Owlflies are dragonfly-like insects with large bulging eyes and long knobbed antennae. They are not true flies, but rather neuropterans in the family Ascalaphidae, and as such are not closely related to the true flies at all; to the dragonflies and damselflies, they are even more distantly related.
Owlflies are readily distinguished from dragonflies because the latter have short bristle-like antennae. The closely related ant-lions, family Myrmeleontidae, have short, clubbed antennae, smaller eyes, and very different wing venation. The sole living member of the subfamily Albardiinae, the Brazilian Albardia furcata, also has short, clubbed antennae, but its typical reticulate ascalaphid wing venation demonstrates its actual relationships.
Adult owlflies are aerial predators feeding on other insects. When disturbed, some owlflies will release a strong, musk-like, chemical to deter an enemy. Adults of many New World species are most active at sunset and dawn and can often be collected around lights. During the day, such adults rest on stems and twigs with the body, legs, and antennae pressed to the stem. The abdomen in a few species is held up, projecting into the air, to look like a broken twig. Many Old World species, however, are most active during the day, and are brightly colored - many even hold their wings spread at rest like dragonflies; perhaps this is a form of mimicry to benefit from the fact that dragonflies are aggressive predators which smaller predatory insects (for which the average neuropteran would be prey) would better avoid. Most owlflies average about 2 inches in length. Adult Ululodes have large divided eyes, which is where the common name "Owlfly" came from, in addition to their crepuscular habits. Owlflies are worldwide in distribution, though in North America they are primarily southerly.
Eggs are laid on twigs or under stones. Larvae are predatory, and lie on the ground or in vegetation, covered with debris, waiting for prey. Larvae resemble those of ant-lions, but have a "finger-like appendage" on the side of each segment. Some genera actively cement sand and debris onto their bodies as camouflage. Pupation occurs in a spheroidal silk cocoon in leaf litter.
On the other hand, the owlflies are an ancient group, dating back to the mid-Mesozoic at least. A number of fossil owlflies and owlfly larvae have been found, often encased in amber. Most of these also cannot be placed in a particular subfamily. Most are known from the Oligocene; the Late Jurassic Mesascalaphus may be an entirely more basal member of the family. Fossil owlfly genera incertae sedis include:
Cratopteryx is probably a member of the Myrmeleontoidea and being of Early Cretaceous age would possibly belong in some named family of these. Sometimes assigned to the Ascalaphidae, it is better considered incertae sedis however.