The Bay checkerspot butterfly, a subspecies of Euphydryas editha, is a butterfly that lives in the San Francisco Bay and is unique for its white spots and bright orange contrasting wings.
Bay Checkerspot Butterfly Species Summary
| Scientific Name | Euphydryas editha bayensis |
| Family Name | Nymphalidae |
| Kingdom | Animalia |
| Genus | Euphydryas |
| Habitat | Open woodlands, grasslands, mountains |
| Range | San Francisco Bay region |
| Host Plants | Dwarf plantain, purple owl’s clovers, and Indian paintbrush |
| Butterfly Description | Bright yellow, black, and white spots arranged in a checker pattern |
| Caterpillar Description | Black with hairy growths and a dotted orange line |
Butterfly Physical Description
The Bay checkerspot butterfly belongs to the medium-sized species. Its wingspan is a bit more than 2 inches (5.1 cm). This butterfly belongs to the family Nymphalidae, and is a subspecies of Edith’s checkerspot.
Its forewings are marked with black bands along the veins on the wing’s upper side. This butterfly also has black banding, which is significant for easier recognition. The band contrasts with bright red, yellow, and white spots.
Checkerspot Butterfly Subspecies Description
There are a few other subspecies worth mentioning to help you differentiate them:
| LuEsther’s checkerspot (Euphydryas editha luestherae) | a bit lighter than the bay and has a continuous red band on the outer wing |
| Quino checkerspot (Euphydryas editha quino) | also lacks the black bands that Bay checkerspot has |
| Baltimore checkerspot (Euphydryas phaeton) | darker than the bay and has fewer white spots on its wings |
| Taylor’s checkerspot (Euphydryas editha taylori) | is extremely rare — only three reported in Canada and eight in Washington. It lacks contrasting coloration and is dark than the bay |
| Cynthia’s fritillary (Euphydryas cynthia) | comparatively are lighter and less red |
Why Are They Called Checkerspot Butterflies?
These butterflies are recognizable for their black, brown, and yellow checker-like patterns. Almost all butterflies of this species have similar marks on their wings, which give them the name.
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Caterpillar Physical Description
Once deposited, the eggs take about ten days to hatch. Once it reaches maturity, the larva is mostly black with numerous hairy growths and a dotted orange line vertically through the middle of its dorsal side. Chrysalis is whitish with uneven markings of orange and black, which looks similar to an adult butterfly.
Checkerspot Butterfly Lifespan
| Egg Stage | 10 days |
| Caterpillar Stage | 10 to 14 days |
| Chrysalis Stage | 14 days |
| Butterfly Stage | 10 days |
Where do checkerspot butterflies live?
This butterfly and its host plants thrive near serpentine soils derived from serpentinite minerals. The habitat is often divided into three general types.
- The first one is the primary habitat, around native grasslands.
- The second is “satellite islands, ” located in native grasslands.
- The third type is tertiary habitats — areas where larvae and plants can thrive that are not serpentine soils.
Still, due to climate change and the decline of natural resources, this species is rare. The main threat to this butterfly is the increasing emission of nitrogen in California.
Host Plants and Diet
The main larval host plants include dwarf plantain plant, purple owl’s clover and Indian paintbrush. However, these plants will only serve the caterpillar.
Adults feed on nectar from white turtlehead, desert parsley, scytheleaf onion, false babystars, and California goldfields.
White turtleheads, false baby stars, and goldfields are ideal garden choices to attract Checkerspot butterflies.
The larvae are dependent on the host plants, such as the dwarf plantain. Adult butterflies drink nectar. They also like a variety of food plants:
- Desert parsley
- California goldfields
- White turtlehead
- False baby stars
- Scytheleaf onion
Behavior after mating
The egg-laying process depends on the nectar availability. Females will lay up to 5 massive eggs, each containing 2 to 250 smaller eggs at the base of the host plant. The flight pattern is medium to fast, and males usually emerge 4 to 8 days before the females.
Are Checkerspot Butterflies Poisonous?
Some Checkerspot butterflies are considered dangerous for both plants and vertebrates. For example, Edith’s checkerspot’s eggs may result in the death of the host plant. Additionally, this species’ larvae, pupae, and adults are poisonous to predators.
Predators
These butterflies’ main predators are birds. However, predation is rare since Checkerspot butterflies are rare and scarcely distributed. Some subspecies of this butterfly are often victims of wasps and tachinid flies. In some cases, the larvae will twitch to deter predators and ingest toxins from the host plants.
Distribution
This species used to be present around San Francisco Bay area, mountains near San Jose, Oakland Hills, and several other locations near the city. With the area’s development during the 20th century, the butterfly habitat changed, and many Checkerspot subspecies are no longer that widespread.
Are Checkerspot Butterflies Endangered?
The current range of the Checkerspot butterfly has reduced drastically. For example, all subspecies noted in the federal register around San Mateo County are gone.
The ecosystem disturbances induced a decline of host plants, which affected the butterfly life cycle. Additionally, introducing non-native, invasive plant species used for cattle feeding brought competition with native plants that sustained the bay Checkerspot.
There were several conservation plans and attempts to recover the species. For example, 1,000 larvae were brought to Edgewood Park in February 2007, but this recovery plan did not affect the butterfly population. The subspecies was last seen at San Bruno Mountain in 1985 and at Jasper Ridge Biological Preserve in 1998.
Today, the Bay checkerspot has an ecology status threatened. The US Fish and Wildlife Service proposed that 8,300 acres in five states be declared critical habitats for this butterfly subspecies. All remaining populations are spread out the Santa Clara County, British Columbia, Oregon, and Washington.
Do Checkerspot Butterflies Migrate?
Bay checkerspots do not migrate. Still, there are records of short-distance travels, up to 5 miles away from their primary habitat.
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