Holometabolous insects with 1 pair of functional wings, second pair reduced to tiny knobs called halteres which function as gyroscopes when the insect is in flight. The most important group of biting and disease transmitting insects.
Adults have many-segmented, filiform antennae.
Only the adult females bite. Adulst with 3-5 segmented antennae, third segment usually not aristate. Only the adult females bite.