Dobsonflies have a soft, brownish body. They can grow up to 7 cm long. Two pairs of large wings of nearly equal length with rounded tips are fixed to the insect’s thorax. They are transparent, with spots. On its head are a pair of compound eyes, as well as simple eyes, or ocellae.
The order of Megaloptera includes some 300 species divided into two large families: Corydalidae (dobsonflies) and Sialidae (alderflies). There are 16 species of dobsonflies in Canada and at least five in Quebec. Among the 24 species of alderflies in North America, five are listed in Quebec, all belonging to the Sialis genus.
Megaloptera undergo a complete metamorphosis. The larvae, which are very different from adults, live in the water and are predatorial.
Dobsonfly larvae do not have the terminal filament at the base of their abdomen like alderfly larvae. They both breathe using tiny gills. Megaloptera larvae act as indicators of water quality, as they do not tolerate pollution well.
Dobsonfly and alderfly adults barely eat, although their jaws are strong and well adapted. Their imposing wings do not allow these insects to fly over long distances.