Remember your college days? On a typical college Saturday night, I would head to a local Champaign, IL watering hole and get to “observe” the mating rituals of college men. Chest puffing, feats of strength, and sometimes even fisticuffs were employed to gain the favor of a particular lady. Turns out this male-male aggression is a trait we share with the little fruit fly. Those little fruit flies have, in turn, shown us that male-male aggression can be a bit more complex than we might first expect.
A new study in Nature Neuroscience has revealed that it’s not just simple aggression between multiple males whenever a female is present. If a male fruit fly has previously interacted with a female fruit fly (even if they don’t mate), it will be less aggressive toward another male fly that is introduced into the mix. This effect requires that the male and female flies have made physical contact with each other. This effect doesn’t last forever, just ~2 days; but it’s interesting that there is a specific male receptor for female pheromones inhibits aggression. What is the evolutionary advantage of this particular effect?
Is this a way to balance the drive for reproduction with the ability of the individual to survive? Are anthropomorphized, male fruit flies saying to themselves, “Hey, I’ve been around this fine lady all week. I like my odds. No need to risk my life fighting all these other dudes. Just be cool.”?
Do you have any alternate theories why something like this might happen?
The Finch and Pea 
The male fly is avoiding the embarrassment of having the new acquaintance tell everyone she knows what crazy things her new friend did at the watering hole on Saturday night.