In April when the weather warms after the long winter we get millions of these flies swarming like balls of smoke along the lakeshore. Drifting in the wind they will land on brightly covered surfaces, usually the walls of a house, encouraging many people to keep their windows closed until ‘the plague’ is over. They rise to the water’s surface as pupae and struggle slowly through the surface film while the pupa’s body dangles vertically below. This is the most common stage for trout to take, though the adults may be useful at times too.

They appear again in September, though in lesser quantities,

Chironomidae (informally known as chironomids or nonbiting midges) are a family of nematoceran flies and many species superficially resemble mosquitoes, but they lack the wing scales and elongated mouthparts of the Culicidae.  Larvae of some species are bright red in color due to a haemoglobin analog; these are often known as “bloodworms”.