When two male stalk-eyed fly opponents face one another head-to-head in a threat display, one usually retreats without a fight. The one that retreated did so because
A) he has longer eyestalks than his opponent.
B) he has shorter eyestalks than his opponent.
C) his opponent was able to detect that he was faking longer eyestalks than he actually has.
D) any of the above is likely.

Question

Quizplus · Accepted Answer

In stalk-eyed flies, males with longer eyestalks are generally more dominant and likely to win contests. Therefore, a male with shorter eyestalks is more likely to retreat when facing a male with longer eyestalks.

When Two Male Stalk-Eyed Fly Opponents Face One Another Head-To-Head