Thomas Eisner, a biologist known for revealing the hidden chemical arsenals that insects use to stave off attackers, woo mates and otherwise solve the basic problems of survival, died Friday at his home in Ithaca, N.Y. He had Parkinson's disease. He was 81.

Fascinated since boyhood by the smells and secretions of various insects, Eisner became known as the father of chemical ecology for his skill in figuring out how creatures use chemistry - including liver poisons, nerve drugs and scalding jets of toxic liquids - to interact with one another and the world at large.

His work exposed a landscape of seduction and deceit, full of dramatic survival stories that he told in scholarly journals, popular books and interviews. He was, along with his good friend Edward O. Wilson, one of the most respected and visible entomologists in the world.

A professor at Cornell University since the late 1950s, Eisner was also an accomplished nature photographer whose images were a compelling argument for the complexity and beauty of insects' thrumming, diverse world.

One of his most famous discoveries arose out of an encounter with a beetle that squirted him with a stinky brown liquid. With the help of a high-speed camera, he figured out that the bombardier beetle was employing a weapon system akin to the buzz bombs used by Nazis during World War II.

Threatened by a predator, the bombardier reacts with a precisely aimed shot of caustic liquid, which emerges at 26 mph and 100 degrees Celsius - the boiling point of water. The beetle was a "champion chemist," said Eisner, who was unabashed about his affection for insects and their inventiveness.

"Once you fall in love with them, you can't fall out of love," he told NPR in 2003. "There's no end to the marvel."

His discoveries were invariably triggered during walks outside. A keenly observant field biologist, he would notice an insect doing something curious, then hypothesize why and take his hypothesis back to the lab for testing with the help of engineers, chemists and other colleagues.

Over the years, working at field stations in Florida, Arizona and elsewhere, he identified how ornatrix moths trapped in spider webs persuade their captors to set them free; how palmetto beetles use adhesive feet to glue themselves to leaves; and how femme-fatale fireflies entice males with a mating dance, only to eat them and ingest a powerful, protective poison.

Eisner ranged so widely in his endeavors that Wilson, Harvard's eminent expert on ants and evolutionary biology, compared him to a pointillist in an interview with writer Diane Ackerman, who profiled Eisner in the New Yorker in 1992.

"He daubs touches of color on a broad canvas, which at first seem to be a random splattering of bright pigment, but, as more and more spaces are filled in, reveal an extremely interesting picture of a little-known part of the living world," Wilson said.

Thomas Eisner was born June 25, 1929, to Jewish parents in Berlin. With Hitler's rise, he and his parents fled to Spain in the early 1930s.

Then the Spanish Civil War pushed them onward to France and finally to Uruguay, where Eisner spent much of his youth among a wealth of insect life. He collected caterpillars, beetles and maggots, housing them in his bedroom until the family moved to New York in the late 1940s.

Eisner took his first entomology course at Harvard, where he realized, he said, "that a person could make a living working with insects." He graduated in 1951 and the following year married Maria Lobell, who became, along with Cornell chemist Jerrold Meinwald, one of his closest collaborators.

After college, Eisner continued at Harvard and befriended Wilson, a fellow graduate student, before receiving a doctorate in insect physiology in 1955. Eisner joined the Cornell faculty in 1957.

Over the years, he published hundreds of scholarly papers and at least nine books, including "For Love of Insects," which was widely praised as an accessible, ebullient first-person account of Eisner's exploits in science.

He received numerous professional awards, including the 1994 National Medal of Science, the United States's highest scientific honor.

He was a fierce advocate for conservation. Only a tiny fraction of the world's insects have been described, and the millions living in threatened habitats around the world may harbor chemicals that could solve stubborn problems in medicine and other fields, he said.

"The natural treasury of chemicals are disappearing faster than we can keep track, before we've even assessed the resources," he told NPR.

Eisner believed that chemical prospecting, or looking for valuable chemicals in flora and fauna, could play a key role in encouraging developing countries to preserve wild places. In 1991, he helped broker a landmark deal between Costa Rica and the pharmaceutical giant Merck in which the company agreed to pay royalties on any drugs developed from Costa Rican plants and animals.

Despite his concern for the future, Eisner retained his sense of awe about insects' evolutionary success over the millennia. "Insects won't inherit the Earth," he once said. "They own it now."