Female moths join pheromone choruses.

Females of the species called rattlebox moths sniff out each other's male-attracting pheromones and congregate, creating the pheromone-based equivalent of male frogs gathering in a pond to croak a mating chorus, say researchers.

The rattlebox moth (Utethesia ornatrix) became famous when researchers figured out how the species uses and depends on plant toxins. The moths pick up alkaloids from several wild legumes in the Crotalaria genus. Males offer their prospective mates sperm packages dosed with these alkaloids. The females take the alkaloids and incorporate them into their eggs, protecting them from predators that are repelled by the chemicals.

As in many moths, U. ornatrix females attract males by pumping out pheromones. In the last few years, Hangkyo Lim and Michael Greenfield of the University of Kansas in Lawrence have found that female rattlebox moths not only detect the sexy scents from other females but also respond by releasing their own pheromones more abundantly.

Lim and Greenfield are also exploring whether female moths are attracted to other females' pheromones. When the researchers put a female in a Y-shaped passageway, she tended to go into the arm filled with the stronger pheromone concentration.

For an outdoor test, Lim set out cages of scent-releasing females in patches of Crotalaria in Florida and recorded the number of females that alighted nearby to mate. In 2 nights of observation, he found more mating females near caged moths than near empty cages. He also found that the moths congregated only on the downwind side of the occupied cages, further evidence that the females' scent was attracting females. He proposes that these female moths cluster and intensify their signals in a chorus that advertises for males.