Variable Checkerspot (Euphydryas chalcedona) (Doubleday, 1847)
Diagnosis: This is an extremely variable butterfly with a characteristic checkerspot pattern: black banded by orange and white spots. The underside pattern is similar but lighter in appearance. The forewing is pointed, less prominently in the female than in the male. Wingspan: 30 to 56 mm.
Subspecies: There are more than 30 subspecies currently recognized, of which three occur in Canada. Subspecies perdiccas formerly occurred on southern Vancouver Island; the orange-red spots on the upper surface are larger than in most other subspecies. Subspecies paradoxa occurs in the Coast Range west of the Fraser River Valley; it closely resembles subspecies anicia, but genitalia structure associates it with the chalcedona subspecies group (see Remarks below). Most populations in Canada are subspecies anicia, which was described from Banff, Alberta. Populations from northwestern British Columbia and Yukon have been called subspecies helvia, but these are so similar to anicia, that we include helvia within subspecies anicia. The populations from Cypress Hills, Saskatchewan, and Riding Mountain, Manitoba, are slightly atypical for subspecies anicia, but have not been studied in sufficient detail for a subspecies name to have been proposed.
Range: The Variable Checkerspot is widespread in the western mountains from Mexico to Alaska. It is most common in the Rocky Mountains of Alberta and British Columbia as far west as the Fraser River, and extends northward into Yukon and Alaska. Its occurrence west of the Fraser River is more sporadic and it has been extirpated from Vancouver Island. There are isolated colonies in the Cypress Hills of Alberta and Saskatchewan and in the Riding Mountains of Manitoba.
Similar Species: In most of its range chalcedona is likely to be confused only with Edith's Checkerspot (editha), which overlaps its range broadly. It can be distinguished from editha by its generally larger size, more pointed forewing apex in males, and the pattern on the underside of the hindwing. In chalcedona the middle of the three bands of yellow spots is entirely yellow and separated from the red band beside it on the outside by a thick black line. In editha the outer third of the yellow band is red so that the black line appears to divide the red band into two separate bands. [compare images]
Early Stages: The larvae of this species are highly variable in colour. They can be dull white covered with bristly black tubercles, black speckled in white and covered with orange tubercles, or black with white hairs and with orange spots at the base of the black tubercles. The foodplants used by different subspecies and different populations within subspecies are not well known. Known foodplants are snowberry (Symphoricarpos spp.), beardtongue (Penstemon spp.), Indian paintbrush (Castilleja spp.), and plantain (Plantago spp.).
Abundance: Subspecies perdiccas was historically known from just two areas of southern Vancouver Island, but these populations are now believed to be extirpated. Subspecies paradoxa occurs in isolated colonies west of the Fraser River Valley and can be found in fair abundance within a colony. Subspecies anicia is widespread but local in most of its range. It is common in the Cypress Hills (Hooper, 1973), but only a single specimen taken in 1933 is known from Riding Mountain National Park in Manitoba (Klassen et al., 1989).
Flight Season: West of the Fraser River, subspecies perdiccas and paradoxa fly in May and June at elevations up to 1000 metres; subalpine populations of paradoxa fly in late June and July at elevations above 2000 metres. To the east of the Fraser River subspecies anicia flies from late June to early August.
Habits: Euphydryas chadcedona flies in streamsides, meadows, and forest clearings and on scree slopes in alpine areas.
Remarks: The Variable Checkerspot is a complex assemblage of populations that have differentiated from each other to varying degrees and, like some other butterfly species, falls into a grey area between being distinct species and being interbreeding populations of a single species. The populations can be arranged in two groups based on structural differences in the male genitalia. In the chalcedona group of populations there is a long curved spine at the end of the male valve and a much shorter one (about 1/4 as long) at the base of the spine. In the anicia group of populations this basal spine is about 1/2 to 2/3 as long as the main spine. The genitalia of specimens from Vancouver Island and the Coast Range (subspecies perdiccas and paradoxa) are typical of the chalcedona group, while those of specimens from most of British Columbia and Alberta are typical of the anicia group. In specimens from the east slopes of the Coast Range west of the Fraser River, the spine is intermediate in length between the paradoxa and anicia type of genitalia and cannot be said to be one subspecies or the other. This phenomenon is typical of subspecies and indeed the chaicedona and anicia groups act like subspecies in British Columbia. While paradoxa and anicia form hybrid populations in southern British Columbia, it appears that it is only the alpine populations of paradoxa, which fly in July, that are hybridizing with anicia because the lower-elevation populations of paradoxa fly in late May and early June. The fractured ranges of the "Anicia" and "Chalcedon" Checkerspots, and the tendency of populations to inbreed and differentiate, have resulted in a situation in between species and subspecies definitions. We treat the chalcedona and anicia groups of populations as a singlespecies because of the areas in intergradation in most places where the ranges of the two come together.
© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.
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