Art Shapiro's Butterfly Site - Colias

Colias alexandra

admin — Sun, 28 May 2006 18:09:27 +0000

An uncommon grassland and shrub-steppe species on the Sierran east slope only, often seen near vernal pools. It is only accidental in Alfalfa fields and unlikely to stand out among swarms of the two Alfalfa-feeding Colias there; on theother hand, it is likely to be the only Colias flying through sagebrush and bitterbrush at, say, Beckwourth Pass. Pale females are extremely rare. The underside of the hindwing is uniform grayuish-green, and the silver discal spot has only one (purple) rim. On our transect only at Sierra Valley, and never common.

One brood in early summer, occasionally flying as late as September.Host plants species of Astragalus (locoweed) and possibly Trifolium macrocephalum. Adults visit Thistles, Alfalfa, Mule's-Ears and other flowers.

This species never hybridizes with other Sulphurs in our area.

Colias eurytheme

admin — Sun, 28 May 2006 18:09:26 +0000

Ubiquitous except in closed-canopy forest; one of our commonest butterflies, often reaching very high densities in alfalfa fields in midsummer to autumn and becoming conspicuous at that time; when the alfalfa is cut may emigrate en masse, even flooding into cities. This is also our most variable butterfly, seasonally and individually. Cold-season specimens are small, very heavily infuscated on the ventral hindwing, with reduced black borders above, increased basal black above on all wings, and the orange pigment concentrated into discal patches on a bright-yellow ground. (This is quite different from the even orange-yellow of hybrids with the Yellow Sulphur, q.v.). Summer animals are large and bright, much more orange, with broad black borders and few if any black scales on the hindwing beneath. Summer males have much more "high-angled" (triangular) forewings than cold-season ones, reflecting a different style of flight. Many females - up to 50% - have the ground color white. A very rare mutant ("blonde") produces whitish butterflies in both sexes, with a creamy look. In autumn intergrades between orange and white females occur.

The red eggs are laid singly. The larva is basically green with a white-and-pink line on each side, but may have very variable black markings as well. The pupa is apple-green with rosy highlights.

Although it is a significant Alfalfa pest, this butterfly overwinters as a larva almost entirely in annual vetch at low altitudes, and colonizes Alfalfa only as the vetch senesces in May-June. Aside from Alfalfa and annual vetches, it also breeds on a variety of Clovers and Sweet Clovers and occasionally on Lupines. It seems certain that the planting of Alfalfa has greatly increased its range and abundance. There are multiple broods, essentially all year at sea level. At higher elevations overwintering may be more problematic, though it definitely occurs some years even at Donner. The high Sierra is colonized annually in late May or June by second-brood flyups from lower elevations. Often the winter-form butterflies from overwintered larvae emerge at Donner after the big, richly-colored summer immigrants arrive! This species apparently overwinters every year at Sierraville, but in some years much better than others.

Males patrol host plants and often mate with just-emerged (teneral) females. The often-observed rising, spiraling flight involving a male and a female is not a nuptial dance but a rejection ploy by the female, which will suddenly pull out of the spiral and drop to ground level. Teneral mating, as well as very high densities in agricultural populations, favors hybridization between this species and the Yellow Sulphur where they are sympatric - east of the Sierran crest only. Bright yellow specimens occasionally taken in the Sacramento Valley are apparently pigmentary mutants of local origin, and do not reflect a history of hybridization.

The Alfalfa Butterfly often continues emerging in the mountains until killing frost - even into early winter. A few adults in the Central Valley may remain aluive until early January, and in droughty years there is effectively no winter hiatus in the flight.

Colias philodice (eriphyle)

admin — Sun, 28 May 2006 18:09:25 +0000

The Yellow Sulphur of the West is different in many ways from the Eastern one and may be its own species (eriphyle). Both, however, hybridize readily with C. eurytheme where they co-occur, almost always in alfalfa fields. Our Yellow Sulphur occurs only East of the Sierran crest and is only a rare stray at Donner. But it is a permanent resident in Sierra Valley and other irrigated alfalfa-growing areas (e.g., Honey Lake to the north and Carson Valley to the south, and eastward across the Great Basin). It strays only infrequently to open wildlands. The spring brood is very small, with narrow black borders and intense infuscation on the ventral hindwing. White females cannot always be told from C. eurytheme. Hybrids have very even, intermediate coloration (as contrasted with cold-weather forms of eurytheme, in which the orange contracts to distinct patches). Hybrids occasionally exceed 10% of the population.

Three broods at Sierraville, March to October (occasionally November). Cold-weather animals hug the south or SW-facing sides of hills; the males fly very low and directly. In summer, males patrol just over the top of the alfalfa and often mate with teneral females. Both sexes visit Alfalfa flowers freely, but also Composites of various kinds (including Rabbitbrush) and others.

Bright yellow individuals are occasionally taken in Orange Sulphur populations west of the crest, including the Central Valley. These appear to be mutant individuals of local origin.