Art Shapiro's Butterfly Site - Plebejus

Plebejus acmon

admin — Sun, 28 May 2006 18:08:02 +0000

This species has been found at all sites on the transect, though it is not certain that it overwinters at Donner (some years) or Castle Peak (at all). It is weedy and highly dispersive. Although some of its host plants (Deer Weed, Lotus scoparius; Wild Buckwheats, especially the Eriogonum nudum group) are perennial and allow it to have >1 generation in the same place, many (annual species of Lotus, especially L. purshianus; Polygonum aviculare group) are ephemeral and do not. It thus has to be constantly on the move, looking for hosts. The seemingly odd coupling of Polygonaceous and Fabaceous hosts is repeated in other Lycaenids and suggests an unexplored chemical commonality between the plants. The Acmon Blue is ant-associated and the larvae are often kept in the ant nest when not feeding. In return for protection, they provide honeydew.

The first (early spring) brood of Acmon is very richly colored, especially the female, which may be mostly dazzling blue above with a strongly-contrasting row of red lunules (sometimes fused into a band). Summer animals are duller, often quite small, and females are usually black above. In autumn intermediates occur; the male hindwing lunules tend to become pink and may disappear altogether above. This is a multiple-brooded species, typically flying all season (February-November near sea level, June-October in the high country); it is usually one of the last species flying at Donner Pass. At low elevations its abundance typically peaks in September-October, when it may swarm over Coyotebrush (Baccharis) flowers. When it breeds on Lotus purshianus in the beds of dry streams, the overwintering immatures may be washed away. In such cases it may not be seen locally until the second brood recolonizes in June.

The typical habitat for Acmon, be it at Suisun or Donner, is a roadside with scattered weeds and a fair bit of bare soil. It does not generally breed in shaded habitats. I have, however, found it breeding on Lotus oblongifolius along a stream in mesic-montane conditions -- showing just how adaptable it can be! At various locations it visits a vast array of flowers, from Heliotrope to Rabbitbrush.

Plebejus icarioides

admin — Sun, 28 May 2006 18:08:01 +0000

Found at all of our sites except in the Sacramento Valley and Suisun. As recently as the 1970s it still had a presence in the Valley on Lupinus formosus, but seems to be gone now. An extremely variable species with several distinctive subspecies in the Bay Area. The Sierra Valley population frequently has the spot-pattern on the hindwing beneath "blind" or nearly so (white dots without or with only very reduced black centers, on an ashen ground). Similar specimens occur occasionally on Castle Peak. Males are avid puddlers and may be quite abundant. A curious fact is that when several species of Blues are at the same puddle, they inevitably segregate by species. Boisduval's Blue routinely flies with the Silvery Blue and with the much rarer Arrowhead Blue, all of which breed on perennial lupines; telling them apart on the wing is an acquired skill.

One brood, April-June at Gates Canyon, June-August (rarely later) at higher elevations. Host plants many species of perennial lupines, the preferred species varying by locality. Adults visit a great variety of flowers, including Pink Pussy Paws, Wild Buckwheats, Composites, etc. In Sierra Valley they can often be found with the host plant far out in sagebrush steppe, where nothing (or nothing but lupine, which they do not use as a nectar source) seems to be in bloom.

Plebejus lupini

admin — Sun, 28 May 2006 18:08:00 +0000

The name is a misnomer, since this butterfly always breeds on Wild Buckwheats (Eriogonum, family Polygonaceae) and has nothing to do with lupines. However, under the International Code of Zoological Nomenclature, there's nothing one can do about that! The butterfly is very similar to the Acmon Blue, but unlike it, is always single-brooded. Although there are a few lower-elevation colonies in the Sierra, on our transect it occurs only from Lang Crossing (5000') upslope, flying generally in late spring-early summer (May-July). It may co-occur with the weedy, colonizing Acmon Blue, but generally on different host plants. Lupini is slightly larger; the male is brighter blue (less violet) and has a black inner border on the orange hindwing lunules above; beneath the ground color is more ashen, the black spots rounder and smaller but quite distinct, and the iridescent scales near the hindwing margin quite pronounced. The female may be quite blackish above and rarely has as much blue as the female cold-season form of acmon ("cottlei"). The Lupine Blue occurs with its host, often on rocky balds and in alpine and subalpine "rock gardens;" males puddle, and both sexes often visit Pussy Paws.

Plebejus saepiolus

admin — Sun, 28 May 2006 18:07:59 +0000

Abundant on cool montane meadows, on our transect Lang Crossing and up (including Sierra Valley), where it flies just above the ground. The sexual dimorphism is extreme, and all our females are brown. High-altitude specimens may have the black spots beneath rather large and squarish. Adults visit low flowers, especially those of clovers, and males puddle. This species usually co-occurs with the Sonoran Skipper and the Nevada Cloudy-Wing and, often, with the Gray Blue. It has one brood, beginning early in the season (June to August, rarely later) and on our transect the host plants are native clovers (Trifolium) growing in damp to wet habitats.

Plebejus shasta

admin — Sun, 28 May 2006 18:07:58 +0000

Despite its name, the Shasta Blue does not occur on Mount Shasta. It is a high-altitude species. It formerly occurred at Donner but seems to be extinct in my site, though it persists at 8000' at Sugar Bowl, e.g. It is common at Castle and Basin Peaks, occurring in alpine rock-garden habitats where it generally flies from mid-season onward (July-October), along with the Sooty Gossamer-Wing. It flies near ground level, often basking with wings open, and visits Sulphur Flower (Eriogonum umbellatum) more than any other flower. However, unlike the Euphilotes blues in the same place and visiting the same flower, it itself is a Legume feeder, known to eat Whitney's Locoweed (Astragalus whitneyi) at Castle Peak, and perhaps one or more Lupines as well. In the northern Sierra this species occurs mostly on volcanic rather than granitic substrates. It has been suggested, but not verified, that it has a 2-year life cycle. Since it is present every year, that would require it to have either sympatric "odd" and "even-year" populations, or a lot of slippage in the system.