How Interacting With Females Increases Aggression in Male Fruit Flies
by Lori Dajose, California Institute of Technology / Dec. 12, 2019 / phys.org

Caltech researchers have now made progress toward understanding the neurological basis of the heightened aggression that male Drosophila show toward one another after recent encounters with females.

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When a male fly encounters a female fly, the male often will vibrate his wings in a display of courtship. It is well-established that certain neurons, called P1, are responsible for this predictable courtship behavior and are activated by female scent cues. Once the female is removed from the male’s environment, the male’s P1 neurons become inactive.

But something about a prior experience with a female causes a male fly to enter into a state of heightened aggressiveness, or arousal, that lingers for a few minutes after the female is gone. Normally, two male flies can coexist in the same area without bothering each other. But male flies who have recently encountered a female will, when encountering another male, show increased displays of aggression: they lunge forward, waving their wings to look larger.

Stupid flies. You’d never catch humans exhibiting this kind of behavior at a bar or dance club!