This family of about 1,000 species occurs throughout the world. Ten species are resident in the British Isles, an eleventh is almost certainly extinct and a twelfth is a suspected immigrant. Eggars are thickset, medium-sized or large moths with deep, rounded, usually warm brown or yellowish wings, generally bearing a small central spot or two cross-lines on the forewings.
The males have broadly feathered antennae with which they can detect the scent of unmated females from several hundred metres. The males of two of the largest British species (Oak Eggar and Fox moth) do this by day and are often seen flying rapidly on sunny afternoons. Females of these species and both sexes of others are nocturnal and come to light-traps. None are able to feed. Some species, such as the Oak Eggar, broadcast their eggs in flight, but most attach them to the foodplant. The larvae are covered in dense hairs, which protect them from being eaten by most birds, except cuckoos, and can sometimes cause skin irritation in humans when handled. Some feed openly by day and are often seen basking in the sun. Pupation occurs in a substantial, sometimes tough, cocoon formed above ground, attached to vegetation and generally incorporating some of the larval hairs. (Taken from Waring and Townsend’s Field Guide to the Moths of Great Britain and Ireland)