What are mosquitoes? Mosquitoes are delicate, long-legged two-winged flies (order Diptera, family Culicidae) that are easily recognized by their long proboscis and the scaly wings and legs (Figure 1). More than 3,500 species inhabit the temperate and tropical regions of the world. Females of many species suck blood — all males and many other females feed exclusively on nectar, fruit juices and plant exudates. Blood-sucking females require blood for egg development. Warm-blooded animals are a common source of blood, but many mosquito species also attack cold-blooded animals such as snakes, turtles, toads, frogs and other insects. Some species are active at night or twilight while others are active during the daytime.