For gentlemen fruit flies in search of a mate, beauty is in the legs of the beholder. Because male Drosophila have a sensory system that keeps them from courting flies of a different species. And it’s located in their forelegs. The finding is in the journal Cell. [Pu Fan et al., Genetic and Neural Mechanisms that Inhibit Drosophila from Mating with Other Species]

When a boy fly approaches a potential partner, he taps her repeatedly on the side with those forelegs. But he’s not just being a pest. Turns out he’s checking her out at a molecular level.

On his legs are sensory neurons equipped with a taste receptor called Gr32a. The receptor samples the waxy chemicals on the skin of his love interest. If the flavor is that of another species, Gr32a is turned on and the fly high-tails it out of there.

When researchers removed the males’ sensory appendages, or simply disarmed Gr32a, the airborne Romeos tried to mate with any female on six legs. They even went for species that were three times larger than themselves, a relationship that even an untrained human eye can see is out of balance.

The system presumably keeps male flies from wasting their time pursuing females with whom coupling would prove less than fruitful.

—Karen Hopkin 

[The above text is a transcript of this podcast.]