Meet the beetles

Droves of black beetles have been spotted all over Costa Mesa and surrounding areas, marking what some entomologists call the biggest population explosion of its kind in many years.

The Calosoma beetles, which experts identify as predacious ground beetles, are not dangerous to humans and pose no threat to vegetation; their large bodies and threatening mandibles, however, have some residents frightened.

A couple of felled pine trees near Laura Yourex’s Mesa Verde home housed hundreds of the beetles.

“It’s freaking me out. They came over the fence in 20s and 30s. I’m not going out of my house,” Yourex said.

Entomologist Nick Nisson, who works in the Agricultural Commissioner of Orange County’s office, remembers a similar outbreak of the beetles in 2000, but said this one is much worse.

This summer’s influx is caused by a combination of rainfall and warm temperatures, which increases the number of worms that the beetles eat, he said.

“Most people consider them beneficial because they’re eating insects that are considered pests, but some people don’t like them because they’re ugly,” Nisson said.

Ron Vanderhoff, Daily Pilot columnist and nursery manager at Roger’s Gardens in Newport Beach, said they put some customers on edge.

“People want to buy something to kill them all. They want some kind of spray to get rid of them,” Vanderhoff said.

But he tells them to wait three or four weeks, until the beetles’ food supply diminishes and their population naturally subsides. About a year ago, Newport Beach had an outbreak of diaprepis root weevils, which were a non-native species that destroyed vegetation, unchecked by natural predators.

The state is still in the process of exterminating the weevil by spraying poison, but no similar action will be taken to curb the population of the ground beetle because it’s a native species that will eventually decrease in population on its own, according to John Kabashima, environmental horticulture advisor for the University of California.

“Fortunately, we live in a dry environment, so the high populations we are experiencing are a transitory phenomena that will become the subject of stories told by gardeners and golfers to their children, as the great ‘predacious ground beetle invasion of 2008,’” Kabashima said.

If homeowners can’t live with the beetles even for a short time, though, Kabashima recommends removing piles of leaves and stones, where worms like to live.

ALL ABOUT BEETLES

Scientific Name: Calosoma (commonly known as predacious ground beetle)

Eat: A variety of worms, but no vegetation

Found: In grassy areas, piles of leaves and other moist areas

Cautions: They don’t bite humans, but picking them up might lead to pinching.

Extermination: Experts and officials agree that there is no reason to exterminate the beetles because they are a native species. Their population will decline when the food supply decreases, and the current high populations probably won’t last more than a couple of weeks.

ALAN BLANK may be reached at (714) 966-4623 or at alan.blank@latimes.com.