When the dust has settled, the largest-stalked males are generally the ones who’ve earned the right to mate, passing along their big-eyed genes and ensuring that their name-sake trait continues.
When choosing a mate, the females within a rather unique family of flies make their decision depending on whether the eyes have it or not.
No. We’re not talking about the “ayes have it” -- counting the number of “yes” or “no” votes a particular male receives. We’re literally talking about the eyes – the visual organs.
For stalk-eyed flies, beauty is definitely in the eye of the beholder …or more accurately in how far apart those eyes are spread.
As you might guess from their name, male stalk-eyed flies have “eyestalks”, or projections from the sides of their heads, with their eyes at the end. They sort of look like the hammerhead sharks of the insect world, but even more bizarre in appearance.
Thanks to the females’ preference for suitors with the widest gap between their eyes …over time, sexual selection has pushed the males to ocular extremes.
When vying for a prime territory and the attention of the ladies, a group of males will compete amongst each other to determine who truly is the lord of the flies. Rivals will face off and size one another up. When the difference in eyestalk length is obvious, the smaller stalked males plead no contest.
But when males with similarly impressive peeper stems meet, they don’t hesitate to engage. When appearance is not enough to settle the score, these fights can become physical. Males will resort to head butting each other or even throwing punches using their first pair of legs.