Alderflies are aquatic insects where the larvae are predators of other invertebrates. The adults are usually found at rest near slow-moving water bodies such as ponds, canals and streams, usually on nearby vegetation or man-made structures, and with their wings folded in a tent-like fashion.
There are 3 species found in Britain. 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.