The family Culicidae, derived from culex, the Latin name for "gnat," is a member of one of the main stocks of Nematocera, the infraorder Culicomorpha. It consists of two superfamilies that include all of the piercing/ sucking nematocerans, both predators and blood-feeding biters. The superfamily Chironomoidea comprises the families Chironomidae and Thaumaleidae, which have nonpiercing mouthparts, and Simuliidae and Ceratopogonidae, which pierce either vertebrates or invertebrates. The superfamily Culicoidea comprises the Dixidae, Corethrellidae, Chaoboridae, and Culicidae, the second and fourth of which feed on vertebrate blood. Several of these families are superficially similar. However, among all the culicomorphs, the long proboscis of mosquitoes is distinctive. It is considered the most specialized of biting mouthparts among Nematocera and indicates a long and close association of mosquitoes with vertebrate animals. Wood and Borkent (1989) provide an overview of nematoceran phylogeny and classification.

Culicidae consists of about 3200 recognized species. The largest number remaining to be discovered probably inhabits tropical rain forests, where faunas are more diverse but less well surveyed than temperate regions. Species that have been studied intensively often reveal that they consist of complexes of closely related species, indicating that many reproductively isolated and niche-specific forms remain to be identified or are undergoing speciation. Current culicid classification (Table I) recognizes three subfamilies: Anophelinae, Culicinae, and

Toxorhynchitinae. Anophelinae and Toxorhynchitinae sometimes are considered to be primitive groups; other authorities view them as specialized derivations of some Culicinae-type ancestor. Recent cladistic analysis of morphological and nucleotide-sequence data supports the idea that the Anophelinae are only distantly related to the other two subfamilies and that the Toxorhynchitinae do not merit subfamily status (Harbach and Kitching, 1998). Anopheline eggs bear characteristic floats, their larvae lack air tubes, and adults have elongate palps in both sexes. Typical culicine and toxorhynchitine larvae have air tubes, and adult females have short palps. Toxo-rhynchitines are all predaceous as larvae, are unusually large, and have a curved proboscis suited for feeding on only nectar.

There are 38 genera of mosquitoes, 34 of which are in the subfamily Culicinae. Culicines are organized into 10 tribes, the most diverse of which are Aedini and Sabethini in terms of numbers of genera and species worldwide. The 14 genera in North America north of Mexico, and the number of species in each, are Anopheles (16), Aedes (7), Ochlerotatus (69), Psorophora (15), Haemagogus (1), Culex (29), Deinocerites (3), Culiseta (8), Coquillettidia (\), Mansonia(2), Orthopodomyia(3), Wyeomyia (4), Uranotaenia (4), and Toxorhynchites (1) (Darsie and Ward, 1981).

Three important species groups of mosquitoes worldwide are the Anopheles gambiae and Culex pipiens complexes and the Aedes subgenus Stegomyia. The An. gambiae complex of Africa consists of six species. Two of these, An. gambiae and An. arabiensis, are important vectors of malaria and lymphatic filariasis. An. arabiensis

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