Love at First Sniff: Male Moths Seek Females by Smell

Moths "sniff" out their ideal mate. Yet in the wild, there are an abundance of hybrid moths--something that shouldn't happen if males can sense females of the same strain. Now, though, researchers may have an explanation why these hybrid moths exist.

 Male moths use pheromones to find females. Pheromones are excreted chemicals that can trigger a social response in members of the same species. In the case of moths, the pheromone blends are specific for each species. Only males of the same species "understand" the volatile messages that the females send. Although moths can't successfully mate with other species, they can mate with other strains, which are different forms of the same species. That said, different strains seem to be singularly unattractive to male moths, which begs the question why there are so many hybrid moths found in the wild.

In order to better understand this process of attracting and selecting mates, researchers examined the European corn borer, a species in which males often mate with females from a different strain. During the course of the experiment, the researchers followed the flights of males to female pheromones in a wind tunnel. Since each strain of the European corn borer uses a blend of pheromone components in a very specific ratio, they expected the males to seek out females from the same strain.

Surprisingly, not all of the male moths chose female pheromones from the same strain. It turned out that, in fact, the male moths lost the ability to measure the ratio when it flew upwind along the pheromone plume. This, in turn, could explain why so many hybrids are seen in nature.

"Once male moths lock onto a pheromone plume, they are much less attuned to blend quality," said Teun Dekker, co-author of the study, in a press release. "In other words, males fly even to blends that were initially unattractive, and so can mate with females of different strains that they would not have approached otherwise, explaining why we find hybrid moths in nature."

The findings are published in the Proceedings of the National Academy of Sciences.