Chaoboridae Phantom Midges

Adults are small (1.4—10 mm in length), mosquito-like midges without the elongate proboscis and abundant wing scales characteristic of the Culicidae (Fig. 8.1 OA). Eggs of members of the common genus Corethrella are laid on the surface of water and hatch within 2—4 days. The larval stage averages 15—32 days, and the pupa is active and lasts 3—6 days. The transparent larvae (Fig. 8.1 OB) are aquatic and are found commonly in lentic habitats (e.g., large lakes, small pools, bogs, small ponds). The larvae of all 19 species in the 5 North American genera are predators which grasp their prey with prehensile antennae. Prey include small crustaceans and aquatic insect larvae, including mosquitoes, which they sometimes eliminate from restricted habitats.

While most adults do not feed on blood, females of the genus Corethrella have toothed mandibles and have been found with avian and mammalian blood in their digestive tracts (Williams and Edman, 1968). Corethrella brakeleyi and C. wirthi have been observed feeding on tree frogs (Hyla spp.) (McKeever, 1977). Corethrella females are

Lake Entomology
FIGURE 8.10 Chaoboridae, the Clear Lake gnat (Chaoboms asticto-pus). (A) Adult female; (B) larva. (From Herms, 1937.)

attracted to the calls of male tree frogs (McKeever and French, 1991), to which C. wirthi can transmit a Trypanosoma species {Johnson et al.} 1993). They do not feed on female frogs, which do not call. The Clear Lake gnat (Chaoborus astictopus) is an inhabitant of large lakes and impoundments in the western United States. Large numbers emerge synchronously in the spring and are attracted to lights in residential and resort areas, where they can cause annoyance (Herms, 1937; Linquist and Deonier, 1942).

Generic keys for chaoborid larvae and adults are found in Cook (1981). Keys to United States species of Corethrella are found in Stone (1968).

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