J.D. Lafontaine and J.T. Troubridge. 1998. Moths and Butterflies (Lepidoptera) in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

MOTHS AND BUTTERFLIES
(LEPIDOPTERA)

J.D. Lafontaine
and
J.T. Troubridge

LEPIDOPTERA MIGRANTS/VAGRANTS

Only about 20 species of Lepidoptera occur in the Ecozone as seasonal migrants. Five of these are butterfly species (3 % of the butterfly fauna); this compares with 100 species of Lepidoptera and 30 species of butterflies (21 % of the fauna) in the Mixedwood Plains Ecozone in southeastern Canada (Lafontaine, 1996). The number of tropical and subtropical moths and butterflies that migrate northward each summer is much greater in eastern North America than in the west. The Atlantic Coast and Mississippi Valley form natural flyways for migrants, whereas the complex patterns of mountain ranges, desert areas, and diverse habitats in western United States and Canada seem to limit the northward movement of species. The most famous of the migrants is the Monarch (Danaus plexippus); the population in the Montane Cordillera Ecozone overwinters in California, whereas those that occur in central and eastern Canada overwinter in Mexico. The Painted Lady (Vanessa cardui) is another regular migrant. Three others, the Sachem (Atalopedes campestris), the American Lady (Vanessa virgieniensis), and the Variegated Fritillary (Eupoieta claudia), are infrequent migrants in the Ecozone. Another group of powerful fliers, the Sphinx Moths (Sphingidae), includes only two migrants (Agrius cingulata and Hyles lineata) in the Ecozone compared with 9 migrant species in the Mixedwood Plains Ecozone. Two other families of Lepidoptera show a fair proportion of vagrant species: the Noctuidae and Pyralidae. Among pest species of Noctuidae that migrate regularly into the Montane Cordilleran Ecozone are the Corn Earworm (Helicoverpa zea), Variegated Cutworm (Peridroma saucia), and Black Cutworm (Agrotis ipsilon) Among the Pyralidae, two pests species are migrants: the Alfalfa Webworm (Loxostege cereralis) and Beet Webworm (Loxostege sticticalis). Only a few species of microlepidoptera other than Pyralidae are migratory, the most famous one being the Diamond-back Moth (Plutella xylostella) which sometimes migrates in huge swarms numbering many millions of moths and has even reached Greenland. Some authors (e.g. Smith, 1994) believe that the spread of this species has been greatly aided by man and list it as an introduced species in British Columbia.

RECENT CHANGES IN DISTRIBUTION

Recent changes in Lepidoptera distribution involve both expanding ranges and contracting ranges. Natural changes in distribution can be difficult to detect because they tend to be slower and more subtle than the dramatic changes caused by man. Unfortunately, most expanding ranges involve introduced species and most contracting ranges relate to the destruction of natural habitats.

Introduced Species

British Columbia has a disproportionately high number of introduced species. A list of 67 exotic species in British Columbia was given by Smith (1994) and this list is discussed and expanded in appendix four, bringing the current total to 89. A significant proportion of these species were first introduced into North America in the Vancouver area, and others that were introduced eastern North America have been introduced into the west independantly from Eastern Asia, or secondarily from eastern North America, through the Vancouver area. This number is more than double the number of introduced species found in the Mixedwood Plains Ecozone. Most of the introduced Lepidoptera species in British Columbia are restricted to the Pacific Maritime Ecozone, mainly the greater Vancouver area, and have not been able to spread over the mountains into the interior. The exceptions to this generality are agricultural pests, especially those associated with fruit trees and grapes, that have been transported to into the interior, probably with nursery stock.

Native Species

Changes in distribution among native species is much more difficult to document because it requires the use of negative evidence. For example, if a species has moved into an area, or has withdrawn from an area, these can only be demonstrated if the lack of collections can be taken as valid evidence that the species is, or was, absent. Although several species of butterflies are believed to have been extirpated from the Pacific Maritime Ecozone (Guppy et al., 1994), none is known to have disappeared from the Montane Cordilleran Ecozone. One species, the Mormon Metalmark (Apodemia mormo), considered endangered in British Columbia (Guppy et al, 1994), was previously known from the Okanagan and Similkameen Valleys. It has disappeared from the Okanagan Valley, but is expanding its range in the Similkameen Valley along 50 km of roadside near the US border where its larval food plant, Snow Buckwheat (Eriogonum niveum), is spreading (Layberry et al., 1998). The Sandhill Skipper (Polites sabuleti) was first found in British Colmbia in 1975 when a number of colonies were discovered in abandoned lots in and around Penticton (Garland, 1977). The species continues to abound in these areas and has now been found elsewhere in the Okanagan as well. The fact that this species was not previously collected in the Okanagan, despite relatively heavy butterfly collecting, and the disturbed habitats that it frequents, suggests that this species may have moved into the area recently from northern Washington where it has been known to occur for many years.

ENDANGERED AND THREATENED SPECIES

Other than butterflies, most species of Lepidoptera are not well enough collected or regularly monitored in the Montane Cordillera Ecozone to determine whether or not they are endangered or threatened. Many species of moths, espcially among the microlepidoptera, have only been collected once or twice in the Ecozone, and may well turn out to quite common in the right habitat. Since so much of the original bunch-grass habitat of the Okanagan Valley has been eliminated, it is possible that some of the many moths known only from this area in Canada might be endangered but there has been so little moth study in the area that it not possible to determine this for any species. It is quite possible that some species of moths disappeared from Canada before we ever knew that they occurred here and that some species previously recorded in Canada may no longer occur. Many species occur in this type of habitat in northern Washington but are unknown in Canada. Some of these may yet be found here, others may already have been extirpated. The only moth species in the Montane Cordillera Ecozone that is either endangered or extirpated is the cutworm Copablepharon hopfingeri. This species was historically known only from a few small dune areas in Washington and one near Robson, BC. Efforts to rediscover the species at the known and other sites have been unsuccessful. In BC, the dunes at the previously known sites have been so altered that it is unlikely the species still occurs at them, although it still survives near the type locality in Washington State.

Two reports on butterflies of conservation concern in British Columbia (Guppy and Shepard, 1994 and Guppy et al., 1994) identified 52 species and subspecies of concern in British Columbia. Of these, 17 occur in the Montane Cordillera Ecozone. One (Egleis Fritillary, Speyeria egleis) was reported from Canada in error (Layberry et al., 1998) and a second, the Viceroy (Limenitis archippus) has been extirpated from British Columbia. The Viceroy is primarily a butterfly of eastern United States and southern Canada east of the Rocky Mountains but a thriving population existed in central Washington and the southern interior of British Columbia until 1916, but the population declined rapidly between 1916 and 1920 with only occasional reports of the species in BC until 1930 and in Washington until 1940 (Guppy et al., 1994). The reason for the decline of the western population of the Viceroy is unknown since its habitat, roadside and streamside willow and poplar areas are abundant. Of the 15 species of concern remaining, four are classified as “endangered,” two as “threatened,” six as “vulnerable,” and three as unknown. The four endangered species are: Mormon Metalmark (Apodemia mormo), Behr’s Hairstreak (Satyrium behrii), Sooty Hairstreak (Satyrium fuliginosum), and Grey Copper (Lycaena dione). The Mormon Metalmark, known at present only from the Similkameen Valley and discussed above under species with expanding ranges, should probably now be considered as vulnerable rather than endangered but the status of the species needs to be monitored. Behr’s Hairstreak is known only from the southern Okanagan Valley where it is closely associated with remaining stands of its larval host plant Antelope Brush (Purshia tridentata). Sooty Hairstreak is known from the Similkameen Valley, Anarchist Mountain in the southern Okanagan, and Waterton National Park in southwestern Alberta; it occurs on dry brushy slopes where lupines, the larval host plant, occurs. The Grey Copper is primarily a Great Plains species occurring from western Ontario to western Alberta with a single colony known in British Columbia at Elizabeth Lake near Cranbrook. The larva feeds on Dock (Rumex spp.). The two “threatened” species are the Sonoran Skipper (Polites sonora), restricted to the Similkameen Valley, and the California Hairstreak (Satyrium californicum), which occurs mainly in the Similkameen and Okanagan Valleys. The six "vulnerable" species are: Nevada Skipper (Hesperia nevada, Similkameen and Okanagan Valleys), Indra Swallowtail (Papilio indra, Manning Provincial Park near Allison Pass), Lilac-bordered Copper (Lycaena nivalis, Okanagan Valley), Western Green Hairstreak (Callophrys affinis, Okanagan Valley), Eastern Tailed Blue (Everes comyntas, south-eastern Kootnays), and Gillette's Checkerspot (Euphydryas gillettii, East Kootnays). Of these the Eastern Tailed Blue tends to be sporatic and invasive at the northern edge of its range, being common only in southern Ontario, so its continued existence in BC needs to be monitored. Finally three species are listed by Guppy et al. (1994) as “unknown” (Alberta Fritillary, Boloria alberta, Magdalena Alpine, Erebia magdalena, and White-veined Arctic, Oeneis bore). All three belong to the group of species associated with dry alpine tundra in western Alberta and have only rarely been recorded in the Montane Cordillera Ecozone in British Columbia. The Alberta Fritillary has an extremely small range in southwestern Alberta with two locations in adjacent BC. The White-veined Arctic is widespread in northern Canada and northern BC with its range extending southward in the Rocky Mountains to southwestern Alberta and one location in adjacent BC. Magdalena Alpine occurs locally in the Rocky Mountain region of the United States from Montana to New Mexico; in Canada it has been recorded only at four locations, two in the Wilmore Wilderness Area in Alberta, one near McBride and one in Stone Mountain Provincial Park in British Columbia. The remote nature of the habitat of these three species in the Ecozone is the reason for the “unknown” status, but known colonies should be monitored and additional colonies reported.

It is clear that the most critical areas in the Montane Cordillera Ecozone, in terms of habitat frailty, habitat loss, and threatened and endangered species are the Okanagan and Similkameen Valleys. This is obvious from the butterflies and we can only speculate that the same would be true of the moths, which outnumber butterflies in diversity by a 10:1 ratio in the Ecozone, and probably outnumber them by 20:1 according to the expected moth/butterfly ratio given by Lafontaine and Wood (1997).