Body length 20mm. A robust black insect that holds its four heavily veined wings tent-like over its abdomen. There are three very similar British species, distinguished by microscopic examination of the male genitalia. Sialis lutaria is the commonest and most widespread species.
The larvae develop beneath the water in lakes and rivers and the adults can be seen on waterside vegetation.
Status and distribution
Sialis lutaria is common and widespread in Britain. S. fuliginosa is widespread but local and S. nigripes is the least abundant species. S. lutaria is common and widespread in Nottinghamshire and at Netherfield Lagoons.
Best time to see
April to August.