Cicada mating calls attract friend - and foe

"Every summer, the grasslands of the central Great Plains ring with the mating calls of male cicadas that are trying to attract female cicadas," says Brian Stucky, an insect biologist at the University of Colorado.

What they also attract, Stucky found, is a fly species known as Emblemasoma erro.

Unwelcome attention

Seeking a host for the next generation, the female fly hones in on the cicadas' chirping. It deposits larvae on the cicada, which kills the insect by eating it from the inside, leaving nothing but a husk in the end.

But male flies and female flies without eggs that are ready to mate are also attracted by the cicadas' calls because that's where the action is, Stucky explains in an article in the Journal of Insect Science, which is published by the Entomological Society of America (EMA).

"It's as if the cicada is a singles bar, and its music is a Barry White CD," Stucky says.

Keen hearing

Using a loudspeaker mounted on a wooden box, Stucky broadcast cicada calls at different sites in a field study from 2011 to 2013. He caught the flies that were lured in by the calls and counted them. It turned out both sexes were attracted, even females that were not carrying larvae. About three out of four flies he caught were female.

"Hearing is a multi-functional sense in insects," Stucky concludes, arguing that hearing may well have originated as a means of finding a host where the flies are concerned, but it's "become useful in another way as well."