A Female Fly, Full of Fertilised Eggs, Is Swept by High

question 23

Multiple Choice

A female fly, full of fertilised eggs, is swept by high winds to an island far out to sea. She is the first fly to arrive on this island and the only fly to arrive in this way. Thousands of years later, her numerous offspring occupy the island, but none of them resembles her. There are, instead, several species, each of which eats only a certain type of food. None of the species can fly and their balancing organs (halteres) are now used in courtship displays. The male members of each species bear modified halteres that are unique in appearance to their species. Females bear vestigial halteres. The ranges of all of the daughter species overlap.
Which of these fly organs, as they exist in the description, best illustrates an exaptation?

• A) the vestigial halteres
• B) the halteres
• C) the mouthparts
• D) the eggs

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