Time flies, and flies sometimes tell time

November 06, 1990|By Frank D. Roylance | Frank D. Roylance,Evening Sun Staff

You may find Ted Suman's back-yard research into the life cycles of blow flies and flesh flies intriguing. It's also important to Maryland law-enforcement authorities.

But nobody finds it very appetizing. If you haven't had dinner yet, go eat now and come back to the paper when your meal has settled.

The grim fact of the matter is that blow flies and flesh flies are among the first creatures to visit the dead -- sometimes within seconds of death. And their progress in disposing of a human body before the first people stumble upon it can provide investigators with valuable clues for pinpointing the time of death.

And that can sometimes help lead police to a murderer.

Suman, 54, is an entomologist -- an expert on insects. He teaches biology at Anne Arundel Community College in Arnold. And, except for his attraction to a phenomenon that sends most people running, he appears to be quite normal -- a warm and amiable man with a boyish sense of curiosity about bugs.

That's probably why his wife and three daughters didn't flinch much when he proposed, a while back, to set raw pigs' brains out in their back yard in Easton so that he could study the flies that arrived to breed in the pungent mess.

"They're used to me," Suman said with a wry smile. In fact, the women even donated their old panty hose, which Suman used as screens to keep unwanted insects from his experiment.

His mission in entomology, he said, is to find ways to "use insects to solve a problem, rather than to simply be a pest-control problem."

He isn't the first. Suman tells the story of a ruler in ancient China who used flies to identify which of several farmers had slain a local man.

The ruler had all the suspects lay their sickles out on the ground, and accused the one whose blade was soon covered with flies. They were attracted by unseen traces of blood.

Coroners and medical examiners in Maryland and some othejurisdictions have for years used the presence of insects as clues to the puzzle of how long victims of suspicious deaths have been dead.

But Maryland's chief medical examiner, Dr. John Smialek, said, "We were using an estimate, that it was approximately six or seven days for the larval phase of development, then approximately an additional week for the pupal stage to be completed."

The possibility existed, he said, that those times might not be very accurate for Maryland flies and weather conditions.

Dr. Franco Introna, then a research assistant in Smialek's office, suggested that Suman launch a study that would generate an authoritative set of data -- specific to Maryland -- that investigators could use to translate fly development into elapsed time since death.

collect the data he needed, Suman set about building a cage of chicken wire in his back yard. He diplomatically kept his next-door neighbor only vaguely aware of the nature of his work.

The chicken wire was designed to keep out raccoons and other small mammals. Inside the cage, Suman set out jars of fresh pig brains -- chosen because of its similarity to human flesh, and because it stays soft.

Easton's flies found the pig brains in seconds.

"When I was carrying the brains over to the research sites, they were on it right away," Suman said.

Soon, eight species of fly had visited the brains. As minutes turned to hours, Suman screened out late-comers with the pantyhose, then watched and recorded the flies' progress.

Four types of green bottle flies, and two species of blue bottle flies had quickly laid their eggs, and the eggs soon hatched into larvae, called maggots.

"If they lay eggs in the morning, they can be larvae in the afternoon," Suman said.

Two kinds of the larger, dull-black flesh flies also found the bait, but their species lay live larvae, ready to start eating.

Fly maggots are tiny, white, carrot-shaped eating machines. "The whole front end is practically nothing but mouth parts," Suman said, "and it's constantly eating. It's incredible how fast they can reduce meat."

As the maggot grows, it molts out of its skin three times, and Suman was there to measure them and to record the times and temperatures at each stage.

When full grown, the larva stops eating, moves away from the rotting flesh and forms a pupal case, like a cocoon, where it begins its transformation into an adult fly.

From egg to adult, Suman said, takes roughly 20 days, depending on fly species and temperature. Within that time period, he said, the fly data can pinpoint the time of death accurately to within hours soon after death, or within a day later on.

After 20 days, however, "You can't really do well using life history data," he said. The overlapping life cycles of late arrivals and succeeding generations of flies begin to confuse the issue.

At that stage of decomposition, other indicators must be used -- such as the succession of beetles and other species that follow the flies.

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