[2] Sialinae have a body length of less than 25 mm (1 inch), long filamentous antennae, and four large dark wings of which the anterior pair is slightly longer than the posterior.

When the larvae are born they drop into the water or the ground nearby it and make their way into their new aquatic biome.

The larvae are aquatic, active, armed with strong sharp mandibles, and breathe by means of seven pairs of abdominal branchial filaments.

When full sized, which takes between one and two years, they leave the water and spend a quiescent pupal stage on the land before metamorphosis into the sexually mature insect.

[4] Family Sialidae Sialis lutaria is the commonest alderfly in the United Kingdom[5] and across much of Europe.