Art Shapiro's Butterfly Site - Euchloe

Euchloe ausonides

admin — Sun, 28 May 2006 18:09:15 +0000

Formerly common in the Central Valley, Delta, Bay Area and lower foothills, this species has suffered an unexplained crash and is teetering on the brink of regional extinction. It had been a great success story! From its biology we inferred that its native host plant was the tall mustard Guillenia (formerly Thelypodium) lasiophylla, now a rare plant in the Valley grasslands. It had successfully made the transition to naturalized annual species of Brassica and Raphanus and was doing very well through the 1980s. It had two broods a year (February-April and April-June) and the second- brood animals were large and richly-colored, the females often distinctly orange. The second brood disappeared first, as the database shows, and then the first brood followed. The Large Marble is now extinct at all my Valley sites, and the situation is the same throughout the region. We have no idea why.

The eggs are laid singly on terminal flower buds, and the larva, which is striped lengthwise in greenish-gray and yellow, feeds only on buds, flowers and fruit. It closely resembles the larvae of the Checkered and Western Whites.

In the mountains this species is single-brooded, found spottily along streamsides and in the alpine zone; its hosts there are not known. At Sierra Valley it breeds on a number of weedy Brassicaceae, including Descurainia and Sisymbrium. All the mountain populations on our transect also appear to be in decline. The population at Lang Crossing was, however, transient in any case.

Males patrol along linear habitats. Adults visit Brassicaceous flowers as well as others. Or should all these statements be in the past tense?

Euchloe hyantis "foothill"

admin — Sun, 28 May 2006 18:09:14 +0000

See discussion of the three entities in this complex under E. hyantis hyantis

Euchloe hyantis hyantis

admin — Sun, 28 May 2006 18:09:13 +0000

Three different subspecies (two of them named) occur on our transect.

The "foothill" subspecies (apparently unnamed) occurs in rocky canyons on the Sierran West slope from about 600' to about 3000'. It is rather large and the wings are more rounded than in the "montane" subspecies. Its flight is often higher off the ground. Males patrol along the bases of cliffs, often rising to the top and redescending in a repeated circuit. Local but often common, mostly on metasedimentary substrates but occasionally on serpentine. This is the entity that occurs in the Yuba, Bear, and American River canyons at lower elevations.

One brood, February-June, depending on both site and the weather of the year. The host plant is the erect, tall, usually branched lower-elevation "race" of Jewel Flower, Streptanthus tortuosus (Brassicaceae). Larvae feed primarily on buds, flowers and fruit, "stemming" the distal part of a shoot. Adults visit the flowers of the host, but also Fiddleneck, Blue Dicks, composites, Yerba Santa, Phacelia, etc.

The "montane" subspecies, which we are treating as nominate hyantis, is generally common on the Sierran West slope from about 4500' to tree-line in open, rocky habitats - never in forest. It spills over onto the East slope in montane chaparral, e.g. between Donner Summit and Truckee. It flies low near the ground. The wings are typically smaller and less rounded than in the "foothill" animals, but the "beat-flying" behavior is the same.

One brood, emerging very early - usually one of the first things flying in spring at 5000' (March-July). The usual host is the high-altitude "race" of Jewel Flower, Streptanthus tortuosus, which is low to the ground, generally quite small, bright yellow-green with the cauline leaves strongly perfoliate. One hyantis larva can consume the entire reproductive outputof a small host, rendering its fitness zero. Attacked plants are very conspicuously "stemmed." This race of Jewel Flower grows on both metasedimentary substrates (as in the South Yuba Canyon) and granodiorite ("granite") (as at Donner Summit), but not normally on volcanics.

Populations of E. hyantis in the Coast Range (usually in chaparral, often on serpentine) and on serpentine in the Sierra are phenotypically similar to hyantis hyantis. They often feed on serpentine-adapted Jewel Flower species, several of which are endemic to the Coast Range (e.g.,S. breweri). There are a few records of this species also feeding on various Arabis in our area.

"Montane" hyantis adults visit flowers aviodly, including Yerba Santa, Dogbane, composites -- and Brassicaceae, including their hosts.

The "east slope" subspecies, E. hyantis lotta, is found in sagebrush shrub-steppe and barely enters our transect area on the east side of Sierra Valley and around Beckwourth Pass. It has the dark spot at the end of the forewing discal cell large and a bit "smeary." One brood in early spring;host certainly Brassicaceous, but not determined in our area. It is not known if this entity actually breeds at our Sierra Valley site, or merely strays in.

Euchloe hyantis lotta

admin — Sun, 28 May 2006 18:09:12 +0000

Confined to sagebrush-bitterbrush shrub-steppe on the Sierran East slope. See discussion under E. hyantis hyantis, where the three entities along the transect are compared.