Mud Alderfly

Sialis lutaria

One of three UK species which can only be readily identified by genital examination. It has dark brown, smokey coloured wings with thick, black veins. They are folded over the body of the insect like at tent when it is at rest. The adults are very weak fliers. Body length 10-15mm.

Mud Alderfly (Sialis lutaria)

The larvae breed in the mud or silt at the bottom of still or slow-moving water bodies like ponds, streams and canals. The female lays up to 200 eggs on plants overhanging the pond, and when they hatch the tiny larvae drop into the water or onto the ground and then crawl into the water. The adult life of alderflies is short. They live for just a week or two from the time they emerge in late April to the end of June. By contrast the larvae live underwater for up to 2 years. The larvae are carnivorous feeding on other invertebrates.

Flies April to October. Found in all types of freshwater environments. The adults are often found resting on vegetation near water. The commonest of the three species of alderfly found in the UK. They are widespread throughout.

Photograph taken May 2015, local canal, Staffordshire. When I first saw this alderfly resting in the sun atop an old canal bridge coping, I thought it was a caddisfly. This is my first photograph of an alderfly, and indeed my first sighting of one, so I guess I could be forgiven for my error.