Evolutionary biologists view mosquitoes as micropredators, small animals that parasitise larger ones by drinking their blood without immediately killing them.

Medical parasitologists view mosquitoes instead as vectors of disease, carrying protozoan parasites or bacterial or viral pathogens from one host to another.

Eggs are laid on the water surface; they hatch into motile larvae that feed on aquatic algae and organic material.

[14] Females can live for up to three weeks in the wild, depending on temperature, humidity, their ability to obtain a blood meal, and avoiding being killed by their vertebrate hosts.

[14][17] The eggs of most mosquitoes are laid in stagnant water, which may be a pond, a marsh, a temporary puddle, a water-filled hole in a tree, or the water-trapping leaf axils of a bromeliad.

[19] The mosquito larva's head has prominent mouth brushes used for feeding, a large thorax with no legs, and a segmented abdomen.

For example, Culiseta melanura sucks the blood of passerine birds, but as mosquito numbers rise they attack mammals including horses and humans, causing epidemics of Eastern equine encephalitis virus in North America.

[37] Mosquitoes prefer to feed on people with type O blood, an abundance of skin bacteria, high body heat, and pregnant women.

Body odour, composed of volatile organic compounds emitted from the skin of humans, is the most important cue used by mosquitoes.

However, the malaria mosquito Anopheles gambiae also has OR4 genes strongly activated by sulcatone, yet none of them are closely related to AaegOr4, suggesting that the two species have evolved to specialise in biting humans independently.

[45] Externally, the most obvious feeding structure of the mosquito is the proboscis, composed of the labium, U-shaped in section like a rain gutter, which sheaths a bundle (fascicle) of six piercing mouthparts or stylets.

The labium bends back into a bow when the mosquito begins to bite, staying in contact with the skin and guiding the stylets downwards.

[62] Upon completion of feeding, the mosquito withdraws her proboscis, and as the gut fills up, the stomach lining secretes a peritrophic membrane that surrounds the blood.

[68][69] Many can tolerate subzero temperatures, while adults of some species can survive winter by sheltering in microhabitats such as buildings or hollow trees.

During that time, though, they emerge in huge numbers in some regions; a swarm may take up to 300 ml of blood per day from each animal in a caribou herd.

[73] El Niño affects the location and number of outbreaks in East Africa, Latin America, Southeast Asia and India.

The vector, the Asian tiger mosquito Aedes albopictus, has by 2023 established across southern Europe and as far north as much of northern France, Belgium, Holland, and both Kent and West London in England.

Among the many aquatic insects that catch mosquito larvae are dragonfly and damselfly nymphs, whirligig beetles, and water striders.

[80] Mosquitoes are parasitised by hydrachnid mites, ciliates such as Glaucoma, microsporidians such as Thelania, and fungi including species of Saprolegniaceae and Entomophthoraceae.

[80] Several flowers including members of the Asteraceae, Rosaceae and Orchidaceae are pollinated by mosquitoes, which visit to obtain sugar-rich nectar.

[83] A 2023 study suggested that Libanoculex intermedius found in Lebanese amber, dating to the Barremian age of the Early Cretaceous, around 125 million years ago was the oldest known mosquito.

Burmaculex antiquus and Priscoculex burmanicus are known from Burmese amber from Myanmar, which dates to the earliest part of the Cenomanian age of the Late Cretaceous, around 99 million years ago.

[87][88] Paleoculicis minutus, is known from Canadian amber from Alberta, Canada, which dates to the Campanian age of the Late Cretaceous, around 79 million years ago.

[89] P. burmanicus has been assigned to the Anophelinae, indicating that the split between this subfamily and the Culicinae took place over 99 million years ago.

[88] Molecular estimates suggest that this split occurred 197.5 million years ago, during the Early Jurassic, but that major diversification did not take place until the Cretaceous.

"[94] Mosquitoes are members of a family of the true flies (order Diptera): the Culicidae (from the Latin culex, genitive culicis, meaning "midge" or "gnat").

[112] Genetic modification methods including cytoplasmic incompatibility, chromosomal translocations, sex distortion and gene replacement, solutions seen as inexpensive and not subject to vector resistance, have been explored.

Other myths from the Yakuts, Goldes (Nanai people), and Samoyed have the insect arising from the ashes or fragments of some giant creature or demon.

Similar tales found in Native North American myth, with the mosquito arising from the ashes of a man-eater, suggest a common origin.

[131] Lafcadio Hearn tells that in Japan, mosquitoes are seen as reincarnations of the dead, condemned by the errors of their former lives to the condition of Jiki-ketsu-gaki, or "blood-drinking pretas".