Stalk-eyed Fly - Morphology

Morphology

The Diopsidae are small to medium-sized flies, ranging from about 4.0 to about 12.0 millimeters in length. Their heads are subtriangular, with variably produced transverse eye stalks in all genera except the African genus Centrioncus. The head is usually sparsely haired, with vibrissae (whiskers) absent.

The posterior portion of the fly's metathorax, or scutellum, has a pair of stout processes, and often the laterotergite (one of a number of lateral flanges) of the postnotum (a small dorsal sclerite on the insect thorax posterior to the notum) has a dome-like swelling or spine-like process. The anterior femora of the legs are stout, with ventral spines. Adult males have lost tergites seven and eight, and the seventh sternite forms a complete ventral band.

Stalk-eyed flies, as the name implies, typically possess eyestalks. Their eyes are mounted on projections from the sides of the head, and the antennae are located on the eyestalks, unlike stalk-eyed flies from other families. A rather remarkable feature of stalk-eyed flies is their ability, shortly after they emerge from their pupae, to ingest air through their oral cavity and pump it through ducts in the head to the tips of the eye stalks, thereby elongating them while they are still soft and transparent.