The Bay checkerspot (Euphydryas editha bayensis) is a butterfly endemic to the San Francisco Bay region of the U.S. state of California. It is a federally threatened species, as a subspecies of Euphydryas editha.
Since the 1980s the population of checkerspots, the Euphydryas species and subspecies, has been in serious decline. This particular subspecies had been the subject of extensive study by researchers at Stanford University since the 1960s. Thus its vulnerability, particularly in light of rapid land development taking place in the San Francisco Bay Area, was recognized by this group of researchers. Consequently, in 1980 they petitioned the U.S. government to list this checkerspot subspecies as endangered. This led to a prolonged and contentious review by the U.S. Fish and Wildlife Service involving scientists representing arguments for and others against listing and numerous public hearings. The service finally conferred federally threatened status designation in 1987.
Recently, two authors have advocated a reclassification for this subspecies of the checkerspot common to western North America, Euphydryas editha. The classification, to Euphydryas editha editha, is for reasons of historical precedence; however, this has not been accepted by the scientific community.
Description
The Bay checkerspot butterfly is a medium-sized butterfly with a wingspan of slightly more than . As a member of the family Nymphalidae the checkerspot is part of a group of brush-footed butterflies. The insect's forewings are marked with black bands along the veins of the wing's upper surface. It is the black banding that gives the Bay checkerspot its unique appearance and its name. The bands contrast sharply with bright red, yellow and white spots.
The Bay checkerspot differs from other checkerspots, with characteristics differing:
from the LuEsther's checkerspot (Euphydryas editha luestherae) by being darker, it also lacks the relatively uninterrupted red band on the outer wing which the LuEsther's checkerspot has. from the island checkerspot (Euphydryas editha insularis) by being not as dark and brighter red and yellow than, which lives on the Channel Islands and nearby mainland. from other subspecies such as the Quino checkerspot (Euphydryas editha quino) or the Mono Lake checkerspot (Euphydryas editha monoensis) by having black bands that give the Bay checkerspot a much more checkered appearance than they have.
The subspecies was first described, as Euphydryas editha var. bayensis, by Robert F. Sternitzky in 1937.
Life cycle
Adult butterflies emerge in early spring. The adults, which live an average of ten days emerge during a six-week period from late February to early May. The male Bay checkerspot typically emerges four to eight days before the female. The males have one goal, reproduction. They find and mate with a female immediately upon emerging. The male mates many times while most females mate only once during the flight season. Besides mating the adults spend time foraging for nectar and for the females, laying eggs.
The eggs are usually laid in March and April. The adult female will lay up to five masses of eggs which contain 2 to 250 eggs each. The eggs are deposited at the base of the dwarf plantain plant or less frequently the owl's clover or paintbrush. The eggs take about ten days to hatch and upon emergence from the eggs the larvae grow for a period of two weeks or more during which they shed their skin until they reach their fourth instar. Any larvae that successfully enters the fourth instar enter a period of diapause that lasts through the entire summer. During diapause they spend time under rocks or within cracks in the soil. When the diapause ends they resume activity, feeding and move to complete their development into adult Bay checkerspot butterflies.
Diet
While the larvae are dependent on the host plants, mostly the dwarf plantain, for sustenance the adult butterflies live on nectar. They feed on a variety of plants associated with serpentine grasslands. Some of these plants include California goldfields, white turtlehead, desert parsley, scytheleaf onion, false babystars, intermediate fiddleneck and others. Female fecundity is dramatically affected by nectar availability.