What is a key distinguishing feature of flies compared to other flying insects?

Flies are primarily characterized by having two wings, which is a notable feature that sets them apart from many other flying insects. In the order Diptera, which includes all true flies, the adult form possesses a single pair of functional wings for flight. The second pair of wings has evolved into small structures called halteres, which are used for balance and stabilization during flight. This adaptation is unique to flies and allows them to perform agile maneuvers in the air.

Other flying insects, such as bees and butterflies, typically have four wings. The presence of wings in pairs, with both pairs functioning for flight, is common among many insect orders. Regarding larvae, flies, or maggots, do not possess legs in the same way that many other insect larvae do. Most fly larvae lack legs entirely, which further distinguishes them from larvae of other insects that might have six legs or multiple prolegs. This combination of features highlights the specific evolutionary traits of flies within the vast diversity of the insect world.