Sialis lutaria

This species is common in Norfolk, often found during the day-time near water between April and early June. I have also found them at night by torchlight, but never attracted to light.

Aldeflies cannot normally be identified from photos and it would be very difficult to see the relevant characters when examining a live specimen. Males need a look at the abdomen from the side and females need a look at the adomen from below. Details of how to identify them can be found in the FSC Aidgap key to lacewings and their allies by Colin Plant (1997).

Most of the insects I have found have been males, and these are reasonably easy to identify with a fresh specimen. If it has dried out then it may be necessary to macerate the abdomen, for example in potassium hydroxide solution, before the critical details are visible. Females need a good look at the underside of the abdomen. The only female alderfly I have found so far was in the jaws of a centipede and unfortunately the bit of the abdomen that is required for identification had already been eaten.

male Sialis lutaria showing end of abdomen, Wendling Beck Environment Project (Norfolk, UK), 15th April 2024

All of the following alderflies were examined, including those first photographed in the field.

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 8th April 2019

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 15th May 2019

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 27th May 2021

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 16th May 2021

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 21st April 2019

male Sialis lutaria, Wendling Beck Environment Project (Norfolk, UK), 26th May 2023

male Sialis lutaria, Wendling Beck Environment Project (Norfolk, UK), 29th April 2023

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 24th April 2020

male Sialis lutaria, Costessey (Norfolk, UK), 28th May 2016

male Sialis lutaria, North Elmham Cathedral Meadows (Norfolk, UK), 20th May 2021

2x male Sialis lutaria, Wendling Beck Environment Project (Norfolk, UK), 14th May 2022

2x male Sialis lutaria, Wendling Beck Environment Project (Norfolk, UK), 16th April 2022

male Sialis lutaria, Wendling Beck Environment Project (Norfolk, UK), 26th April 2022