The upperside of the wings of the male Western Spring Azure are a uniform violet blue with a narrow white margin and no orange or dark areas on either wing. The underside of the wings is a dirty chalk white, with the pattern of dark spots varying from mostly inconspicuous to very contrasting. Every population has a variable pattern on the underside of the wings. The female is similar to the male except that the dorsal forewings have wide black margins and the dorsal hindwings have a row of black marginal spots. The blue is much reduced, but is violet blue.
The literature on this species complex is very confusing, but apparently the immature stages of the Western Spring Azure have not been described except for last instar larvae (Ballmer and Pratt 1989). The ground colour of the mature larva can be white, pale pink, or pale green. Lateral lines or chevrons are absent, but there is a conspicuous transverse bar on the first abdominal segment.
Populations in BC are the nominate subspecies, C.e. echo (W.H. Edwards, 1864) (TL: San Francisco, CA) (= nigrescens Fletcher, 1903; TL: Kaslo, BC).
At the time the genus Celastrina was named, the name celastrina was used for holly, the larval foodplant of the type species for this butterfly genus (Emmet 1991). The common name "spring azures" reflects the early spring flight period and the azure (blue) wing colour of males of this genus. The name was first used by Gosse (1840) for what is now subspecies lucia of the Boreal Spring Azure.
The genus Celastrina differs from all other blues in the structure of the male genitalia. The labides and vinculum are fused and developed into a broad plate extending to articulate with the valves. The eyes are hairy. Spring azures are the first blues to emerge from the pupa in the spring and are a sure sign that spring has arrived in the northern hemisphere. The genus is Holarctic, with one species across most of Europe and Russia and several in northeastern China and adjacent areas (Eliot and Kawazoe 1983). Until very recently all North American populations were regarded as one species, but Opler and Krizek (1984) recognize three, two of which are found in eastern deciduous forest habitat. Pratt et al. (1994) further defined overlapping subspecies and overlapping races of the three species but did not recognize any additional species. Several North American authors have split off the widely distributed Nearctic species Cladon from the Palearctic species C. argiolus, but the only study to look at the genus as a whole treats argiolus and ladon as one Holarctic species (Eliot and Kawazoe 1983). Observations in BC show that the two "subspecies" of ladon occur together and must be regarded as separate species. The southern C. echo is closer in appearance to C. argiolus from the Palearctic. C. ladon is therefore kept as a separate Nearctic species. Recent unpublished DNA analysis of Pratt and Wright (in prep.) support this split into two species. Thus there are four species in North America and many more in the Palearctic.
The Western Spring Azure has two generations per year. The first flies from early April to early June and is abundant. The males congregate at mud puddles. There is a partial second generation in the warmer parts of southern BC, including southeastern Vancouver Island, near Hope, and the southern part of the Southern Interior. In California Comstock (1927) listed Ceanothus sp. as a larval foodplant. Ceanothus has been confirmed in the BC Southern Interior (FIS). On southeastern Vancouver Island, both Guppy (1954) and Hardy (GAH) have reared the Spring Azure on Holodiscus discolor. Hardy confined a female that had been walking on an inflorescence of H. discolor. It laid eggs on the inflorescence on 22-24 May; the eggs were a white, flattened sphere. The mature larvae had a black head with either an all green or purplish dorsal and green ventral body. Pupation occurred on 20-23 June. Regrettably Hardy did not record when the adults emerged.
Shepard observed adults of the Western Spring Azure in numbers along a long natural hedge of Spiraea douglasii at the back of sand dunes on Vancouver Island, but no oviposition was observed. This plant is found throughout the range of the species in BC and is likely a foodplant. In Colorado Scott (1992) found that adults with a wing pattern similar to that of BC populations oviposited primarily on Jamesia americana, a plant not found in our area. He also noted occasional oviposition on Prunus sp., and mentioned that that plant should be investigated for BC. Guppy (1954) found that the larvae fed exclusively on flowers. The larvae must pupate before winter since newly emerged adults are present in the earliest spring.
The Western Spring Azure is found throughout the southern fifth of BC, in riparian situations and along the edges of open meadows in most of southern BC. On southeastern Vancouver Island, it is also found associated with shrubs just at the back of stabilized sand dunes.
The Western Spring Azure is found from southern BC south to the tip of Baja California and south through the Rockies to northern MEX.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2020-05-28 6:16:01 PM]
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