Mosquitoes are members of a group of almost 3,600 species of small flies within the family Culicidae. The word "mosquito" is Spanish and Portuguese for "little fly". Mosquitoes have a slender segmented body, one pair of wings, one pair of halteres, three pairs of long hair-like legs, and elongated mouthparts.

The mosquito life cycle consists of egg, larva, pupa, and adult stages. Eggs are laid on the water surface. The adult females of most species have tube-like mouthparts (called a proboscis) that can pierce the skin of a host and feed on blood, which contains protein and iron needed to produce eggs. Thousands of mosquito species feed on the blood of various hosts ⁠— vertebrates, including mammals, birds, reptiles, amphibians, and some fish.

The mosquito's saliva is transferred to the host during the bite, and can cause an itchy rash. In addition, many species can ingest pathogens while biting, and transmit them to future hosts.

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