A New Way to Kill Mosquitoes
By TERESA RIORDAN

WITH the threat of West Nile virus and the invasion of fierce Asian tiger mosquitoes in his neighborhood in Arlington, Va., Donald R. Hall was beginning to worry about his young granddaughter playing outside.

So Mr. Hall, 60, who retired as an electromechanical engineer in the military and intelligence sectors to spend his days dreaming up inventions in his backyard skunk works, went on the offensive several years ago in the war against the mosquito.

Mr. Hall recently received United States patent 6,708,443, a wide-ranging patent covering several approaches that he contends might help control mosquito populations across wide areas such as wetlands or regions in Africa where mosquito-borne illnesses like malaria are rampant. Most of Mr. Hall's approaches rely on the same principal: killing the mosquito eggs rather than the mosquitoes themselves.

"They will breed in a bottle cap," Mr. Hall said. "The idea is to interrupt the life cycle."

…Another device Mr. Hall has invented is a shallow tray powered by what is known as a bimetal coil. As rainwater stagnates in the tray, which has a fine mesh at the bottom, it becomes an attractive spot for mosquitoes to deposit their eggs.

The coil - made of two different metals strapped together, each with different expansion and contraction rates - expands as it warms during the day, pushing the mesh above the water line. The mesh captures the eggs, which bake in the sun during the day. In the evening, the coil cools and contracts, pulling the mesh back under the water, waiting for more unsuspecting mosquitoes to lay their eggs.

Mr. Hall said such devices would require little or no maintenance and would be cheap to build, making them appealing for the developing world or for places where they would need to be distributed widely, such as wetlands.

"You could give them away," he said.