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The Bay Checkerspot butterfly will continue to need friends if it is ever to repopulate Edgewood County Park and Natural Preserve in Woodside. To that end, volunteers will help distribute caterpillars at the park on Thursday, Feb. 21, and Sunday, Feb. 24.

The Checkerspot is one of two California butterfly species that the U.S. Fish & Wildlife Service lists as threatened along with 11 others listed as in danger of extinction. The butterflies went extinct in Edgewood Park in 2003, park officials say, two years after Edgewood and other areas were declared part of the critical habitat for the Checkerspot.

The larvae and caterpillars for this project come from Coyote Ridge in south San Jose.

This reintroduction is one of a series that started in 2007. The butterflies at Edgewood are believed to have lost a critical part of their habitat due to the park's close proximity to Interstate 280. The nitrous oxides and ammonia from vehicle exhaust act as fertilizers and encourage non-native grasses at the expense of the native wildflowers that the caterpillars like, according to Field Biologist Stuart Weiss in a Parks Department document.

Volunteers restored native grasses to a 15-acre area through a grant program by Pacific Gas & Electric Corp., according to this account, and careful monitoring and "rotational mowing" will prevent a re-infestation of the non-native grasses.

Partnering with the San Mateo County Department of Public Works and Parks in this volunteer effort are the Friends of Edgewood County Park and Natural Preserve, the California Native Plant Society and San Mateo County Parks Foundation.

Click here to read what the Friends of Edgewood Park and the Bill and Jean Lane Education Center have to say about the butterfly.

To get to Edgewood Park, take the Edgewood Road exit east from Interstate 280, travel about one mile, and turn right into the parking lot.

— Dave Boyce

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