U.S. Environmental Protection Agency
Bay Checkerspot Butterfly Euj^kydrytu tdiHui boy&wm
Pkffto source: T.W. Vaines © Cal^Wfua. Academy oj-Sciences
The bay checkerspot butterfly
is a threatened species.
Threatened species are plants,
and animals whose population
numbers are so low that they
may become endangered in the
future.
Endangered species are
plants and animals that are
in immediate danger of
becoming extinct.
The U.S. Environmental
Protection Agency's (EPA)
Endangered Species Protection
Program (ESPP) will help
ensure that pesticide use does
not jeopardize the survival of
listed species.
Description and Ecology
Status Threatened, listed June 18, 1987.
Critical Habitat Designated April 30, 2001.
Appearance The bay checkerspot butterfly typically has
a 2 inch wingspan. The distinct, black bands along all the
veins of the upper wing surface contrast sharply with the
bright red, yellow and white spots, giving the butterfly its
"checkerboard" appearance.
Range Historically, populations of bay checkerspot
butterflies were recognized in many of the counties in the San
Francisco Bay area. These included Contra Costa, Alameda,
San Francisco, and especially San Mateo and Santa Clara
Counties where the only known populations remain. These
populations are uniquely tied to no more than 12,000 acres
of native grasslands on serpentine soils, or similar infertile
soils. This infertility appears to have staved off the invasion
of European grasses and weeds, giving native plants and
the bay checkerspot butterfly a stronghold. On these soils
the distribution of the butterfly is patchy and demonstrates
meta-population dynamics. Only four or five core populations
support and are supported by a few other satellite
populations. These populations can undergo large fluctuations
and the ability to recolonize from one to another following
local extinctions is critical to the survival of the species.
Habitat The serpentine outcrops in Santa Clara and San
Mateo Counties harbor the native plants bay checkerspot
butterflies require. The primary larval food plant is Plantago
erecta, dwarf plantain. For those larvae who might not have
accomplished their fourth instar before plantain dries, the
near presence of Castilleja densiflora, purple owl's clover, and
Castilleja exserta, exserted paintbrush, is critical for the extra
food needed to reach diapause (i.e., a period of dormancy).
Nectar plants for the adults include California goldfields,
desert parsley, and tidy-tips. These native grasslands have
been more recently enriched by nitrogen-deposition, enough
to invite the invasion of alien forbs and grasses such as Italian
rye grass. Moderate grazing can help counter this invasion.
Within these serpentine grasslands a variety of thermal
microclimates created by variations in topography buffer the
impact of climatic variability. Larvae, as well as host or nectar
plants develop earlier on southern slopes; northern slopes
remain cooler and more moist as the season heats up. Both
slopes are essential to carry some of the population through
seasonal differences from year to year, and especially though
years of extreme weather.
Reproduction and Life Cycle The life cycle of the
bay checkerspot butterfly is tied to the life cycle of its host
plants. These plants germinate from early October to late
December and then senesce from early April to mid-May.
The emergence of the butterflies from pupae between late
February and early May correlates to the blooming of their
nectar plants. Feeding, mating and egg laying all occur during
this 4-6 week flight season. The females deposit up to five
egg masses in clusters of 5 to 250 eggs each at the base of
the larvae host plants, usually dwarf plantain, sometimes
purple owl's clover or exserted paintbrush. After hatching
the black larvae soak up the sun to warm themselves. Once
warm, they can travel to other host plants and a warmer
or cooler microclimate. By laying eggs in a variety of
microclimates and on a variety of host plants, the female
butterfly increases the chances that some of her offspring
will survive regardless of climate variation. The larvae eat
and cycle through their molts until reaching the fourth
instar. At this time they crawl under rocks or into cracks to
protect themselves through diapause, which lasts until the
next growing season. Some evidence suggests that during
extremely dry seasons larvae may continue diapause until a
second spring. With the onset of the rainy season diapause
ends and larvae resume feeding. Post-diapause, they are
larger and more able to travel in search of food plants, a
warm slope, or the right place to pupate, which is usually
suspended from vegetation just a few millimeters off the
EUpkydryM eetitha, bixymAM
Office of Pesticide Programs (7507P)
http://www.epa.gov/espp/
February 2010

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ground. Emergence to an adult butterfly occurs in 15-30 days,
depending upon thermal conditions. The normal life span of
the bay checkerspot butterfly (egg-larvae-pupae-butterfly) is
one year.
Recovery Plan The U.S. Fish and Wildlife Service (FWS)
developed a recovery plan for the bay checkerspot butterfly
in 1998. Recovery plans outline reasonable actions that FWS
believes are required to recover or protect listed species.
FWS prepares recovery plans, sometimes with the assistance
of recovery teams, contractors, state agencies, and others.
Recovery plans do not necessarily represent the views nor the
official positions or approvals of any individuals or agencies,
other than FWS, involved in the plan formulation. Approved
recovery plans are subject to modification as dictated by new
findings, changes in species' status, and the completion of
recovery tasks.
Bay Checkerspot Butterfly Information
Sources
Primary Reference Beacham, Walton, Castronova,
Frank F., and Sessine, Suzanne (eds.) 2001. Beacham's Guide
to the Endangered Species of North America, Gale Group,
New York. Vol. 3, pp. 1516-1518.
Listing Notice U.S. Fish and Wildlife Service. Federal
Register 52 No. 181, September 18, 1987, pp. 35366-35378.
http://ecos.fws.gov/docs/federal_register/frl327.pdf
Critical Habitat Designation u.s.
Fish and Wildlife Service. 2001. Federal Register
66, No. 83, April 30, 2001, pp.21450-21489
http://ecos.fws.gov/docs/federal_register/fr3740.pdf
Recovery Plan U.S. Fish and Wildlife Service, Pacific
Region, Portland, Oregon. 1998. Recovery Plan for Serpentine
Soil Species of the San Francisco Bay Area. 330+pp. http://
ecos.fws.gov/docs/recovery_plan/980930c_v2.pdf
Alternate host pbutfs, pwrpte-owi's clover cutd yellowgoldjields.
Image wurce: KQEO QUESTS&me rights reserved.
Image zource: KQEO QUEST Some rights resented.
T.W.Vavies © California Academy of Sciences

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