Mosquito

 Mosquitoes are small flying insects belonging to the family Culicidae, which contains roughly 3,600 species. The name comes from the Spanish and Portuguese word for "little fly." Every mosquito drinks sugary plant fluids, but the females of many species have taken on something far more notorious: blood. That single habit makes them the deadliest animals on Earth, responsible for well over a million human deaths every year through the diseases they carry.

What they look like

A mosquito is built like most flies — one pair of wings, six long thin legs, a slender body usually grey or black, and about 3 to 6 millimetres long. Their wings are narrow and covered in tiny scales. The standout feature is the proboscis, a needle-like mouthpart made for piercing skin and sucking fluid. Males, who never bite, have simpler mouthparts suited to sipping nectar. When resting, mosquitoes hold their front legs stretched outward, a small detail that distinguishes them from harmless midges that look otherwise similar^[1].

Size varies widely by genus. The largest, Toxorhynchites, can reach 18 millimetles in length with a 24-millimetre wingspan, while Aedes species are far smaller, with wingspans under 5 millimetres. Males beat their wings 450 to 600 times a second, powered by muscles that vibrate the whole thorax rather than attaching directly to the wings.

The aquatic years

A mosquito's life begins in water. Females lay eggs on the surface of stagnant pools, marshes, puddles, tree holes, or even the water trapped in a bromeliad's leaves. Some species are remarkably specific: Wyeomyia smithii breeds inside pitcher plants, its larvae dining on drowned insects, while Opifex fuscus tolerates salt marshes^[2]. Egg-laying style differs too. Anopheles mothers dot eggs singly onto the surface, Aedes drop them on damp mud to hatch only when flooded, and Culex females glue theirs into floating rafts.

Hatched larvae feed on algae, bacteria, and organic matter near the water's surface, breathing air through a siphon and diving when disturbed. After several molts they become pupae — active "tumblers" that flip their abdomens to swim but do not eat. The adult finally breaks free at the surface and flies off. In hot weather the whole journey from egg to adult takes as little as five days.

Why only females bite

Both sexes live largely on nectar, honeydew, and plant juices. Blood is strictly a female affair, and even then it is not about hunger. A blood meal supplies concentrated proteins needed to build eggs. Species like Anopheles and Aedes cannot reproduce without it, while some Culex manage a first clutch on sugar alone and need blood only later. A handful of genera, including Toxorhynchites, never bite at all^[3].

Finding a host is an elaborate sensory hunt. Mosquitoes track carbon dioxide and chemicals in breath from a distance, then close in using body odour. Of the 72 odour receptors on a mosquito's antennae, at least 27 are tuned to compounds found in sweat. Research shows people highly attractive to mosquitoes produce more carboxylic acids, and that malaria infections change a person's scent by raising aldehydes like nonanal, effectively making the sick smell more inviting — a clever trick that helps the parasite spread^[4]. Visual cues matter too: mosquitoes favour dark, high-contrast shapes and longer wavelengths associated with red and orange tones.

The bite itself is nearly painless because the mouthparts saw into skin with a thousandth of the force a needle would need. Saliva, injected to keep blood flowing, blocks clotting and dampens the local immune response — the same saliva that later triggers the itch and carries pathogens along.

Where they live

Mosquitoes occupy nearly every landmass on the planet. Only Antarctica and a scattering of islands remain free of them, because their freeze-then-thaw winters kill emerging adults before they finish a lifecycle. Temperate species endure cold better than tropical ones, some overwintering as diapausing eggs or sheltering as adults in buildings and hollow trees. In the Arctic, swarms emerge in staggering numbers during brief meltwater seasons, with a single swarm reportedly drawing up to 300 millilitres of blood per animal per day from a caribou herd.

Climate change is redrawing the map. Warmer, wetter conditions extend breeding seasons and open new territory. Models suggest southern Britain could support Plasmodium vivax transmission by 2030 and southern Scotland by 2080. The Asian tiger mosquito, Aedes albopictus, had by 2023 established itself across southern Europe and into northern France, Belgium, the Netherlands, and parts of England. Even Iceland recorded specimens in 2025 — a country previously without mosquitoes.

Ecology and deep history

For all their reputation, mosquitoes are woven into food webs. Larvae are among the most abundant creatures in ponds, eaten by dragonfly nymphs, fish, turtles, and ducks; adults fall prey to bats, swifts, spiders, and other dragonflies. Several flowers, including certain Platanthera orchids, depend on mosquitoes for pollination. Evolutionarily, mosquitoes arose no later than the Cretaceous, with fossils preserved in Lebanese and Burmese amber dating back roughly 99 to 125 million years. Molecular evidence hints at a Jurassic origin, though the group's great diversification came later.

Impact on humans

Nearly 700 million people contract a mosquito-borne illness each year, and more than a million die. Female Anopheles carry the Plasmodium parasites behind malaria; Aedes aegypti spreads yellow fever, dengue, and chikungunya; lymphatic filariasis travels in a wide range of species. Control efforts span drained breeding sites, window screens, bed nets, larvivorous fish, sterile-male releases, and experimental gene-drive strategies. Repellents such as DEET, picaridin, and plant-derived pyrethrum offer personal protection, though electronic ultrasonic devices have failed every credible test.

Mosquitoes have burrowed into culture as well. Siberian origin myths tell of the insect rising from the ashes of a slain giant; Japanese folklore casts them as blood-drinking spirits; Winsor McCay's 1912 cartoon How a Mosquito Operates ranks among the earliest animated films; and the de Havilland Mosquito aircraft of the 1940s borrowed the name for its speed. Engineers now study the proboscis itself, designing painless medical needles inspired by an organ evolved over 100 million years to pierce skin unnoticed.