Bob Berry peers through his illuminated magnifying glass and picks through the carpet of insects with a pair of silver tweezers.

Thousands are massed before him on a white sheet of paper. Across the table, on other sheets, are tens of thousands more. One sheet contains a mound several inches high and the notation: "100,000 . . . count them if you like."

They are dead Maryland mosquitoes. Berry, a veteran Eastern Shore entomologist, plans to sort through such piles for one species: the kind that carries West Nile virus.

Although there have been no local cases of the mysterious mosquito-borne illness that has killed five people and sickened 35 in the New York area, Maryland officials plan to begin scanning local mosquitoes for the virus as early as this week.

Every summer for the past five years, state experts have checked the local mosquito population for the much more dangerous eastern equine encephalitis virus, in the hopes of catching it before it spreads to humans.

Now, with the outbreak of the similar illness in New York and with the local mosquito population enlarged by recent rains, state officials are worried that the coming southward migration of birds that carry the disease may bring it here.

Officials said they plan to start setting traps baited with dry ice this week in Prince George's County, Baltimore and other places, specifically for the Culex pipiens, the northern house mosquito, which is believed to be the main carrier of the new virus.

"We'll be doing a lot of trapping on the outskirts of Washington and Baltimore all the way over here to the Eastern Shore," said Cyrus R. Lesser, director of the state's mosquito control program. "We're planning on [this] week to start trapping and, hopefully, to have the lab set up with the necessary" materials.

"The Culex pipiens . . . is more of a suburban, urban type of mosquito in its ecology; in other words, the larval habitat is more associated with people," he said. "Polluted water, storm drains, sewage, things like that. . . . So metropolitan areas will be looked at."

The disease, which had not been seen in the United States before, is transmitted to humans by mosquitoes, which pick it up by biting infected birds. Though it can cause death in the elderly, experts say most people who get the disease do not become seriously ill.

Any local search for the West Nile virus will be based in a small complex of laboratories operated by the Maryland Department of Agriculture near Salisbury, where the annual summer and fall eastern equine virus survey takes place.

And it is there that Berry, 67, a state entomologist who is technically retired, will sort through the heaps of dead insects, in search of the Culex pipiens.

Lesser said the state also may scan other mosquito species for the new virus. Culex pipiens is the main culprit, he said, "but in Israel and India and other places, there are a lot of other Culex species involved. . . . It stands to reason that other Culex in North America would also be possibly transmitting the disease."

One day last week, Berry sat before several large mounds of dead mosquitoes--some caught as recently as Tuesday on Assateague Island--sorting through the tiny corpses with his tweezers.

"These are a lot of taeniorhynchus," he said, referring to the Aedes taeniorhynchus mosquito, as he sorted under the illuminated magnifier attached to a lab table. "There's a sollicitans. They have a ring around their proboscis, a white ring. . . . There's three or four Culex."

Berry, who ran the state's mosquito control program on the Eastern Shore for 20 years until he retired four years ago, can identify most of the 58 types of Maryland mosquitoes by sight: the sollicitans, with the distinctive stripe down its back; the smaller, less hairy pipiens.

Under his microscope, the distinctions are even clearer and the insects' construction striking. Generally, they are starved- and withered-looking creatures when not swollen with blood. They have creepy-looking leg stubble, frost-like body scales, a delicate fringe on the outer edge of their wings and a proboscis that looks like a sharpened gun barrel.

Thursday, Berry was gleaning mosquitoes that had been caught on several farms near Shelltown, in Somerset County, because his office had just learned of an encephalitis case in the child of migrant workers there in July.

"He had symptoms, but there was no definitive way to measure what caused it," Berry said of the child. Encephalitis, an inflammation of the brain, can be caused by many things other than a mosquito-borne virus.

Patti Beauchamp, communicable disease supervisor for the Somerset County Health Department, said Friday that the child had survived, that no other cases had cropped up and that the mosquito tests were negative for the equine virus.

Berry's examination is part of the annual mosquito survey the state has conducted once a week each summer and fall since 1994 to check for the virus that causes eastern equine encephalitis, also called triple-E.

Eastern equine encephalitis, which has a much higher death rate than West Nile fever, appears periodically along the Atlantic seaboard and is transmitted mostly by the Aedes sollicitans and other salt marsh mosquitoes.

No triple-E virus has been found this year in any of the 15,000 mosquitoes examined.

Three years ago, it was found in 10 emus in Eden, south of Salisbury, and eight of the large flightless birds died, said Bob Robison, the state scientist who runs the genetic scans for the virus. In recent days, the virus killed a horse in Chesapeake, Va.

The last eastern equine human fatality in Maryland occurred in 1989 in Dorchester County.

As Berry selected mosquitoes, he placed them in two-milliliter plastic vials--50 per vial--and carried a plastic trayful to an adjacent building where Robison, clad in shorts, white lab coat and blue rubber gloves, waited to test for triple-E.

Robison took each vial, poured in a reagent solution and placed into the vial the probe of a "sonic dismembrator," which, like a high-tech eggbeater, churned the contents into mosquito soup.

The soup then would undergo a complex scientific process in which Robison would be able to conduct a kind of litmus test for the presence of the genetic material of the eastern equine virus.

Robison said he cannot scan for the West Nile virus because he lacks the Culex pipiens mosquitoes, which are not normally trapped, and information on the different testing procedure, which he hopes to get from the federal Centers for Disease Control and Prevention.

"By doing this type of surveillance," he said, "we can find out whether or not these mosquitoes are carrying this virus. If they are, then . . . [we] can go in there and take corrective measures to kill off the mosquitoes with insecticide, before people get bitten."