Moths won't mate without oak leaves.

Two Harvard biologists have found that when the female polyphemus moth, receives the vapor from the oak through its antennae, it releases a chemical--a sex pheromone--which activates the male.

"No one has ever found or looked for a similar system where a plant is necessary to turn on an animal," Dr. Lynn M. Riddiford, assistant professor of Biology, said yesterday. She and Carroll M. Williams '46, Bussey Professor of Biology, have been investigating the sex life of the moth since last March.

Only Oak

"Oak is the only plant which activates sexual activity." Dr. Riddiford said.

The pair made the discovery several months ago when Dr. Riddiford needed moth eggs, and learned that they had never been produced in the laboratory. She found that although males usually are attracted to female moths from as far away as two miles, they failed to mate when caged together in the laboratory.

Unwilling to wait until spring, when the moths could be mated outside, Dr. Riddiford placed the moths in a cage with oak seedlings. These moths and a pair in a nearby cage mated.

The experiment, reported in the February 3 issue of Science, was prompted by previous research in which the moths that wouldn't mate in the laboratory mated in cages hung in trees.

But Dr. Riddiford and Williams repeated the experiment with a variety of trees and found that in all except oak, no mating occurred.

The biology team next plans to trace the reaction which causes the oak vapor to activate the female. They will remove certain endocrine glands to see if the moths will still mate without these glands.