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Life in Freshwater

Alder Fly (Sialis lutaria)

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Alder Fly adult

The adult (20-25mm) may be confused with the lacewings but is a distinctive species and belong to a separate family, the Sialidae. The brown wings have dark, strongly defined veins. The head and thorax is thickly build and black. The larva is aquatic with a pair of pale gills coming from each segment. These gills are single strands unlike other aquatic larvae. There is a single strand coming from the end of the abdomen.

The Alder Fly is common throughout Europe where there still or slow moving water. The adults rest in the vegetation near ponds, streams and rivers. The larva lives at the bottom of these habitats, often under dead leaves or other vegetation

ECOLOGY: Like most Neuropterans both adult and larvae are carnivorous. The larva is aggressive and active with strong, curved jaws for catching and devouring the prey which consist of larval mayflies, fly larvae and other aquatic insects. A number of females will lay their eggs in large masses together. When the eggs hatch the mass emergence will increase the chances of survival as a predator will not be able to consume them all.

Alder Fly larva











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