[3] Adult osmylids are small to moderately-sized net-winged insects, with wingspans ranging from 1.4 to 3 cm.

Adult osmylids, like green lacewings (some of which are colloquially known as "stinkflies"), have prothoracal glands which produce foul-smelling compounds used to deter would-be predators.

The body is elongated and slender and terminates in two extensible graspers bearing tiny hooks; these are used to aid in locomotion and to grasp prey.

The adults are diurnal or crepuscular weak-flying insects which mostly prey on small invertebrates, supplemented with some pollen.

The group also contains Archeosmylidae from the Permian-Triassic and Saucrosmylidae from the Middle Jurassic, both of which are thought to be closely related to Osmylidae.