Most of us shoo, swat or squish bugs without a second thought, but when Charles Mitter sees one--especially an exotic one he's never encountered--he first asks a question: Which species are you?

Then he kills it, to find out.

Mitter, an entomologist, together with students and colleagues, plugs information about the bug's DNA into five computers. The computers think for as long as two weeks and render judgment on the bug's ID.

"That's systematics," said Mitter, who runs the Maryland Center for Systematic Entomology at the University of Maryland in conjunction with the Smithsonian Institution and the U.S. Department of Agriculture. Specifically, the program determines how bugs are related to one another and how they evolved.

Of 60 similar programs in the country, Mitter's graduate program, incorporating molecular biology and computer science, is outranked in quality only by that at Cornell University, according to an informal survey conducted by the University of Florida.

And it's not an ivory-tower field. Knowing the evolutionary history of a bug and how species are related can have a practical effect when, say, a strange new bug is accidentally introduced in your town from another part of the country or from abroad. Combating it to prevent the spread of disease or the death of crops may depend on having a clear picture of its genes and relatives.

"Knowing [an insect's] closest cousin, we can figure out what a natural enemy might be and introduce them into the area," Mitter said. Finding that close cousin is easier because of the work in Mitter's College Park program.

In labs filled with teenage termites, tarantulas on treadmills and bags of breeding beetles, the dozen or so students at the systematics center have analyzed the DNA of about 400 butterfly and moth species, 200 arthropods and other insects. That effort, spearheaded by professor Jerome Regier, created one of the most extensive databases of genetic bug information in the country.

"I can safely say no graduate program is looking at . . . arthropods and butterflies like we are," said Jeff Shultz, an entomologist who works with Mitter at Maryland.

"They don't just swing butterfly nets anymore," said May Berenbaum, chairman of the Entomology Department at the University of Illinois and former president of the Council of Entomology Department Administrators.

Those who conducted the University of Florida survey noted in particular the Maryland program's close collaboration with the Smithsonian, which has a collection of 30 million individual insects. That access helps students link the computer-generated information about a bug with the real thing.

Berenbaum, who did an external audit of Maryland's Entomology Department, said that Mitter's strength lies in not taking himself too seriously and working closely with entomologists doing other forms of entomology.

One such scientist is Barbara Thorne, who studies the social behavior of 600 colonies of termites. Taking an almost motherly interest, she uses information from systematics to interpret the evolution of bug behavior.

"I have babies and teenagers here," Thorne said, pulling the lid off a round plastic container filled with chomped wood and brimming with the wee whitish bugs. "When they are old enough, they fly off to mate. . . . They have one night of freedom."

After that magical night of courtship, she said, termites drop their wings and burrow into the ground, making a nuptial chamber for themselves. There, they will make so many babies that eventually the family population will approach that of, say, Las Vegas.

Although termites have brains about a millionth the size of a human brain, Thorne has become deeply acquainted with the termite mind-set and finds it fascinating. Long before the ideas of Plato or Thomas Jefferson, termites created their own version of fair societies, she said.

"It is very provocative to think about," she said. "It is very egalitarian and organized."

Thorne also has figured out how to kill the pests, which, after all, dine on homes. She has three patents for what she calls "termite cookies" used by commercial exterminators.

"It is a bit gross," she said. "It is chemical. They exchange materials mouth-to-mouth that relay information.

"I give them [the bait] . . . and they take it back and pass it around," which kills them.

So much for motherly affection.

For Shultz, who helped to lead the systematic study of arthropods, it is not the mind-set but the moves of his bugs that hold the allure.

He hooks up wires to the leg joints of his scorpions and tarantulas, sets them trotting on his buggy treadmill, rolls the videotape, flips on the computers and gathers data about stepping patterns.

"This guy has a pressurized body," Shultz said, gesturing to a shuffling three-inch-long whip scorpion. "Moving a knee joint is sort of like bending a hose and letting it go."

In addition to being able to reconstruct the evolutionary history of his arthropods, Shultz is able to look at whether bugs who walk the same might be closely related. If not--if unrelated insects evolve in similar ways--Shultz said that just adds more weight to the argument for evolution.

Naval and National Aeronautics and Space Administration scientists hoping to create walking machines for use under the sea, inside volcanoes and in space have used Shultz's findings for inspiration in engineering problems.

The cooperation among the scientists at Maryland is unusual, Berenbaum said. Generally, those interested in "pure science," such as the systematists, and those interested in "applied science," such as Thorne, don't get along too well, she said. At Maryland, everybody seems to relish the study of insects, she said.

"We happen to think everybody else is missing something that is all happening under their noses," Mitter said. "Bugs rule."

And rule they do, in more than a few ways, Mitter said.

First, they have the numbers. There are 10 quintillion. For every human being on Earth, there are hundreds of millions of insects.

Second, they were here before us. Bugs predate even dinosaurs by as much as 100 million years.

Third, if insects didn't flit about, plants would never be pollinated and reproduce, gutting our food chain.

Finally, bugs can spread disease among humans and wipe out our crops.

With that kind of pest power, the entomologists at Maryland go out of their way to educate the public about insects. Maryland residents can call a hot line (1-800-342-2507) to get answers to almost any bug-related question. The hot line gets about 50,000 calls a year, and entomologists give local folks training on things such as how to keep the pluck in their plants without resorting to pesticides.

CAPTION: Barbara Thorne, shown with containers of wood and termites, studies the social behavior of 600 colonies of termites.

CAPTION: Giant red velvet mites at the Maryland Center for Systematic Entomology.