Of all the adult caddisflies the Grousewing sedge (Mystacides longicornis) is perhaps the easiest to identify. These small insects have long slender yellowish-brown wings, punctuated by three darker bands which, as its common name suggests, resembles a grouse feather. This caddisfly is found in all types of stillwaters, including lakes and ponds, as well as canals and slowflowing rivers. The larvae have particularly long hind legs, which they use for crawling in mud and sand on the bed or climbing among submerged vegetation. The Grousewing is one of the brown silverhorn sedges, so called because of their long white antennae, which extend to two and three times the length of their body. They also have distinctive large red eyes, which make them unmistakable as they rest on bankside vegetation. Grousewing larvae create a long slender, slightly curved case from sand grains, occasionally interspersed with bits of vegetation. Most caddis make a new case at each of their five moults but instead, the Grousewing merely adds an extension to its existing case. This results in the case tapering towards the rear. The adults emerge from the water surface during late afternoon and early evening, sometimes in huge numbers. These dense hatches can be spectacular with the air filled with dancing sedges. During the day they avoid the heat of the sun by resting in bankside vegetation, waiting until cooler conditions to restart their mating swarms. The males sweep back and forth over the surface of the water and the female enters the swarm where she is grabbed by a male and mating follows. Once mated the female
Long white antennae and banded wings.
will return to lay her eggs by dipping the end of her body in the water while skimming low across the surface.
Did you know?
The Grousewing is found throughout the country from Orkney to Cornwall.
Body: 6-9mm. Wing: 7-10mm. Flight period: June to September. Hatches: late afternoon and evening.