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Bay Checkerspot (Euphydryas editha bayensis)

The Bay Checkerspot is a threatened subspecies of Edith’s checkerspot butterfly, known scientifically as Euphydryas editha bayensis. Found in a very small region of the United States, this butterfly is celebrated for its distinctive black banding, which gives it its unique appearance and its name.

Bay Checkerspot Butterfly

Scientific Classification

  • Family: Nymphalidae
  • Genus: Euphydryas
  • Scientific Name: Euphydryas editha bayensis


Once widespread across the San Francisco Bay region, the Bay Checkerspot has seen its habitat significantly reduced due to urban development and changes in land use. This butterfly is now mostly confined to specific areas where conservation efforts are in place to protect its delicate ecosystem. Its survival is tightly linked to the presence of its host plants, and its life cycle and behaviors are adapted to the local climate and environment.

Description and Identification


The mature larva of the Bay Checkerspot is black with numerous small tufts of hair covering its body. A distinctive bright yellow or orange dotted line runs vertically along the middle of the dorsal side, making the caterpillar relatively easy to identify. These caterpillars feed primarily on specific host plants, which are crucial for their development and survival.


The chrysalis of the Bay Checkerspot is white with uneven orange and black markings, resembling the adult butterfly. This coloration helps in camouflaging the pupa against predators during this vulnerable stage.

Adult Butterfly

Sexual Dimorphism: Sexual dimorphism is not present in the Bay Checkerspot; males and females appear similar to the casual observer.

Color and Appearance: When the wings are open, the dorsal side of the forewings exhibits black bands along the veins, sharply contrasting with bright red, yellow, and white spots. The ventral side, visible when the wings are closed, mirrors the vibrant pattern of the dorsal side.

Euphydryas Editha BayensisBay CheckerspotAverage Wingspan: The average wingspan of the Bay Checkerspot is a little more than 2 inches (approximately 51 mm).

Flight Pattern: Bay Checkerspot butterflies exhibit a medium to fast flight pattern, often flying low to the ground as they move between flowers.


Female Bay Checkerspots can lay up to five masses of eggs, with each mass containing between 2 and 250 eggs. These eggs are deposited at the base of the host plants, where the larvae will have immediate access to food upon hatching.

Quick Facts

DistributionSan Francisco Bay region of California, USA
HabitatRidge tops, open woodlands, alpine tundra, grasslands, and rocky outcrops
Lifespan of AdultsThe adult Bay Checkerspot typically has a short lifespan, with adults emerging in the spring, mating, and laying eggs over a period of a few weeks
Host PlantsPlantago erecta, Castilleja exserta, Castilleja densiflora
Adult DietFlower nectar

How to Identify Bay Checkerspot?

Identifying the Bay Checkerspot butterfly involves looking for its distinctive black banding and colorful spots. The dorsal side of the wings features black bands along the veins with bright red, yellow, and white spots. These butterflies often inhabit areas with their host plants, so spotting these plants can increase the chances of finding a Bay Checkerspot. During the caterpillar stage, look for black larvae with bright yellow or orange dotted lines along their dorsal side. Observing these butterflies in their natural habitat, such as ridge tops and open woodlands in the San Francisco Bay area, can also aid in identification. The presence of specific host plants like Plantago erecta is a strong indicator of the Bay Checkerspot’s habitat.

Did You Know?

  • Male Bay Checkerspots typically emerge four to eight days before the females, a phenomenon known as protandry.
  • The Bay Checkerspot is considered an indicator species, meaning its presence or absence can provide insights into the health of its ecosystem.
  • Conservation efforts for the Bay Checkerspot often include habitat restoration and the planting of its host plants to ensure the survival of this delicate species.


The Bay Checkerspot butterfly, with its striking appearance and specific habitat requirements, is a fascinating and important species within the San Francisco Bay region. Conservation efforts are crucial for its survival, as habitat loss and environmental changes continue to threaten its existence.

Bay Checkerspot Pictures

Bay Checkerspot Butterfly Habitat

Bay Checkerspot Butterfly Images
Bay Checkerspot Butterfly Photos
Pictures Of Bay Checkerspot Butterfly
Images of Bay Checkerspot Butterfly
Bay Checkerspot Butterfly Pictures

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Scientific Classification

  • Family: Nymphalidae
  • Genus: Euphydryas
  • Scientific Name: Euphydryas editha bayensis
Published by Avatar on July 25, 2019.
Last Updated: May 30, 2024. ✅ Verified by: Butterfly Team