Beyond a spider snacking on an unfortunate fly, the social lives of insects tend to go unrecognized. Perhaps you notice all the ants marching in a line, or bees heading back to a nest, but it all seems so mechanical, so primal.
In reality, insects have social lives that are more complex than you might imagine. One of the most intriguing is insect courtship. Across many species – such as crickets, fruit flies, moths – males must sing to the female in order to mate. The female will listen, considering, and if the male does well enough? Then he can mate. If he can’t sing well enough? He’s out.
While beautiful and touching, it does make you wonder why? Why should a female care that a male can sing well? There is evidence that song can indicate the fitness of the male – males with better song have offspring that are more likely to survive. However, insects often live in mixed environments that consist of many different species. If you dare, go to a garbage heap buzzing with flies. Chances are that it will have big ones and small ones, many different species competing for the same food. One way to screen out the wrong type of fly is to listen for the right song.
But insects are sneaky and can have alternative motives. Another use of the song lies not just in wooing a mate, but in scaring off competitors. Males of one species of moth will shout out a string of shrieks that sound like the ultrasonic homing call of the bat. Look at the figure below: while the long, crooning song used to attract females doesn’t scare off other males, bat calls – or the short pulse of other males – will send them packing (capture rate is the probability of a moth making its way to a trap emitting courtship pheromones).
Insects are tricky creatures, able to sneakily imitate predators in order to scare off competitors before deftly turning to romantic ballads.
Nakano, R., Ihara, F., Mishiro, K., Toyama, M., & Toda, S. (2014). Double meaning of courtship song in a moth Proceedings of the Royal Society B: Biological Sciences, 281 (1789), 20140840-20140840 DOI: 10.1098/rspb.2014.0840
Hoikkala, A., Aspi, J., & Suvanto, L. (1998). Male courtship song frequency as an indicator of male genetic quality in an insect species, Drosophila montana Proceedings of the Royal Society B: Biological Sciences, 265 (1395), 503-508 DOI: 10.1098/rspb.1998.0323
Photo by Johan J.Ingles-Le Nobel