|scientific name Colias alexandra |
common name Alexandra's Sulphur
Gravelly and eroding prairie grasslands.
Two broods, peaking in late May to mid June and late July to mid August.
A combination of the following traits will usually distinguish this species: hindwing underside quite greenish, with no row of dark spots and an unbordered, silver discal spot; upperside bright, cold-yellow with no trace of orange. It is found only in prairie (rarely in the southern foothills) grassland habitat.
The eggs of Colorado populations are at first yellow-green, then turning pink, and are conical in shape with longitudinal ridges (Guppy & Shepard 2001). Mature larvae are black-dotted and green, with alternating dark and light longitudinal stripes (Layberry et al. 1998, Guppy & Shepard 2001). In Colorado, third instar larvae overwinter (Guppy & Shepard 2001). Pupae are yellowish-green with light markings that mimic leaf veins (Guppy & Shepard 2001).
Not of concern.
There are no larval or adult diet data available for Alberta populations. A number of legume species are known larval host plants in the US, as summarized by Guppy & Shepard (2001). They include members of the genera Astragalus, Lathyrus, Oxytropis and Thermopsis which are all legumes (Fabaceae).
This species occurs from central BC across to southern Saskatchewan, south to California and New Mexico (Opler 1999). In Alberta, it occurs chiefly along the southern reaches of the Red Deer River valley and southward. The depiction of locality records throughout the Alberta foothills in Layberry et al. (1998) is incorrect, and may be referable to C. christina; these two species were once considered to be variations of the same species.
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