Wings are held either divergent or slightly upwards. The thoracic microchaetae are reduced in number and one or both postvertical bristles are almost always absent. There is a varying degree of abnormality in the shape of the head and eyes, from almost normal to extreme cases where the head is flattened anteroposteriorly and the eyes are deeply grooved. Males are viable and fertile, females are sterile.

Wings either divergent or slightly held up. Thoracic hairs sparse and one or both postvertical bristles almost invariably absent. Shape of head and eyes varies from almost normal to anteroposterior flattening of head and deep grooving of eyes. male viable male-fertile female-sterile. RK2.