Art Shapiro's Butterfly Site - Pontia

Pontia beckerii

admin — Sun, 28 May 2006 18:07:49 +0000

A characteristic species of the East slope and Great Basin, sporadically breeding at Donner Pass but not persistent and not descending the West slope. Its green underside mottling is distinctive and unique in our fauna. The early-spring brood is small and very intensely-colored, with the underside mottling dark blackish-green. It flies slightly later than the Western White in most places.

Males fly along linear habitats such as roadsides. Both sexes are often seen in alfalfa fields. There are multiple broods (generally 3 at Sierra Valley) with the species flying from March-April to (usually) October. The larval host plants at our sites are weedy Brassicaceae-usually Tumble Mustard (Sisymbrium altissimum); the larvae feed primarily on the green fruit. In the Nevada desert they often feed on Prince's Plume (Stanleya pinnata).

Both sexes visit Brassicaceous flowers but also those of Alfalfa, Rabbitbrush, Goldenrod, Aster and a variety of other things. It is not uncommon to encounter this species flying through sagebrush-bitterbrush shrub-steppe far from any flowers at all.

Pontia occidentalis

admin — Sun, 28 May 2006 18:07:48 +0000

Very similar to the Checkered White, which it largely replaces at higher elevations. Our Western White is probably conspecific with the Old World Pontia callidice, and alpine or early-season specimens of ours are indistinguishable from the Himalayan taxon P. c. kalora.

The Western White is a great hilltopper, often flying in clouds around rocky balds above tree-line. But it is also at homein disturbed roadside habitats and in weedy pasture or irrigated alfalfa, as at Sierra Valley. Both sexes are extremely variable, individually and seasonally. At 9000' there is only one local brood, consisting of the extremely dark-veined phenotype "calyce," which also occurs in the first (late winter) brood at Sierra Valley, often flying in March. September-November specimens are transitional to it. To make matters more complicated, up to about 1% of specimens may be hybrids with the Checkered White where the two co-occur.

Neither species is a permanent resident at Lang Crossing, but both colonize there on a temporary basis. Occidentalis appears to be permanent at Donner, Castle and Sierra Valley. It has been recorded three times on the floor of the Sacramento Valley, all in mid-October. Two of these were at our Rancho Cordova site (in different years!). Downslope dispersal is much less often documented than the reverse, so these cases are especially interesting.

Documented host plants at our sites include Lepidium virginicum var. pubescens, L. perfoliatum, L. campestre, Cardaria pubescens, Sisymbrium altissimum and Descurainia sophia (all Brassicaceae). In addition to Brassicaceae, adults nectar at a great variety of Composites (they are regulars at Rabbitbrush and Aster) and Alfalfa, among others. The flight season in Sierra Valley is March through October, with about four broods; at Donner, June-October; on Castle Peak June-September, prolonged by altitudinal dispersal of hilltoppers not hatched locally. This species is sometimes extremely abundant, particularly in Sierra Valley.

Pontia protodice

admin — Sun, 28 May 2006 18:07:47 +0000

In the 1970s this species was often abundant at low elevation along the transect, overwintering only locally and sporadically-mostly on dredge tailings along the American River. It has since become much rarer and in most years is seen only in September and October. At Sierra Valley it overwinters unpredictably but colonizes each year from the desert in May or June, and usually becomes common by late summer. It has been recorded at all sites but is not a permanent resident at any of them at this time!

A highly vagile species, the Checkered White breeds on a great variety of Brassicaceous plants, preferring smaller and unsucculent species such as Peppergrasses (Lepidium, but L. latifolium is unpreferred), Tumble Mustard (Sisymbrium altissimum), and the short-lived perennial Hirschfeldia incana (formerly called Brassica geniculata). The eggs are orange, laid conspicuously near the top of the plant, and the larvae, which are striped lengthwise in whitish yellow and greenish gray, feed primarily on buds, flowers and fruit. However, eggs are also often laid on small rosettes, especially if the larger plants in the area are senescent. This is overwhelmingly a species of grassland and steppe and occurs in wooded areas only along roadsides.

The first brood (which may emerge as early as January at sea level, to March at Sierra Valley) is very distinctive; the butterflies are small, lustrous white above with (usually) reduced black pattern but very heavy black basal scaling, and very heavy black scaling along the veins on the ventral hindwing. This ventral vein-scaling is less greenish than in the Western White. Summer males are often immaculate or nearly so beneath, while females have at most yellow vein-scaling. Intermediates are sometimes seen in May and again in September-October. This species often remains on the wing until the bitter end of the season.

Adults visit flowers of Mustards, Composites, Legumes and almost anything else; they are often abundant in irrigated alfalfa and visit its flowers freely. Males patrol in host-plant areas and often mate with teneral females. Hybrids with P. occidentalis apparently occur, but at very low frequency; in areas of sympatry up to 1-2% of individuals may be undeterminable by wing pattern.

Pontia sisymbrii

admin — Sun, 28 May 2006 18:07:46 +0000

Always single-brooded early in the season, this is a species of rocky, unforested sites including serpentine barrens and the alpine zone. It also occurs on lava flows in Sierra Valley, straying to adjacent roadsides and alfalfa fields. The interrupted vein-lines on the underside of the hindwing are diagnostic, as is the dumbbell-shaped black spot at the end of the forewing cell. Many females are distinctly pale yellow. Higher-altitude specimens average slightly smaller, with crisper and blacker markings than foothill ones. A very infrequent stray to the Sacramento Valley.

Males patrol rocky ridges and canyon walls, and hilltop. Both sexes visit a variety of early-season flowers. The single brood flies March-May, but June-early August above tree line. Hosts are native Brassicaceae, such as species of Streptanthus (Jewel Flower) and Arabis, but at Sierra Valley also uses introduced Tansy Mustard (Descurainia sophia). I have never found it on Sisymbrium, the plant for which it is named! The eggs are red and have been demonstrated experimentally to deter oviposition by subsequent females. The mature larva is apparently a mimic of the Monarch larva. It is very conspicuous and makes no effort at concealment. The pupa is dark, obscure, usually attached to a rock, and may not hatch for up to 4-5 years.