An Introduction to Megaloptera: the Alderflies
A small order of insects, worldwide there are around 380 species of alderfly in 2 families. In Britain there are 3 species in 1 family. Megaloptera is an order of insects commonly known as alderflies, dobsonflies, and fishflies. These insects are characterized by their large, elongated bodies, membranous wings, and aquatic larval stages
The larvae of Megaloptera, known as hellgrammites or fishfly larvae, are aquatic and typically inhabit freshwater streams, rivers, and lakes. They are voracious predators, feeding on small aquatic invertebrates, fish eggs, and even small fish. Hellgrammites have elongated bodies with well-developed jaws, allowing them to capture and consume prey effectively.
The adults of Megaloptera are terrestrial and are often observed near freshwater habitats, particularly in wooded areas. They have large, membranous wings and long antennae, giving them a somewhat delicate appearance despite their robust bodies. Adult alderflies, dobsonflies, and fishflies are relatively short-lived, with their primary focus being reproduction.
Reproduction in Megaloptera typically involves elaborate courtship rituals, with males engaging in displays of flight and pheromone release to attract females. After mating, females deposit their eggs on vegetation or directly into the water, where they hatch into aquatic larvae. The larvae undergo several molts before pupating and emerging as adults.
Megaloptera species play important roles in freshwater ecosystems as both predators and prey, contributing to nutrient cycling and serving as indicators of environmental quality. They are sensitive to water pollution and habitat degradation, making them valuable bioindicators of ecosystem health.
Identification of species relies on microscopic examination of the genitalia in males and the anal plates in females. Wing venation is very variable and should not be used as a means to identify species.
Classification
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Animalia (Animals)
Arthropoda (Arthropods)
Hexapoda (Hexapods)
Insecta (Insects)
Pterygota (Winged insects)
Neoptera
Endopterygota (also known as Holometabola)
Megaloptera (Alderflies)
Family Sialidae
All photographs copyright © Peter Hillman
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