Robber Fly (male) – 7/18/15

Observer: Paul Lauenstein

Observation Date: 7/18/15

Observation Time: 5:10 p.m.

Observation Location: Gavins Pond Dam

Common Name: Robber fly (male)

Scientific Name: Efferia apicalis

Comments: Robber flies of the genus Efferia are small to large-sized robber flies (10–40 mm) with a distinctly different shape of the posterior end of the abdomen in males versus females. Females have a short or long ovipositor that is hairless and short conical to slender wedge-shaped, its color is usually glossy black. Males (such as the one pictured below) have a “helicopter tail” with glossy black claspers that are covered in hairs, forming part of a complex genital structure (the combined epandrium and hypandrium) that is clearly larger than the abdominal segments and is oriented diagonally to vertically upwards relative to the main body axis.

As is typical for robber flies, adult Efferia are ambush predators, taking off from a resting position on the ground or on a branch to intercept other flying insects in mid-air.

More Information: Wikipedia