Alderfly

Any insect of the megalopteran family Sialidae, characterized by long, filamentous antennae and two pairs of large wings (anterior wing length 20 to 50 mm [ 3/4 inch to 2 inches]), membranous and well-developed, with part of the hind wing folding like a fan. The adult alderfly is dark-coloured, 15 to 30 mm ( 3/5 inch to 1 1/5 inches) long, sluggish, and a weak flier. It usually inhabits shore vegetation,