Order
MEGALOPTERA(Greek, megas = large; pteron = wing)
Common Names
alderflies, dobsonflies, snakeflies
Description
The Order Megaloptera includes the snakeflies which some entomologists consider should be placed into the separate Order Raphidioptera. Still others are of the opinion that both these Orders should be placed within the Order Neuroptera. Megalopterans are soft-bodied insects with two pairs of delicate, large, finely veined wings. Often the wings are so long that they extend well beyond the abdomen. The antennae are long and composed of short, straight segments (filiform). The compound eyes are separate and well developed. Mandibles are prominent. The snakeflies are distinguished by having a "sit and wait" hunting technique similar to praying mantids, however the spiny forelegs are not present. Instead the head is very mobile and is shot forward (as in the head of a striking snake) so that the jaws can grasp the prey. Alderflies and dobsonflies have well developed mandibles, but do not feed in the adult stage.
Life Cycle
The life cycle is metamorphic: egg-larva-pupa-adult. All stages in snakeflies are terrestrial, but alderflies and dobsonflies have aquatic, gilled larvae called nymphs that prefer freshwater streams with clear, running water. The nymphs move over the floor of the stream and when mature pupate under rocks on the stream bed. Adults of some aquatic species take wing at or near dusk and fly about over the water surface.
Distribution
Megalopterans are best represented in temperate regions.
Food
Megalopterans feed on insects or other arthropods, whether aquatic or terrestrial. Both larval and adult snakeflies feed. However, adult alderflies and dobsonflies do not feed.
Importance
Megalopterans role as fish food in streams is extremely important. Alderflies and dobsonflies have larvae that are very intolerant of pollution and their presence in a stream is therefore a good indicator of its health.