Thomas Eisner, a groundbreaking authority on insects whose research revealed the complex chemistry that they use to repel predators, attract mates and protect their young, died on Friday at his home in Ithaca, N.Y. He was 81.

The cause was complications of Parkinson’s disease, said Cornell University, where he had been a professor of chemical ecology.

In the introduction to Dr. Eisner’s 2003 book “For Love of Insects,” the Harvard biologist E. O. Wilson called him “the modern Fabre,” after Jean-Henri Fabre, the French pioneer of insect research.

Dr. Eisner realized early in his career that in addition to sounds and visual cues like colored markings and elaborate dances, insects often communicate through chemical signals.