Mosquito, any of 35 genera of small insects belonging to the fly order Diptera of the family Culicidae. Mosquitoes have long legs and 2 wings capable of beating about 1,000 times a second. Males survive on plant juices; females feed on the blood of mammals. They are able to pierce skin with needlelike parts in their proboscises. Certain species transmit diseases such as malaria, yellow fever, and encephalitis.