Hormone triggers moth mating.

Hormone triggers moth mating

Studies have shown that most female moths looking for mates release a self-manufactured perfume, or sex pheromone, as soon as they emerge from the cocoon. Now scientists have found a moth, the true armyworm, that waits to mate until weather permits, thereby controlling the release of the sexy substance with a chemical system.

Canadian biologists Michel Cusson and Jeremy N. McNeil of Universite Laval in Sainte-Foy, Quebec, wanted to know if the same chemical, called juvenile hormone, that controls migration and ovary development in many insects might be responsible for the armyworm moth's release of pheromone and the behavior patterns, termed "calling," associated with this release. The researchers removed the corpus allatum, the source of juvenile hormone, from newly emerged, female armyworm moths and compared these to their normal counterparts as well as to armyworm moths that underwent a sham operation. Within five days, most of the controls and sham-operated moths "called," produced pheromone and developed mature ovaries, but none of the "allatectomized" moths did.

However, the researchers restored all three of these traits in the organ-deficient moths by injecting juvenile hormone.

The armyworm moth findings support a decades-old hypothesis that hormonal control over pheromone release should evolve only in long-lived adult insects that suppress mating during certain times. Environmental cues probably prevent the armyworm moth from making large amounts of juvenile hormone and pheromone in the spring or fall, when the species usually migrates, the researchers write in the Jan. 13 SCIENCE.

Cusson and McNeil propose that juvenile hormone acts directly on the central nervous system, which responds by producing a protein molecule that initiates pheromone production and creates neural messages that tell the insect to start "calling."