Mosquitoes are insects in the family culicidae. They have a pair of scaled wings, a pair of halteres, a slender body, and long legs. The females of most mosquito species suck blood (hematophagy) from other animals, which has made them the most deadly disease vector known, killing millions of people over thousands of years and continuing to kill millions per year by the spread of infectious diseases.
Length varies but is rarely greater than 16 mm (0.6 inch), and weight up to 2.5 mg (0.04 grain). A mosquito can fly for 1 to 4 hours continuously at up to 1–2 km/h travelling up to 10 km in a night. Most species are nocturnal or crepuscular (dawn or dusk) feeders. During the heat of the day most mosquitoes rest in a cool place and wait for the evenings. They may still bite if disturbed.
Both male and female mosquitoes are nectar feeders, but the females of many species are also capable of hematophagy (drinking blood). Females do not require blood for their own survival, but they do need supplemental substances (like protein and iron) to develop eggs. Prior to and during blood feeding, they inject saliva into the bodies of their source(s) of blood. Female mosquitoes hunt their blood host by detecting carbon dioxide (CO2) and 1-Octen-3-ol from a distance. Mosquitoes of the genus toxorhynchites never drink blood.