Sisyridae (Spongeflies) Identification

In the British Isles there are three species of Sisyridae all in the genus Sisyra:

Sisyra nigra, Sisyra terminalis, and Sisyra dalii

Occassionally, there can be confusion between the family Hemerobiidae (Brown Lacewings) and Sisyridae, as they superficially resemble each other. If you look at the forewings it is relativley easy to differentiate between these two families. Hemerobiidae only have two longitudinal veins in the the top half of their forewing, whereas Sisyridae have three (see image below).

Difference between Hemerobiidae and Sisyridae – Images by T. Rintala & T. Lehto: Hemerobiidae, Sisyridae (both CC BY-4.0)

It is possible to identify these species from good quality photographs, where the wing and antennae are in focus (see below).

ID features for Sisyra species – Images by O. Fogh Nielsen (CC BY-4.0)

However, it is very easy to differentiate between the species by looking at the male genitalia:

Male and female genitalia of the British Isles Sisyra species. Images: CBG Photography Group: S. nigra and S. terminalis (both CC BY-3.0)