Male fragrance attracts moth mates.

Male fragrance attracts moth mates

Two years ago, entomologist Peter J. Landolt noticed something strange about the mating behavior of the cabbage looper moth, Trichoplusia ni. The caged insects hung upside down, vibrated their wings, raised their abdomens and partially exposed their genitalia in the familiar stance associated with the release of sex pheromone -- a perfume irresistible to loopers of the opposite sex. Many female moths, including cabbage loopers, secrete such chemical lures.

But in this case the pheromone producers were males.

Landolt and chemist Robert R. Heath at the USDA's Insect Attractants, Behavior and Basic Biology Research laboratory in Gainsville, Fla., have now isolated and identified a sec pheromone produced by male cabbage loopers -- the first dirct evidence, they say, that male moths of any species secrete a scented lure to announce their presence to potential mates.

Landolt and Heath say the finding suggests a better moth trap for limiting populations of this pest, whose larvae devour the leaves of cabbage, broccoli and other cruciferous vegetables. The discovery also highlights the male looper's unusual role in the insect mating game, the scientists note in the Aug. 31 SCIENCE.

Female cabbage loopers seek out males for breeding -- a reversal of standard sex roles among insects, says Landolt. The females must also scout for suitable egg-laying sites. In the laboratory, Landolt and Heath found that male loopers often mark plants appropriate for egg-laying with a telltale pheromone scent. thus, female cabbage loopers hit the jackpot when they follow their noses, finding both home and hubby with a minimal expenditure of time and energy.

Landolt calls sexual communication among looper moths "a two-way street" that likely evolved to ensure successful mating. The male pheromone consists of a mixture of a rare form of linalool--a sweet-smelling oil otherwise found only in coriander seeds--and cresols, a component of a coal tar. Female loopers emit a chemically distinct male-attracting odor, the researchers find.

Males far outnumber females in this species, and efforts to reduce cabbage looper populations by luring males to traps sprayed with female sex pheromone have proved ineffective, leaving a large percentage of males still available for mating. Landolt and Heath suggest that traps baited with the newly isolated male pheromone may work better by targeting the smaller population of females.