Owlflies (Haplogenius appendiculatus) can be found during the mid-summer twilight in most areas of North America. Contrary to the name, they are not true flies (Order Diptera), but belong to an order of carnivorous insects that have four net-veined wings and mouthparts adapted for chewing. Owlflies are closely related to lacewings and ant lions (note the similarities in wing structure on adults).

Owlflies, lacewings and ant lions are classified in the order Neuroptera which is a Greek name that reflects the nerve-like branching pattern of their wing veins. (The medical specialty of neurology has a similar meaning.)

Owlflies resemble a cross between a dragonfly and an ant lion. The difference is dragonflies have short bristlelike antennae and hold their wings outstretched while resting. The Owlfly sits with its body, legs and antennae compressed to a stem, and its abdomen is extended to the air resembling a broken twig.

Most Owlflies are about 2 inches in length. They have slender bodies with clear wings and a pair of very long “clubbed” antennae. Adult Owlflies have large, bulging, divided eyes, which is where the common name "Owlfly" comes from.

Owlfly males have prominent tufts of black bristles on top, near the base, of their slender abdomen. Female abdomens are plumper with diffused dark spots near the wing-tips, though sometimes these spots are absent or worn off. At rest, most species of Owlflies stick their abdomens in the air and wrap their wings downward around their perch.

Owlflies lay eggs, in clusters, at the tips of twigs and limbs. She then creates a protective silk-like cocoon a ¼ inch below the eggs, to prevent crawling predators from reaching them. This shield looks like a twisting spiral of evenly spaced, tiny, shiny rust-like stalks.

Hatched larvae stay together for a few days for protection purposes and live on small insects such as fruit files and midges that wander by the cluster. If touched by a predator, the larvae will lift their heads high and quickly snap their long sickle-shaped jaws.

Owlfly larvae usually separate from the group, descending to the ground in about a week. Once on the ground, they lead a solitary life. Unfortunately, little is known about what types of insects the larvae feed upon though it’s likely that any small, soft-bodied insects and other invertebrates that dwell in ground litter would likely be candidates. Pupation is known to occur in a silken cocoon in the litter.

Adult Owlflies are strong flying predators feeding on other insects. If disturbed, some adults release a strong, musk-like scent to deter an enemy.

While Owlflies may be viewed as having a bizarre appearance, they are one of many examples of insect predators that are seldom encountered but nevertheless aid us in controlling insect pests! If you happen to see one, please let it continue its way unharmed.

FIGURE 1. Contrary to their implied common name, Owlflies
are not true flies (Order Diptera), but rather belong to an
order of carnivorous insects that have four net-veined
wings and mouthparts adapted for chewing.