Megaloptera (Alderflies) Identification

There are three species of megalopteran in the British Isles: Sialis lutaria, Sialis fuliginosa, and Sialis nigripes. These species can only be identified from examining their genitalia, the identification features are shown below for both Male and Female specimens.

Identification features for Sialis species. Males are viewed from the side and Females from underneath. Image top right: T. Rintala & T. Lehto (CC BY 4.0)