Ascalaphidae is a family of insects in the order Neuroptera, commonly called owlflies; there are some 450 extant species. They are fast-flying crepuscular or diurnal predators of other flying insects, and have large bulging eyes and strongly knobbed antennae. The larvae are ambush predators; some of them make use of self-decoration camouflage.
Owlflies are readily distinguished from the superficially similar dragonflies by their long, clubbed antennae; dragonflies have short, bristle-like antennae. The closely related antlions (family Myrmeleontidae) have short, weakly clubbed antennae, smaller eyes, and reticulate wing venation.[2][3] All but one species of Ascalaphidae have long antennae, easily distinguishing them. The sole exception is the Brazilian Albardia furcata, the only living member of the subfamily Albardiinae, which has short antennae, but these are strongly clubbed (compared to myrmeleontids), and its wing venation is reticulate, typical of ascalaphids. Most owlflies are about 1.5 inches (3.8 cm) in length, not including antennae.[4] Adult owlflies of the family Ululodinae such as Ululodes have large divided eyes and crepuscular habits, which is where the common name "owlfly" came from.[4] Owlflies are worldwide in distribution, occurring in warm temperate and tropical habitats; there are some 450 extant species.[5]
Adult owlflies are fast-flying, aerial predators, capturing and feeding on other insects in flight.[6] The larvae too are predatory, making owlflies important in maintaining a natural ecological balance and helping to control pest insects.[7]
Adults of many New World species are most active at sunset, and can often be collected near lights. During the day, adults rest on stems and twigs with the body, legs, and antennae typically pressed to the stem.[4] Some Old World species, such as Libelloides macaronius, are active during the day.[8]
When disturbed, some owlflies release a strong, musk-like chemical to deter enemies.[4] The abdomen in Ululodes quadrimaculatus is raised at rest, mimicking a broken twig.[4]
Some New World species such as Haploglenius luteus are able to suddenly reflex a flap on the pronotum, exposing a strongly-contrasting patch of pale colour (white or cream), either as a deimatic display to startle predators,[9] or as heliographic signalling, reflecting sunlight, to attract females.[10]