With bloated bellies and hairy legs, female flies try to look bigger to get food from courting mates. But male flies, in turn, have sharpened their eyesight to call their bluff. A new study by researchers from the Universities of Gothenburg and Stockholm suggests that this is an ongoing evolution where both sexes try to outsmart each other.

With bloated bellies and hairy legs, female flies try to look bigger to get food from courting mates. But male flies, in turn, have sharpened their eyesight to call their bluff.