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COSEWIC Assessment and Status Report on the White Flower Moth (Schinia bimatris) in Canada

Biology

General

Very little is known about the biology of the White Flower Moth. Adults are nocturnal and have been collected using ultraviolet light. Diurnal flight activity has also been observed in a Mississippi population where adults were quite common (R.L. Brown, pers. com.). Diurnal activity may by a response to higher population densities; this activity pattern also occurs in Schinia meadii, with adults active both in late afternoon and at night (C. Schmidt, unpubl. data).

The life cycle of S. bimatris is undoubtedly like that of all other Lepidoptera, consisting of complete metamorphosis. Larvae hatch from eggs, feed on plants, and molt several times before pupating. Adults emerge from the pupae. Although the larval food plants are unknown, most members of the genus. Schinia are known to feed on one or a few closely related host plant species (Hardwick 1996). Flower moth larvae generally feed specifically on the flowers and developing seeds of the host plant (Hardwick 1996). Adult flower moths are short-lived, and reared adults usually do not live longer than seven days (Hardwick 1996).

Reproduction

There are no data specific to S. bimatris. In general, flower moths mate during the adult flight period. Manitoba collection records indicate the flight period for S. bimatris is during the second and third weeks of July (Appendix 1). Female flower moths generally extend their ovipositor into the florets of the larval food plant to place the eggs. Because Schinia species lay eggs that are relatively large compared to their body size (Hardwick 1996), the number of eggs produced is likely lower than in other owlet moths. The reported maximum number of eggs laid by female Schinia varies from 89 in S. indiana to 356 in S. sueta (Hardwick 1958). The eggs hatch after several days. The young larvae feed within the flower heads on flower parts and on developing seeds. They grow relatively quickly, completing their development in two to four weeks (Hardwick 1996). Many flower moth species overwinter as pupae, with adult emergence timed to correspond with flowering of the host plant. All flower moths, so far as is known, pupate at or below the surface of the soil (Hardwick 1996).

Survival

There are no data specific to S. bimatris. Lepidoptera generally suffer high mortality during the larval stage as a result of predation by birds, predatory invertebrates, parasitic flies and wasps, and infection by fungal, bacterial and viral pathogens. Concealment in flower heads during feeding may be a predator/parasitoid avoidance strategy in flower moths (Hardwick 1996). Flower moths are unusual in that larvae in many species succumb to cannibalism, both from the larvae of conspecifics and of other flower moth species inhabiting the same flower head (Hardwick 1996).

Physiology

No data are available.

Movements/dispersal

There are no data available for S. bimatris. Most Schinia species are strong fliers and have a rapid, buzzing flight (C. Schmidt, unpubl. data). The ability for strong flight would facilitate colonization of host plant patches separated by unsuitable habitat. Although Schinia species may have the ability for dispersal, many species exhibit high site and hostplant fidelity and are rarely observed away from the immediate vicinity of hostplants (Hardwick 1996, Swengel and Swengel 1999).

Nutrition and interspecific interactions

The larval host plant of S. bimatris is currently not known. The moth occurs in association with a white evening primrose in the Spirit Dunes (J. Troubridge, pers. com. 2004), likely Oenothera nuttallii Sweet. This evening primrose is likely a candidate host plant because it blooms during the flight period of S. bimatris and the flowers match the colour of S. bimatris adults. Synchrony of flight with flowering as well as cryptic colouration often occur in flower moths because the adults rest on host flowers during the day (Hardwick 1996). Evening primrose species are also known to be hosts for several other flower moths (Hardwick 1996, C. Harp, pers. com. 2003). A search of about 200 Oenothera spp. flowers at the Spirit Dunes in 2004 did not reveal any S. bimatris, but the summer was unUsually cold and wet so population density may have been below detectable levels.

Should O. nuttallii prove to be the larval host plant, its distribution is not likely to limit that of S. bimatris. Oenothera nuttallii is distributed across the southern Canadian prairies and occurs south to Colorado, Wisconsin and Nebraska (Scoggan 1979). Southern U.S. populations of S. bimatris may feed on other Oenothera species.

Behaviour/adaptability

No data are available.