GARDEN GROVE — While other gumshoes strap on their 9-millimeter pistols when called to a murder scene, Jim Webb packs his butterfly net.

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Upon arrival, he may not even notice the shell casings, blood splotches or murder weapon and steps right over the corpse itself.

"I'm not a real cadaver fan," Webb says. "I'm just interested in the bugs."

The only forensic entomologist in Orange County, Webb is part biologist and part detective. He is among a new breed of investigators who have made a career from the simple fact of nature that bugs are often the first--and only--witnesses to murder.

By studying insects found around dead bodies, Webb can help determine when a victim died, whether cocaine or other drugs were involved and if someone moved the corpse.

The insects can leave helpful clues that sometimes lead detectives to the culprits. Webb once helped link a suspect to a strangling by matching up telltale chigger bites on the suspect and others who had been at the crime scene.

"The guy can do wonders," said Bill Green, an investigator for the San Diego County district attorney's office, who recalled a serial murder case in which Webb used maggots to peg the time of death of one victim and poke holes in the killer's alibi.

Nationwide, there are fewer than 20 forensic entomologists who do criminal investigations on a regular basis; only three are in California. Webb, 53, is considered a pioneer in his field and typically handles five to 10 cases a year in Orange and Los Angeles counties, and across the state.

In this esoteric and expanding discipline, Webb and his colleagues talk in terms of \o7 Calliphora vicina, Phaenicia sericata \f7 and \o7 Chrysomya megacephala--\f7 all species of blowflies in Southern California that typically are the first insects to hover over a dead body. (That's why Webb packs his butterfly net.)

Instead of motive, these sleuths concentrate on the weather, which can hinder or spur insect breeding. They look at crime scenes in terms of the amount of sunlight, not cross streets. Their file cabinets are loaded with critters soaked in alcohol.

Over breakfast at annual symposiums, these scientists swap photos of cadavers infested with maggots and beetles the way new parents show off baby pictures.

"I wake up every day looking forward to coming to work," said Webb, whose county office is in a dusty Garden Grove trailer, decorated with drawings by his 8-year-old daughter and blowups of rats and maggots and flies.