U.S. Fish & Wildlife Service

Sacramento Fish & Wildlife OfficeServing the people, conserving the fish, wildlife, and plants of California

A Unit Of The Pacific Southwest Region

Kids' Species Information

Bay Checkerspot Butterfly

Photo by John Cleckler, USFWS

Bay Checkerspot Butterfly


Threatened. This means that we are worried about the butterflies but they are not in danger of extinction right now.


The bay checkerspot is a medium-sized butterfly. It has a wing span of little more than 2 inches.

Forewings have black bands along all the veins on the upper surface. These contrast with bright orange and white spots.


Caterpillars: dwarf plantain and purple owl's clover. Adults: nectar.


A certain kind of soil called serpentine. This soil is high in magnesium and heavy metals. It is low in nutrients—nitrogen, phosphorus and calcium. The species' food plants can grow there. Most other plants can't. So the plantain and owl's clover can grow without being crowded out.


You probably know that caterpillars turn into butterflies. Here is how it happens in Bay checkerspot butterflies.

Adults can be seen flying around from about late February to early May. Each of them only lives about 10 days.

Males emerge about four to eight days before females. Soon after the females emerge, they mate. Males can mate many times, while most females mate only once.

Eggs are typically laid in March and April. Females lay up to five egg masses of 5 to 250 eggs. The eggs are laid at the base of plantain, owl's clover or paintbrush.

Caterpillars hatch from the eggs in about ten days. They grow for two weeks or more, shedding their skin three times. Then they rest during the summer. (This phase is called diapause. It is sort of like hibernation.)

When the rainy season comes, the caterpillars become active again. Then they spend the winter in a shell called a chrysalis (like a cocoon). This is called the pupa stage.


All Bay checkerspots live in the area around San Francisco Bay in San Mateo and Santa Clara counties.


Habitat loss and fragmentation. Extreme weather. Air pollution. Pesticides. Vehicle strikes. Fire. Overgrazing. Gopher control. Illegal collecting. Invasive species.


Do you live near the San Francisco Bay? You may be able to help restore the Bay checkerspot's home. Search the Internet for Bay checkerspot butterfly volunteer. People are needed to pull weeds and plant native plants.


If you live in the San Francisco Bay area, you may see a Bay checkerspot. Wherever you live, you can watch butterflies.

KQED radio station has a great web page (330 KB PDF). The page has information, lesson plans, web links and field trip ideas.

Talk to your parents about planting a butterfly garden. See More Reading below.


A good field guide to common butterflies is Peterson First Guide to Butterflies and Moths by Paul A. Opler. Houghton Mifflin, 1998.

The same series includes Peterson First Guide to Caterpillars by Amy Bartlett Wright and Peterson First Guide to Insects of North America by Christopher Leahy. The latter book will teach you how biologists classify species.

Make a butterfly garden. See Audubon Magazine, May-June 1999.

We are partners of the Butterfly Conservation Initiative.

Don't be put of by the name of the Children's Butterfly Site. It has lots of good stuff.

Life on the edge: a guide to California's endangered natural resources, edited by Carl Thelander, has information about lots of species. It is published by BioSystem Books. See the Bay checkerspot species account on pages 430-31.

Visit the online Essig Museum of Entomology - California's Endangered Insects.

Photo Credit: John Cleckler, U.S. Fish & Wildlife Service.

Words to Learn

Scientists who study insects are called entomologists.

Entomologists call Bay Checkerspot butterflies Euphydryas editha bayensis. Scientific names are in Latin or Greek.

The Bay checkerspot is a subspecies. Entomologists add bayensis for "bay" to the species name of Euphydryas editha.

Bay checkerspots are in the Nymphalidae (brush-footed) family. This family is found on every continent except Antarctica.

Larva (plural larvae)—The technical name for caterpillars.

Pupa (plural pupae)—The stage in which a caterpillar turns into a butterfly.

Chrysalis (plural chrysalides)— Cocoon-like shell in which the caterpillar turns into a butterfly.

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Last updated: November 29, 2017