These aquatic insects are very similar to mosquitoes, but differ in having short mouthparts. Males and females do not bite. They are called phantom midges because of the pale to almost transparent larvae of the common Chaoborus species. Full-grown larvae are 9-12 mm long and nearly transparent except for black eyes and the pigmented hydrostatic organs on the enlarged prothorax and posterior end. The head has large and raptorial antennae that terminate in spines. The caudal segment has a ventral anal fan of setae (fin), a pair of ventral hooks, and anal gills. Larvae are predaceous on aquatic arthropods, and may kill a large number of mosquito larvae while feeding. Adults live only a short time, but may occur in large numbers on houses and other buildings after emerging from lakes, ponds, and reservoirs.

Clear Lake gnat, Chaoborus astictopus (= C. lacustris) Adults are 4-5 mm long with a brown body. Males have plumose antennae and a slender abdomen; antennae of females are not plumose, and their abdomen is enlarged. Adults appear in early May and occur in small to large numbers until mid-September. Adults can be numerous and create health problems in residential and resort areas. Eggs are deposited on the water surface, but sink to the bottom; hatching occurs in about 24 h. Larvae feed on plankton, mosquito larvae, and other animals in the water. Development takes 11-25 days; the pupal stage is 2-3 days. Larval stage 3 and 4 and the pupa remain in mud at the bottom ofthe habitat. Larval development is usually completed the following year. Adult emergence begins at about 23:00 h and extends to about 6:00 h. Adults spend 36-48 h resting on the ground or vegetation around the shoreline before laying eggs. This species is known from large numbers that occur along the shores of Clear Lake, in northern California.

Lake Nyasa gnat, Chaoborus edulis Adults are about 4 mm long with a dark brown body. Swarms of adults of this species occur over Lake Victoria and Lake Nyasa in East Africa, and they can appear as a black cloud, which moves with the wind. These swarms are a seasonal nuisance, and sometimes alarming and dangerous for people who may be sensitive to arthropod allergens. Fisherman in small boats may be covered and the breathing air filled with these midges. In the past, bodies of these midges were compressed into kungu cake and eaten by local people.

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