The Anopheles quadrimaculatus complex of 5 cryptic species (i.e., An. diluvialis Reinert, new species; An. inundatus Reinert, new species; An. maverlius Reinert, new species; An. quadrimaculatus Say; An. smaragdinus Reinert, new species) is analyzed using multiple techniques, including morphological, cytological, molecular, genetic, biochemical, and ecological procedures. All life stages (egg, 4th-instar larva, pupa, and female and male adults) are described using morphological features, and pertinent stages or structures are illustrated. A neotype for An. quadrimaculatus is designated, and the synonymy of An. annulimanus Van der Wulp is confirmed. Several new morphological features are described. New and summarized data from published literature on hybridization, cytological, electrophoretic, molecular, and cuticular hydrocarbon studies are included. Immature and adult bionomics are given. The geographic distribution for each species is listed and shown on maps. Procedures for collecting, processing, and rearing specimens are described. Keys using morphological characters are included for the eggs, 4th-instar larvae, pupae, adult females, and male genitalia. Also, a biochemical key for the 5 species is included. Color and pattern variations of larvae and pupae are discussed.