Synonyms and other taxonomic changes
Speranza sulphurea (Packard, 1873)
There are 50 species of the genus listed for America north of Mexico. (1)
Rich cream-yellow with maroon brown markings, consisting of two to three wedge shaped spots along the forewing costa, prominent discal spots, and variable PM and submarginal lines. The forewing PM band is usually light and spotty, but always widens to a patch at the anal margin. Fringe entirely maroon-brown, unlike the similar M. occiduaria which has the dark forewing fringe restricted to the apex. Sexually dimorphic, females with slightly reduced wings, although not to the same extent as andersoni, simplex and occiduaria. Ferguson (1953) named the subspecies amboflava from western Canada (type locality Calgary) to describe our yellow populations, which are, according to Ferguson, quite distinct from the smaller, greyish eastern sulphurea. (AEC)
Nova Scotia west to BC, south to California and South Dakota (McGuffin 1972; Fauske 2003).
Prairie and parkland woods and shrubby habitats. (AEC)
Flies in July and August, peaking in mid to late July. (AEC)
Unknown in western North America. Larva feed on Vaccinium and Myrica gale in eastern North America (Ferguson 1953; Forbes 1948).
The life history has not been recorded in detail. Mature larvae are light green with a slightly paler head and a cream dorsal and lateral stripe (Franklin 1907, cited in McGuffin 1972). In eastern North america this is a forest species associated with blueberry (Vaccinium) and sweet gale (Myrica gale). The western race prefers drier habitats, and is not found in association with these plants. The differences in adult size, colouration and habitat preferences between eastern and western populations suggests that they may be separate species. (AEC)
Regarding sulphurea and amboflava, Ferguson states:
"Speranza sulphurea is a sexually dimorphic, eastern, bog-dwelling species, of which the male is nearly the color of Speranza argillacearia ["more nearly immaculate mouse gray"]. (MONA Fascicle 17.2, pg.82)
"Speranza amboflava is the obvious sister species of sulphurea, replacing the latter species in the West. It lacks the conspicuous sexual dimorphism of the eastern species; both sexes are bright yellow and closely resemble females of sulphurea, although usually larger." (MONA Fascicle 17.2, pg.84)
However, more current data than Ferguson (2008) does have sulphurea collected in the pacific northwest and there is a growing number of sequenced male individuals from that population that are quite yellow, and quite well marked. As more individuals of the two species are sequenced, we're finding that the external characteristics are less reliable than previously thought--or so it seems based on the genetic evidence. So distinguishing yellow individuals by photo in overlapping distribution locales may prove difficult or impossible at this time.