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COSEWIC assessment and update status report on the mormon metalmark in Canada

Name and classification 

The Mormon Metalmark, Apodemia mormo (C. & R. Felder, 1859), is the only species in the family Riodinidae that occurs in Canada.  The family includes five subfamilies with about 1300 species worldwide, of which about 1200 are neotropical. 

Apodemia is a genus of about twelve species belonging to the tribe Emesini, a polyphyletic group of unresolved affinities within the subfamily Riodininae. The Emesini includes all riodinid butterflies with four radial veins, and contains over one hundred species comprising thirteen genera (DeVries 1997).  The taxonomy of the Mormon Metalmark is in flux.  Apodemia mormo, sensu lato, currently includes twenty named subspecies, of which all but four are found in California (Scott 1986, Emmel and Emmel 1998, Emmel et al 1998).  Opler (1999) divides this species complex into four species.  The Canadian populations are thought by most authors to belong to the nominate subspecies A. m. mormo (eg, Layberry et al 1998, Opler 1999, Pyle 2002). Scott (1986) considered the Saskachewan population to be A. m. mejicanus Behr.  In a more recent paper, Scott and Fisher (1998) identified a subspecies from south-central Colorado east of the continental divide as A. m. pueblo Scott, but did not reassess the Saskatchewan population The Saskatchewan population lacks the orange markings on the hindwing that are characteristic of A. m. mejicanus and A. m. pueblo, and superficially resembles those Mormon Metalmarks from British Columbia (R. Hooper pers. comm.).  Until there has been a detailed comparison of the Canadian disjuncts with those in regions further south, it seems premature to assign them to a described subspecies.

Description 

The following description applies to the nominate subspecies A. m. mormo and appears to be generally consistent with the appearance of specimens from both British Columbia and Saskatchewan.  Detailed examination of the nominate subspecies in comparison to those from the Canadian populations has not been undertaken to my knowledge.  Such a study may well reveal important differences between these populations.

Apodemia m. mormo is a small butterfly with a wingspan of 25-35 mm (Figs.1 and 2).  The sexes are similar, but males are smaller, and the forelegs are reduced and not used for walking.  Females have three pairs of functional walking legs.  The forewing costa has very little curvature.  Both wings have white checks and spots throughout the upper and lower surfaces.  The ground colour is generally dark brown above, and gray ventrally.  The ground colour of the anterior half of the basal two thirds of the forewings is red-brown on both dorsal and ventral wing surfaces (Layberry et al 1998).  The body colour is dark gray with inconspicuous, diffuse, white highlights on the abdominal segments. The eyes are green, and the antennae have strong black and white bands.

Figure 1.  British Columbia– Apodemia mormo perching on Erigonum niveum.  Photo by: D. St. John.

Figure 1.  British Columbia– Apodemia mormo perching on Erigonum niveum.  Photo by: D. St. John.

Figure 2.  Saskatchewan– Apodemia mormo perching on Erigonum pauciflorum.  Photo by: J. Pepper.

Figure 2.  Saskatchewan– Apodemia mormo perching on Erigonum pauciflorum.  Photo by: J. Pepper.

Eggs are flattened spheres, pink turning purple, laid in small groups of 2-4 on the larval hostplant (Scott 1986, Pyle 2002).  Scott (1986) describes  the larvae as “dark violet (lighter beneath), with six rows of clustered cactus-like spines, the dorsal rows black at their bases, the lateral rows ochre.”

The pupa is hairy in part, mottled brown, and is primarily found in the litter at the base of the hostplant (Scott 1986, Pyle 2002).  Colour photographs of the larva and pupa can be found in Butterflies of British Columbia (Guppy and Shepard 2001).

Nationally significant populations

The Saskatchewan and British Columbia colonies of the Mormon Metalmark butterfly should be considered as distinct, nationally significant populations.  The adults of the two populations are similar in appearance, but have not been studied in detail, nor have they been examined to determine the degree of genetic distinctiveness. 

The two populations are disjunct from each other, and from the main metalmark populations to the south.  They occupy different National Ecological Areas, the Southern Mountain Area in the case of the British Columbia population, and the Prairie Area in the case of the Saskatchewan population.  The population in British Columbia uses a different hostplant, Eriogonum niveum, than the Saskatchewan population, which uses Eriogonum pauciflorum.