The double Para midge pattern is one that mimics the adult midges that often cluster together in groups on the surface of the water. Trout often target these clusters in order to get enough to eat.
Midge, (family Chironomidae), also called chironomid, nonbiting midge, or gnat, any of a group of tiny two-winged flies (order Diptera) that superficially resemble mosquitoes. Although they resemble mosquitoes, midges are harmless, with small mouthparts that are not elongated into a piercing structure for blood feeding. They do not have scales on wings or body, and the pattern of wing veins differs from that of mosquitoes. The male antennae are feathery.
Midges are usually found around ponds or streams in late afternoon and evening in swarms that produce a humming sound. Midges may breed in water or manure or under tree bark.