 – 2005 the EOO was calculated as 5.3 million km2 with an IAO of 76 km2 (Figure 4). During the last decade (2006 – 2015) the EOO increased to 6.9 million km2 with a concurrent increase in IAO of 144 km2 (Figure 4). This is an estimated 30% change in EOO and 89% change in IAO from the previous decade.

As this is a broadly distributed species across Canada, and surveys have not been spatially or temporally complete, trends in this species’ geographic distribution therefore reflect issues with survey coverage or detection rather than expansion or contraction of its range. The increase in EOO and IAO are therefore directly related to recent search effort for this species. Search effort for this status report resulted in 75 of the 105 (71%) of recorded specimens for the 2006 – 2015 time period. Without this recent search effort IAO would have been similar to the previous decade (32 records in 1996 – 2006 vs. 30 records in 2006 – 2015). Correspondingly, it is also reasonable to assume that EOO has not changed significantly over the last two decades. Recent search effort has resulted in this species being detected in Labrador, where little search effort had been conducted in the previous decade. This significantly contributed toward an artificially low EOO for (1996 – 2005) and a false increase in EOO during the last ten years (2006 – 2015). Trends in EOO and IAO for this species are therefore biased by search effort, and are not reliable to assess trends across its entire Canadian range.

Historically the Transverse Lady Beetle was widely distributed, occurring across all Canadian provinces and territories. Nationally, it was also one of the more common lady beetles collected before 1985 (Brown 1940; Gordon 1985). From 1916 to 1975 the relative abundance of the Transverse Lady Beetle gradually increased each decade, dropping marginally in 1976 to 1985, corresponding to the same time period the non-native Seven-spotted Lady Beetle increased in abundance (Figure 6, 7; Table 3). During subsequent decades the Transverse Lady Beetle declined significantly, concurrent with significant increases in abundance of non-native lady beetles, such as the Seven-spotted Lady Beetle and the Multicolored Asian Lady Beetle (Figure 6, 7; Table 3).

Figure 6. Changes in relative abundance of the native Transverse Lady Beetle (Coccinella transversoguttata), non-native Seven-spotted Lady Beetle (Coccinella septempunctata) and Multicolored Asian Lady Beetle (Harmonia axyridis) compared to all databased Coccinellidae in Canada from 1916 - 2015.
Chart illustrating changes in the abundance of the native Transverse Lady Beetle (see long description below)
Long description for Figure 6

Chart illustrating changes in the abundance of the native Transverse Lady Beetle, non-native Seven-spotted Lady Beetle (Coccinella septempunctata) and Multicolored Asian Lady Beetle (Harmonia axyridis) in relation to all databased Coccinellidae in Canada from 1916 to 2015.

Figure 7. Canadian distribution of the Transverse Lady Beetle (black dots) and non-native lady beetles (red dots) over time.
Four pairs of map panels illustrating the Canadian distribution of the Transverse Lady Beetle (see long description below)
Long description for Figure 7

Four pairs of map panels illustrating the Canadian distribution of the Transverse Lady Beetle (left-hand panels) and non-native lady beetles (right-hand panels) over four time periods: 1976 to 1985; 1986 to 1995; 1996 to 2005; and 2006 to 2015.

Table 3. Numbers of Lady Beetle specimens recorded over ten-year periods. Results for Transverse Lady Beetles (TLB), all lady beetles (All) and non-native (NN). Lady Beetles were used to calculate relative abundance (see Table 4). Specimens with known date of collection but unrecorded location are listed as unknown (?)
TimeTypeYTNTNUBCABSKMBONQCNBNSPENL?Total
1896-1905TLB---2-226------12
1896-1905All1--8621546693----5227
1896-1905NN---------------
1906-1915TLB---79-28--11---37
1906-1915All1--10432115478123--2234
1906-1915NN---------------
1916-1925TLB---336-417--4---64
1916-1925All-1-7584211341211679--31092
1916-1925NN------1-------1
1926-1935TLB---411364352216----137
1926-1935All---116075867173221465--31758
1926-1935NN------1-------1
1936-1945TLB---15812121886---36115
1936-1945All---38348131431701004612222431180
1936-1945NN-------11-----2
1946-1955TLB4--15301638136371760-110364
1946-1955All8--824518837672020298210-3422622
1946-1955NN----------1----
1956-1965TLB21-226419224737499-75464
1956-1965All147-7221239110811301702601361416132804
1956-1965NN-------163-1---20
1966-1975TLB12-1327425154881715226374
1966-1975All13-21179373337263947682525142022
1966-1975NN-------3684-----120
1976-1985TLB102--4313641033112215-14669
1976-1985All4807-570695334991549231625-1983996
1976-1985NN---1-1121384-3-34310
1986-1995TLB---405371442-3--1-232
1986-1995All71-101816281707822204343521233142
1986-1995NN---89-451284341061224-3-841
AVRG: 1976-2005TLB350-3183584104812-11311
AVRG: 1976-2005All1643-679453274971102187214211143083
AVRG: 1976-2005NN---714175233986521121597
1996-2005TLB21-10656-2-----32
1996-2005All51-44849168285935127226523-2110
1996-2005NN---195142080671688572--1115
2006-2015TLB2244-311-1-3---3-105
2006-2015All6670-733192103562262736284407-1912
2006-2015NN61-334967242154220225737--1041

In the last decade (2006 – 2015) 54% of lady beetles collected in Canada were non-native and 82% of these non-native species were the Seven-spotted Lady Beetle and the Multicolored Asian Lady Beetle (Table 4). The abundance of non-native lady beetles varies across Canada (Figure 6, Table 4). Northern regions tend to have a lower proportion of non-native to native species (e.g., YT 9%, NT 1%). In Western Canada, BC (46%) and AB (50%) have a fairly even proportion of native to non-native lady beetles, compared to SK (70%) and MB (75%). Eastern Canada also has much higher proportions of non-native species (e.g., ON 68%, QC 81%, NS 68%, PE 93%). This trend was reflected in recent search effort in the Yukon, where collection at five sites resulted in 5 non-native lady beetles out of 55 native lady beetles (9%) (Leung 2016). In Quebec search effort collection at four sites resulted in over 280 lady beetles, of which 99% were non-native (86% Multicolored Asian Lady Beetles, 13% Seven-spotted Lady Beetles), demonstrating a continued dominance of non-native lady beetles in this region.

Table 4. Percent change in relative abundance (RA) over two decades, of the Transverse Lady Beetle (TLB) to all lady beetles (Coccinellidae) (native and non-native species) collected in Canada.
Prov1976-2005
RA All
1976-2005
RA Native
1996-2005
RA All
1996-2005 RA Native2006-2015
RA All
2006-2015 RA Native% Change 1976-2015 All% Change 1976-2015 Native% Change 1996-2015 All% Change 1996-2015 Native% Non-Native/
Native
2006-2015
YT0.210.210.400.400.330.375873-17-89
NT0.110.111.001.000.630.64466474-37-361
NU-----------
BC0.050.050.020.040.040.08-746899746
AB0.180.200.120.170.010.01-97-95-96-9450
SK0.110.120.030.030.000.00-100-100-100-10070
MB0.170.200.020.030.020.07-89-64-1514475
ON0.090.16-----100-100--68
QC0.040.080.020.030.010.06-74-28-306781
NB0.060.10-----100-100--35
NS0.040.12-----100-100--68
PE0.000.00--------93
NL0.060.070.000.000.430.43629500---
Total0.100.130.020.030.050.12-46-1026227554

In the last decade (2006 – 2015) there were 105 specimens of the Transverse Lady Beetle collected, compared to 32 specimens from the previous decade. This increase is due directly to increased search effort for this species (especially in the west and north), and does not reflect an actual increase in the Canadian population size.

Following increased search effort, relative abundance of Transverse Lady Beetles over the last decade increased nationally from 0.02 (1996 – 2005) to 0.05 (2006 – 2015) (compared to native and non-native lady beetles collected) and 0.03 (1996 – 2005) to 0.12 (2006 – 2015) (compared to native lady beetles collected). This is a positive change of 262% and 275% respectively. However, this national trend is largely driven by an increase in Transverse Lady Beetles collected in the YT and NT, where relatively little search effort for lady beetles had been conducted in the previous decade (1996 – 2005) and where relative abundance of this species appears to be substantially higher than in other parts of Canada.

Due to large variation in survey coverage, relative abundance of Transverse Lady Beetles over the last decade (2006 – 2015) was also compared to an average of the previous three decades (1976 – 2005). This resulted in relative abundance decreasing nationally by 46% (compared to native and non-native lady beetles collected) and 10% (compared to native lady beetles collected). The only regions in Canada that had higher percent relative abundances were YT, NT and BC (Table 4).

Looking at the number of specimens recorded across Canada from a historical context, out of the 13 provinces and territories where this species was historically abundant, it is no longer detected in 5 provinces (SK, ON, NB, NS and PE [although only two specimens have been databased for PE]). This species was last recorded in SK in 2001, ON in 1987, NB in 1994, NS in 1984, and PE in 1969. Furthermore, over the last ten years this species has only been recorded in low numbers in 4 other provinces (AB, MB, QC, and NL). In AB one specimen was recorded in 2012, in MB one specimen was recorded in 2015, in QC two specimens were recorded in 2006 and one in 2012, in NF and LB three specimens were recorded in 2014. Comparatively, 22 specimens were collected in YT, mainly in 2015, 44 specimens were collected in the NT in 2014, and 31 specimens were collected in BC, mainly in 2013. While no records exist in NU, given the prevalence of this species in YT and NT, it is also possible this species occurs here.

The consensus of expert opinion from the COSEWIC Arthropod Species Subcommittee is that the Transverse Lady Beetle has declined significantly historically, especially in regions where there is a high proportion of non-native lady beetles present (Figure 7). In the last decade, this species has remained undetected where it was formerly common (SK, ON, NB, NS, and likely PE) and is in decline or persisting in low numbers across the majority of its range (AB, MB, QC, NL). However, in BC, YT, NT and likely NU, this species remains common and these regions also seem to have a lower proportion of non-native species, which are considered a potential threat to the Transverse Lady Beetle.

McCorquodale et al. (2011) also reviewed evidence from literature and collection data from QC and ON to look at relative abundance and geographic ranges of a subset of 10 species of native and non-native lady beetles over time (<1960 – 2009). This study focused on regions with high quality data, complete over the time period non-natives arrived in Canada. Within this study McCorquodale et al. (2011) also showed that Transverse Lady Beetles declined in geographic range and in relative abundance by 72% from prior to 1960 to after 1980, concurrent with an increase in collection of non-native species.

Trends of decline in subpopulations of Transverse Lady Beetles and other native lady beetles after the arrival and establishment of non-native lady beetles are not restricted to Canada. In the United States, the Transverse Lady Beetle has also significantly declined, along with other lady beetles, which has been well documented by Wheeler and Hoebeke (1995). They highlighted studies that showed native species were common in many areas from the 1950s through 1970s, yet rarely encountered after 1985. Intensive surveys of lady beetles in Iowa, South Dakota, Minnesota, Michigan, Virginia and Maine all show that Transverse Lady Beetles and other native lady beetles were common and widespread prior to 1980, but are now very rare or extirpated (Elliott et al. 1996; Brown 2003; Alyokhin and Sewell 2003; Harmon et al. 2007; Hesler 2008; Hesler 2009; Koch 2011; Hodek et al. 2012; Bahlai et al. 2013; Bahlai et al. 2015).

In general, trends in the relative abundance of native to non-native lady beetle assemblages of Canada and the United States declined by 68% after 1985 (Harmon et al. 2007). A similar study conducted in Michigan over 24 years from 1989 to 2012 found lady beetle assemblages became increasingly non-native dominated with 71% of lady beetles collected being non-native (Bahlai et al. 2013). Gardiner et al. (2009) found that non-native Seven-spotted Lady Beetles and Multicolored Asian Lady Beetles accounted for up to 90% of lady beetle communities in soybean fields in Michigan, Wisconsin and Iowa. Tumminello et al. (2015) suggest declines of the native lady beetles can be attributed to the establishment, spread and subpopulation increase of the Seven-spotted Lady Beetle. While reasons for the decline in native lady beetles remain unclear, there is a very clear and real trend in declines of native lady beetles across their range, including the Transverse Lady Beetle.

In summary, this once historically common lady beetle now appears to be rare and with a more restricted range. Declines in relative abundance and geographic range have been documented in numerous studies throughout the Transverse Lady Beetle’s range across Canada and the United States (Staines et al. 1990; Wheeler and Hoebeke 1995; Elliott et al. 1996; Marshall 1999; Stephans 2002; Brown 2003; Acorn 2007; Harmon et al. 2007; Hesler and Kieckhefer 2008; Fothergill and Tindall 2010; Skinner and Domaine 2010; Evans et al. 2011; Koch 2011; McCorquodale et al. 2011). Within Canada, the relative abundance of the Transverse Lady Beetle has been significantly reduced compared to historical levels and extent. Over the last ten years, the Transverse Lady Beetle has continued to decline or is managing to persist in low numbers across the majority of its range, with the exception of BC, YT, NT and likely NU, where this species appears common and somewhat isolated from the impact of non-native species.

Rescue effect

The Transverse Lady Beetle is broadly distributed and its range extends into the United States from coast to coast. As this species is highly mobile and readily disperses, subpopulations could potentially disperse and recolonize areas where the Transverse Lady Beetle has declined, provided suitable habitat was available. However, as this species has also declined in the United States, and the reasons for the decline remain unknown, it is unlikely that rescue effect is possible.


Threats and limiting factors

The International Union for the Conservation of Nature - Conservation Measures Partnership (IUCN-CMP) threats calculator (see Salafsky et al. 2008; Master et al. 2009) was used to classify and list threats to the Transverse Lady Beetle (Appendix 1). Overall threat impact for the Transverse Lady Beetle is High – Medium. Potential or suspected threats below are listed on order of highest to lowest threat.

Threat 8. Invasive and other problematic species and genes (high to medium impact)

8.1 Invasive non-native/alien species

It has been widely reported that the accidental and intentional introduction of non-native species can negatively impact flora and fauna (New 1995; Cottrell and Shapiro-Ilan 2003; Evans 2004; Snyder and Evans 2006; Finlayson et al. 2008; Kenis et al. 2008; Kajita and Evans 2009; Crowder and Snyder 2010; Smith and Gardiner 2013; Ugine and Losey 2014; Tumminello et al. 2015). Insect generalist predators have been introduced outside their native range inadvertently or intentionally as biocontrol agents during the last century (Obrycki and Kring 1998; Mack et al. 2000; Evans et al. 2011). In North America alone, at least 179 non-native lady beetle species have been introduced, leading to nine non-native species becoming well established in Canada, including the Seven-spotted Lady Beetle and the Multicolored Asian Lady Beetle (Gordon 1985; Gordon and Vandenberg 1991; Harmon et al. 2007; Evans et al. 2011; McCorquodale et al. 2011; Bousquet et al. 2013). These non-native species continue to be widely available and released for biocontrol.

Significant declines in geographic range and abundance of native lady beetles are frequently due to changes in habitat or interactions with non-native species (New 1995; Cottrell and Shapiro-Ilan 2003; Evans 2004; Snyder and Evans 2006; Finlayson et al. 2008; Kenis et al. 2008; Kajita and Evans 2009; Crowder and Snyder 2010; Smith and Gardiner 2013; Ugine and Losey 2014; Tumminello et al. 2015).

The invasion of the Seven-spotted Lady Beetle and Multicolored Asian Lady Beetle into North America has been implicated in an overall reduction in the Transverse Lady Beetle and other native lady beetle subpopulations (Wheeler and Hoebeke 1995; Elliott et al. 1996; Marshall 1999; Ellis et al. 1999; Brown 2003; Cottrell and Shapiro-Ilan 2003; Turnock et al. 2003; Hesler et al. 2004; Acorn 2007; Harmon et al. 2007; Hesler and Kieckhefer 2008; Fothergill and Tindall 2010; Skinner and Domaine 2010; Evans et al. 2011; Losey et al. 2012; Comont et al. 2013; Turnipseed et al. 2014; Ugine and Losey 2014; Tumminello et al. 2015). Most explanations for this reduction in native subpopulations focus on negative interactions through competition, intraguild predation or indirect effects such as the introduction of pathogens (Schaefer et al. 1987; Ehler 1990; Cottrell and Shapiro-Ilan 2003; Louda et al. 2003; Evans 2004; Lucas 2005; Snyder and Evans 2006; Lucas et al. 2007; Kenis et al. 2008; Riddick et al. 2009; Evans et al. 2011; Turnipseed et al. 2014; Ugine and Losey 2014; Tumminello et al. 2015).

Competition and intraguild predation:

In support of scramble competition, where a finite resource is accessible to all competitors, it has been shown that Seven-spotted Lady Beetles were more voracious, had a higher aphid attack rate and lower aphid handling time, under a wide variety of conditions, compared with other native lady beetles (Hodek and Michaud 2008; Hoki et al. 2014). Tumminello et al. (2015) also investigated scramble competition and intraguild predation, concluding that the displacement of lady beetles from their native range was likely driven by the Seven-spotted Lady Beetle, based on its faster development times, higher attack rate, larger body size and high rate of intraguild predation.

Competition with Seven-spotted Lady Beetles has resulted in limited prey availability and decreased body size of other native lady beetles (Evans 2004; Losey et al. 2012). Furthermore, other studies have shown Seven-spotted Lady Beetles and Multicolored Asian Lady Beetles reduce survivorship of Transverse Lady Beetles and other native lady beetles, as a result of higher predation rates on their eggs and larvae (Obrycki et al. 1998; Michaud 2002; Alyokhin and Sewell 2004; Evans 2004; Sato et al. 2004; Snyder et al. 2004; Lucas et al. 2007; Pell et al. 2008; Gardiner et al. 2011; Hodek et al. 2012; Smith and Gardiner 2013; Turnipseed et al. 2014). Intraguild predation also plays a major role in preventing recolonization by native lady beetles and females avoid oviposition sites where intraguild predators are present (Ruzicka 1997; Hodek et al. 2012).

Despite documented declines in subpopulations of native species of lady beetles in Canada (e.g., Turnock et al. 2003) and the arrival and range expansion of non-native lady beetles in North America (e.g., Wheeler and Stoops 1996; Lucas et al. 2007), the links between the non-native species and causes of the declines are not clear. For example, Acorn (2007) and Harmon et al. (2007) argued that there is little direct evidence that competition or other interactions with recently arrived non-native species have caused the declines in native species. While trends are consistent with expectations, if Seven-spotted Lady Beetles and Multicolored Asian Lady Beetles negatively impact Transverse Lady Beetles through scramble competition and intraguild predation, other potential mechanisms include introduction of parasitoids or pathogens (Losey et al. 2012).

Parasites, parasitoids, pathogens and fungi:

Non-native species may also affect native lady beetles indirectly through the introduction and transmission of new natural enemies such as exotic parasites and pathogens (Bjornson 2008). These include parasitoids (i.e., braconid wasp D. coccinellae), parasitic mites (i.e., Coccipolipus hippodamiae), nematodes, protozoans, fungal pathogens (i.e., Beauveria bassiana), microsporidia (Nosematidae), and bacteria. All can negatively impact lady beetle fitness and reduce survivorship over winter (Cali and Briggs 1967; Hurst et al. 1995; Ceryngier and Hodek 1996; Barron and Wilson 1998; Webberley and Hurst 2002; Cottrell and Shapiro-Ilan 2003; Webberley et al. 2004; Bjornson 2008; Roy and Cottrell 2008; Riddick et al. 2009; Bjornson et al. 2011). Although the effect of these exotic parasites and pathogens on the Transverse Lady Beetle is uncertain, native species typically have a greater susceptibility (Cottrell and Shapiro-Ilan 2003). Obrycki (1989) reported greater susceptibility of native lady beetles to the exotic braconid wasp D. coccinellae, compared to non-native species, such as the Multicolored Asian Lady Beetle. Cottrell and Shapiro-Ilan (2003) also reported greater susceptibility of native lady beetles to an exotic fungal pathogen (Beauveria bassiana) compared to the Multicolored Asian Lady Beetle. Greater susceptibility to exotic pathogens may therefore provide an intraguild advantage to non-native lady beetles and could have been a contributing factor in declines of Transverse Lady Beetles.

Threat 9. Pollution (low impact)

9.3 Agricultural and forestry effluents

While lady beetles can be more tolerant of pesticides than their prey (Gesraha 2007), pollution via agrochemicals to reduce insect pests can impact non-target lady beetles directly through topical contact; residual contact; inhalation of volatiles; and ingestion of insecticide-contaminated prey, nectar or pollen (Smith and Krischik 1999; Youn et al. 2003; Singh et al. 2004; Moser et al. 2008; Moser and Obrycki 2009; Eisenback et al. 2010) and indirectly through eliminating their food supply (Hodek et al. 2012; Bahlai et al. 2015). Zoophytophagy, omnivorous feeding behaviour that occurs when plant material (pollen, nectar, leaf tissue) is consumed by primarily predaceous species, increases fecundity, and reduces development time (Coll 1998; Patt et al., 2003; Moser and Obrycki 2009). However, zoophytophagy can also be harmful if the plant material is chemically protected by insecticides (Moser and Obrycki 2009). Lady beetle susceptibility to insecticides varies with the species and the type of pesticide and can range from acute lethal effects to reduction in fecundity, behaviourally or reproductively by non-lethal concentrations of insecticides (Theiling and Croft 1988). Many insect predators exposed to more than one compound suffer synergistic detrimental effects, even for compounds that were equitably harmless when tested separately (Petersen 1993).

In urban and agricultural landscapes, lady beetle subpopulations may be threatened by a variety of pesticides including neonicotinoids, insect growth regulators and broad-spectrum pyrethroids, which tend to be more destructive to lady beetles than organophosphates (Kumar and Bhatt 2002; Moser and Obrycki 2009). Insect growth regulators such as buprofezen and pyriproxyfen generally lack acute toxicity to lady beetles, but may impair development and fecundity (Olszak et al. 1994). Neonicotinoids are a class of systemic pesticides that travel and accumulate throughout the plant, including pollen and nectar. While very effective against plant pests, especially aphids, these pesticides have proven to be detrimental to insects at concentrations in the parts per billion (Smith and Krischik 1999; Marletto et al. 2003). Neonicotinoids can also be applied to seeds prior to planting to protect seedlings from early-season root and leaf feeding. In one study 72% of Multicolored Asian Lady Beetle larvae exposed to seedlings treated with neonicotinoids developed neurotoxic symptoms (trembling, paralysis, and loss of coordination) from which only 7% recovered (Moser and Obrycki 2009). Therefore, the use of neonicotinoids may have negative effects on non-target species especially if zoophytophagy occurs.

Threat 7. Natural system modifications (low impact)

7.3 Other ecosystem modifications

Conversion of managed lands and farms resulting in forest regrowth, specifically in eastern ON, could potentially be a factor in the decline of the Transverse Lady Beetle and other native lady beetles (Bucknell and Pearson 2007; Harmon et al. 2007). Urban expansion and abandonment of farmland may mean less favourable foraging (Harmon et al. 2007). While these large scale changes in habitat and prey availability suggest a possible explanation, there are no data to demonstrate causality between a changing landscape and lady beetle densities (Elliott and Kieckheffer 1990; Elliott et al. 1999; Harmon et al. 2007).

Threat 2. Agriculture and aquaculture (negligible impact)

2.1 Annual and perennial non-timber crops

Habitat loss and declines in habitat quality are ongoing throughout the species’ range (Federal, Provincial and Territorial Governments of Canada 2010; Javorek and Grant 2011). Homogenization of agricultural landscapes and changing agricultural practices such as intensive reliance on fertilizers and pesticides could also contribute to local declines in native species (Wheeler and Hoebeke 1995; Bianchi et al. 2007; Evans et al. 2011). This is discussed in the pollution section (Threat 9).

Planting of genetically modified (GM) insect-resistant crops, e.g., GM corn engineered to express Bacillus thuringiensis (Bt) toxins was considered a potential risk to lady beetles because the toxin was present in pollen (Harwood et al. 2007), but not present in aphids (Hodek et al. 2012). While most studies have found no effect of Bt corn pollen consumption on fitness parameters of lady beetles (Duan et al. 2002; Lundgren and Wiedenmann 2002; Porcar et al. 2010), others have detected reduced fecundity and developmental delays (Moser et al. 2008).

Threat 1. Residential and commercial development (negligible impact)

1.1 Housing and urban areas; 1.2 commercial and industrial areas

Habitat loss and declines in habitat quality from expansion of residential and commercial developments may be contributing to local declines of this species in some parts of its range, particularly southern ON. Green areas and local gardens within smaller urbanized areas, however, may also still provide habitat for the Transverse Lady Beetle.

Number of locations

It is not possible to calculate the number of locations for this species. The term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. This species has a broad geographic range and is highly mobile, the threats to it remain unclear and variable across its range, and the number of location is not applicable.


Protection, status and ranks

Legal protection and status

There are no federal or provincial laws that protect the Transverse Lady Beetle, mitigate threats to this group of insects or protect the species’ habitat.

Non-legal status and ranks

This species has not yet been ranked globally or nationally. The conservation data centres across Canada have assigned status ranks as follows: ON: S1, YT: S4; NT: S4S5; BC: S5; AB, SK, MB: S4S5; ON: S1; QC: S4; NB, NS, PE: SH; NF: SU; NF (Labrador only): S5.

The Canada National Status Ranks (Canadian Endangered Species Conservation Council [CESCC 2015]) assessed this species in 2010 as Sensitive.

The IUCN Red list (2015): Not assessed

The species has not been reviewed or listed under the U.S. federal Endangered Species Act.

Habitat protection and ownership

Given the expansive range and broad habitat niche of the Transverse Lady Beetle across Canada, several suitable areas of habitat occur within privately owned urban and agricultural land, public land and protected areas.

The Canadian range of Transverse Lady Beetle spans numerous provincial and national parks and protected areas.


Acknowledgements and authorities contacted

The authors wish to thank Jennifer Heron for supervising this report, as well Angèle Cyr, Jenny Wu and Alain Fillion (COSEWIC Secretariat), in addition to David McCorquodale (Cape Breton University); John Acorn (University of Alberta); John Losey (Cornell University); Cory Sheffield (Royal Saskatchewan Museum); Suzanne Carrière, Danny Allaire, Nicholas Larter (Northwest Territories Government); Mary Sabine (New Brunswick Government); Barb Sharanowski (University of Manitoba); Gilles Boiteau (Agriculture Canada); Isabelle Gauthier, Nathalie Desrosiers (Ministère des Forêts, de la Faune et des Parcs); Ken Millard, Lisa Ott (Galiano Conservancy Association); Claudia Copley, Darren Copley, Heidi Gartner and Rob Cannings (Royal British Columbia Museum); Syd Cannings, Amy Ganton and Ruben Boles (Canadian Wildlife Service, Environment and Climate Change Canada); J. Grant Pryznyk (Wek’èezhìi Renewable Resources Board); Kaytlin Cooper (Gwich’in Renewable Resources Board), Gary Anweiler, Heather Leibel, Matthias Buck, Robb Bennett, Erica McClaren, Berry Wijdeven, Mark Weston, Lynn Westcott, Sandy Cessellie, Bill Ramey, Bev Ramey, Michael Dunn, Geoff Lynch, Nick Burdock, Jeevan Sandu, Sylvia Letay, Rick Howie, Lea Gelling, Kathy Coot, Tom Foot, Karen Durovich, Sara Kalnay-Watson, Al Harris, Rob Foster, Vincent Bereczki, Bruce Bennett, and the Lost Ladybug Project. Photographs of the Transverse Lady Beetle courtesy Steve Marshall.


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Biographical summary of report writers

Dr. Paul Grant is an avid entomologist who has worked with many insect groups including dragonflies, butterflies, katydids and beetles. Currently, his research focus involves insect bioacoustics. Specifically, the limitations and solutions for effective communication, predator-prey relationships, and utilizing insect calls to monitor species and habitats. Paul is also a Grasshopper Specialist Group member (GSG) for the International Union for Conservation of Nature & Species Survival Commission (IUCN / SSC) and Co-Chair for the Arthropod Species Specialist Committee (SSC) for the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).


Collections examined

Acadia University *, Wolfville, NS

Atlantic Forestry Centre, Canadian Forest Service, Natural Resources Canada, Fredericton *, NB

Atlantic Forestry Centre, Canadian Forestry Service, Natural Resources Canada, Cornerbrook Office, NF *,

Canadian National Collection of Insects, Arachnids and Nematodes, Ottawa, ON

Canadian Museum of Nature *, Ottawa, ON

Claude Chantal Collection, Québec

Collection d’insectes du Québec, Québec, QC

Collection Ouellet-Robert, Québec, QC

Great Lakes Forestry Centre *, Sault Ste. Marie, ON

Greg Pohl pers. data 2014

Insectarium de Montréal, Montréal, QC

Insectarium René-Martineau Collection, Laurentian Forestry Centre, Canadian Forest Service, Natural Resources Canada, Québec, QC*

John Acorn pers. data 2014

Lost Lady Bug Project

Musée d’Entomologie Lyman

Nova Scotia Agricultural College * (now part of Dalhousie University), Halifax, NS

Royal Alberta Museum, Edmonton, AB

Royal British Columbia Museum, Victoria, BC

Royal Ontario Museum *, Toronto, ON

Université Laval, Laval, QC

University of Alberta, Edmonton, AB

University of British Columbia, Beaty Biodiversity Museum Spencer Entomological Collection, Vancouver, BC

University of Guelph *, Guelph, ON

University of Manitoba, Winnipeg, MB

University of New Brunswick *, Fredericton, NB

* Databased by David McCorquodale (McCorquodale et al. 2011)


Appendix 1. threats assessment worksheet.

Threats assessment worksheet

Species or ecosystem scientific name:
-
Element ID
-
Elcode
-
Date:
13/02/2015
Assessor(s):
Jenny Heron (Co-chair and facilitator), Paul Grant (Co-chair and author), David McCorquodale (SSC member), John Klymko (SSC member), Syd Cannings (SSC and COSEWIC member), Shelley Pardy (COSEWIC member for NL), Nathalie Desrosiers (COSEWIC member for QC), Michael Svoboda (CWS-QC), and Angèle Cyr (COSEWIC Secretariat and comment recorder)
References:
-
Overall threat impact calculation help:
Threat impactThreat impact (descriptions)Level 1 Threat impact counts:
high range
Level 1 Threat impact counts:
low range
AVery high00
BHigh10
CMedium01
DLow22
-Calculated overall threat impact:HighMedium
Assigned overall threat impact:
BC = High - Medium
Impact adjustment reasons:
-
Overall threat comments
-
Threats assessment worksheet table.
#ThreatImpact
(calculated)
Scope
(next
10 Yrs)
Severity
(10 Yrs
or
3 Gen.)
TimingComments
1Residential and commercial developmentNegligibleNegligible (<1%)Negligible (<1%)High (Continuing)-
1.1Housing and urban areasNegligibleNegligible (<1%)Negligible (<1%)High (Continuing)Habitat loss and declines in habitat quality from expansion of residential developments may contribute to local declines of this species. However, green areas and local gardens within smaller urbanized areas may provide habitat for the Transverse Lady Beetle.
1.2Commercial and industrial areasNegligibleNegligible (<1%)Negligible (<1%)High (Continuing)Habitat loss and declines in habitat quality from expansion of commercial developments may contribute to local declines of this species.
1.3Tourism and recreation areas----Habitat loss and declines in habitat quality from recreation and tourism is minimal or potentially beneficial. Most recreation areas have open areas that provide suitable habitat for Lady Beetles, or contribute to maintaining open habitat.
2Agriculture and aquacultureD - NegligibleNegligible (<1%)Negligible (<1%)High (Continuing)-
2.1Annual and perennial non-timber cropsD - Not a ThreatSmall (1-10%)Neutral or Potential BenefitHigh (Continuing)Agricultural land and crops are beneficial for this species and its prey. However, homogenization of agricultural landscapes, and changing agricultural practices such as intensive reliance on fertilizers and pesticides contribute to local declines in native species (Wheeler and Hoebeke 1995; Bianchi et al. 2007; Evans et al. 2011). Homogenization of agricultural landscapes is discussed under other ecosystem modifications (Threat 7). Pesticides are discussed in the pollution section below (Threat 9).
2.2Wood and pulp plantationsNegligibleNegligible (<1%)Negligible (<1%)High (Continuing)Negligible. Wood and pulp plantations are typically not botanically diverse, and this may lead to less prey (aphids). In the prairies wood and pulp plantations are not important. Some areas in its range are intensively managed for pulp and paper.
2.3Livestock farming and ranchingNot a ThreatSmall (1-10%)Neutral or Potential BenefitHigh (Continuing)Transverse Lady Beetles are known to occur in heavily grazed areas in Alberta, and direct impact from grazers is unlikely. Grazing is also beneficial, and maintains open habitat.
2.4Marine and freshwater aquaculture----Not applicable.
3Energy production and mining-----
3.1Oil and gas drilling----Roads, seismic lines and other linear features create new open habitat and help with dispersal. Overall it is beneficial.
3.2Mining and quarrying----Sand quarrying can be beneficial to this species in habitat creation.
3.3Renewable energy----Wind turbines (e.g., ON): Access roads may be a potential benefit. Lady beetle mortality from wind turbines are undocumented and unlikely a threat.
4Transportation and service corridors-----
4.1Roads and railroads----Not a threat due to preference for open habitat and linear features help with dispersal.
4.2Utility and service lines----Potential benefit (see Threat 3). Pipe lines and power lines occur throughout this species range and are considered a benefit as they create new open habitat and help with dispersal.
4.3Shipping lanes----Not applicable.
4.4Flight paths----Not applicable.
5Biological resource use-----
5.1Hunting and collecting terrestrial animals----This species is not collected in the wild for biological control. Insects for biological control are reared from culture, mainly in the United States.
5.2Gathering terrestrial plants----Not applicable.
5.3Logging and wood harvesting----Not applicable. Clearcutting is beneficial for this species as it creates ideal open habitat.
5.4Fishing and harvesting aquatic resources----Not applicable.
6Human intrusions and disturbance-----
6.1Recreational activities----Not applicable. Neutral or potentially beneficial through creating high quality habitat or maintaining open habitat (e.g., recreational use of all-terrain vehicles).
6.2War, civil unrest and military exercises----Not applicable.
6.3Work and other activities----Not applicable. The number of specimens collected for research is considered to have a negligible impact on the overall population.
7Natural system modificationsLowSmall (1-10%)Slight (1-10%)High (Continuing)-
7.1Fire and fire suppression----Neutral or not a threat. Fire typically creates open habitat and allows for the succession of flowering plants which would be beneficial. Fire suppression prevents creation of open habitat. 30% of grasslands in the prairies have vanished due to fire suppression. In the Northern boreal forest, fire suppression has resulted in build of up fuel loads, creating fires that burn too hot and potentially impact succession of flowering plants.
7.2Dams and water management/use----Not applicable. Within the next 15 years a large hydro reservoir will be built in the YT. Some habitat will be lost due to flooding, but overall this is not considered an applicable threat.
7.3Other ecosystem modificationsLowSmall (1-10%)Slight (1-10%)High (Continuing)Abandonment of managed lands and farms, primarily in Eastern Canada, could potentially be a factor in the decline of the Transverse Lady Beetle. This results in less favorable foraging for the Transverse Lady Beetle, as succession occurs and ideal habitat is lost. In addition homogenization of agricultural landscapes reduces habitat quality and foraging for this species.
8Invasive and other problematic species and genesBC - High - MediumPervasive (71-100%)Serious - Moderate (11-70%)High (Continuing)-
8.1Invasive non-native/alien speciesBC - High - MediumPervasive (71-100%)Serious - Moderate (11-70%)High (Continuing)Insect generalist predators have been introduced outside of their native range inadvertently or intentionally as biocontrol agents since the late 19th century. Significant declines in geographic range and abundance of native insects are frequently due to changes in habitat or interactions with non-native species. Establishment of non-native lady beetles (e.g., Seven-spotted Lady Beetle), in North America has been implicated in an overall reduction in Transverse Lady Beetle and other native lady beetle subpopulations. Most explanations focus on direct effects through competition and intraguild predation or indirect effects through introduction of pathogens. Pathogens are potentially a large threat to this species.
8.2Problematic native species----Not applicable. No known native species that is problematic.
8.3Introduced genetic material----Not applicable.
9PollutionD - LowRestricted (11-30%)Moderate (11-30%)High (Continuing)-
9.1Household sewage and urban waste water----Not applicable.
9.2Industrial and military effluents----Not applicable.
9.3Agricultural and forestry effluentsD - LowRestricted (11-30%)Moderate (11-30%)High (Continuing)Pesticides used in agricultural areas have potential to impact lady beetles directly, and indirectly by reducing aphid densities (food source) on crops.
9.4Garbage and solid waste----Not applicable.
9.5Air-borne pollutants----Not applicable.
9.6Excess energy----Not applicable.
10Geological events-----
10.1Volcanoes----Not applicable.
10.2Earthquakes/ tsunamis----Not applicable.
10.3Avalanches/landslides----Not applicable.
11Climate change and severe weather-----
11.1Habitat shifting and alteration----Unknown. This is a widely distributed species in North America, which occurs across ecozones and habitats.
11.2Droughts----Unknown. When plants get stressed, they become more vulnerable to aphids and other insect pests, which could be a benefit.
11.3Temperature extremes----Unknown. This species occurs across a wide variety of temperature regimes in North America. However, late season frosts may affect plants, aphids and lady beetles. Some stressors increase aphid densities and others may be a detriment.
11.4Storms and flooding----Not applicable.

Classification of Threats adopted from IUCN-CMP, Salafsky et al. (2008).