Alder Fly - Sialis lutaria

Alder Flies are dark brown with greyish-brown wings with black veins.

There are three very similar Sialis species in Britain and detailed examination is required for species identification. When submitting a record for Sialis species please mention the details that you have used to help you to determine the species.  Any records without this information can only be accepted as 'Plausible'.  In order to distinguish the three species of Sialis, examination of the external genitalia (males) or anal plates (females) is required, but is relatively easy as no dissection is required.

It can be found near ponds and streams with silted bottoms and an abundance of weed or plant detritus. Despite its name, it has no association with Alder trees, other than being found on foliage beside water, which is where Alder is usually found.

Adults can be seen resting on emergent vegetation around the pond, mainly in May and June, often in large numbers.

It lays its eggs in large batches of 200 or more on plants or other objects at the water's edge. The larvae are aquatic, living amongst mud and detritus and preying on smaller insects.

Very common and widespread in Britain.

Common in Leicestershire and Rutland.