A Rare Closeup on the Delta Green Ground Beetle, a Predator of the Pools

The quarter-inch long and brilliant green Delta green ground beetle is "still a bit of a mystery," even to experts.

March 21, 2024
A close-up view of the iridescent Delta green ground beetle. (Dan Osipov)

There is only one place you are likely to spot the brilliant green Delta green ground beetle, and that is Jepson Prairie, nestled amid Solano County’s farmland ten miles south of Dixon.

Even in spring, the busy season for beetles and other denizens, the prairie doesn’t look like much—a windswept, sky-filled playa pool; smears of yellow or white across the mostly flat green;  wire sheep-fencing running through muddy ditches. “It just looks like a swamp,” says photographer Dan Osipov, a Danville resident, recalling his first time at Jepson, last spring.

Until you bend down, and your mind is blown. 

Jepson Prairie—a 1,566 acre site with over 400 species—is in bloom. (Kate Golden)

For Jepson, a 1,566-acre site owned by the Solano Land Trust, is a fount of biodiversity in miniature, with over 400 species—including many that are rare, threatened or endangered, because most of California’s vernal pools have been destroyed by human development.

A vernal pool is a place of spring hustle, because the pools fill with rain in the winter and dry up in the summer. The quarter-inch-long Delta green ground beetle (Elaphus viridus) is thought to emerge from the ground in late winter, and scuttles along the margins of Jepson’s pools in spring, hunting for prey—springtails, mostly, and midges and other larvae. The females then lay probably one generation of eggs a year. Once the vernal pools dry up, the beetles crawl into the cracks in the mud. Larvae sit tight all summer as dormant pupae underground; some adults may make it through the summer.

But 40 years since they got on the federal endangered species list, U.S. Fish and Wildlife Service’s Amber Aguilera, at the Sacramento office, describes them as “still a bit of a mystery.” Few endangered species get the bald eagle treatment, moneywise. Nobody knows how many beetles there are, nor whether they are increasing or decreasing, nor even the basic facts about how they live and die, according to the agency’s 2020 review of the beetle’s status. Delta green ground beetles are threatened by their presumably tiny population size, limited range, non-native species, climate change, and all sorts of human development.

If you go: Jepson Prairie

Docent-led tours at Jepson Prairie are each Sunday and cover an astonishing number of species in a short length of trail—we didn’t even talk about the flowers here.

The cost is $5; no pre-registration is needed. Pro tip: check out the Jepson Prairie species handbooks, available for sale at the tours for $10.

You can also do a self-guided tour, in the public parts of the prairie. Learn more on the Solano Land Trust’s page.

More reading: Vernal Splendor, from Bay Nature’s Spring 2011 Issue

Osipov learned about these endemic beetles on one of the Sunday-morning spring tours at Jepson, where docents have a permit to collect the aquatic critters temporarily, to show visitors. He did some research, and this winter came back to stalk them a few times, looking for the springtails they eat. On overcast days they were nowhere. Then, on a sunny day in February, he saw three of them running around. “They’re calm enough that they would pose for a photograph,” he says. 

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Light reflects off the back of the Delta green ground beetle. (Dan Osipov)
Most Delta green ground beetles have these bronze spots pictured above, but some may be uniformly green instead. (Dan Osipov)
In the vernal pools, the Delta green ground beetle is a predator. It is thought to feed mainly on springtails, sometimes snacking on other larvae. (Dan Osipov)

A U.S. Fish and Wildlife Service spokesperson, Meghan Snow, wrote that the biologists who confirmed Osipov had shot the Delta green ground beetle were “SO jealous/excited” to see such photos. 

Osipov shared the images with Bay Nature hoping to bring some attention to these special beetles—especially with news of a tech-billionaire-funded effort to build a new city from scratch in Solano County, not far from the beetle’s home turf. “The reason why it’s been able to survive for so long is that it’s in the middle of nowhere,” Osipov says. 

About the Author

Kate Golden is Bay Nature's digital editor. Her background is in investigative, data-driven, and science journalism, and she has reported from rural Australia to the Bering Sea. She is also an artist, cyclist and sailor. Send tips to kate at, or find her on IG at @meownderthal.

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