ITHACA, N.Y. -- An enduring nuptial gift is included in every sperm package from a male rattlebox moth (Utetheisa ornatrix)to his freshly mated female: a potent, plant-derived chemical that protects her for life against predatory spiders, biologists at Cornell University have discovered.
The first (but almost certainly, not the only) example of a sexually transmitted chemical defense to benefit a female animal is reported in the current (May 11, 1999) Proceedings of the National Academy of Sciences by Cornell biologists Andrés González, Carmen Rossini, Maria Eisner and Thomas Eisner. The protective chemical, pyrrolizidine alkaloids (PAs) that the adult male obtains by eating rattlebox plants (Crotalaria mucronata) while in the larval stage, reaches every part of the female's body within minutes after mating, the biologists say. It also protects her eggs.
"Only a human bridegroom would buy life insurance for his bride. This classy moth gives a gift she can really use -- a life assurance policy, if you will -- that keeps paying off every time her life is in danger," says Thomas Eisner, the Schurman Professor of Chemical Ecology at Cornell. During courtship, Eisner adds, the female rattlebox moth has a way of sensing which suitor offers the best chemical defense, and she chooses accordingly.
Native to central Florida, U. ornatrix earned another common name, the ornate moth, for its distinctive coloration, an intricate pattern of flamingo pink, black and white that adorns the inch-long adults. "They are one of the few moths to fly during daylight," Rossini says. "They literally flaunt their brilliant colors, as if to say: 'You should know from my pattern that I am distasteful.' "
Spiders that don't know the color code are quick to find out that the moth is
inedible. One taste of the chemical-laden moth is enough to make a spider cut
loose its erstwhile prey from the web, and the moth escapes unharmed. Th
Contact: Roger Segelken
Cornell University News Service