Invertebrates
Mosquito
Anopheles gambiae · also called mosquito, malaria mosquito
The mosquito is, by a wide margin, the deadliest animal on the planet. It does not kill with venom or force but by carrying disease, and the diseases it moves between people — malaria above all, plus dengue, yellow fever, Zika, and others — kill hundreds of thousands of people every year and sicken hundreds of millions more.
Overview
Mosquitoes are found worldwide except Antarctica, wherever there is standing water for the larvae. Adults are slender flies 3–6 mm long, with two narrow wings, a long piercing proboscis, and feathery antennae. Both sexes drink nectar; females of most species also take a blood meal for the protein to make eggs.
The disease toll
Malaria, carried by Anopheles mosquitoes, kills most of the roughly half a million people who die of mosquito-borne disease each year — the majority young children in Africa. Other mosquitoes spread dengue, yellow fever, Zika, chikungunya, West Nile virus, and elephantiasis, each with its own species and geography.
How it finds you
A female tracks a host by exhaled carbon dioxide, then body heat, moisture, and skin chemicals such as lactic acid. Her saliva contains anticoagulants, and the immune reaction to it is the itchy welt.
Fighting it
Life starts in water, so removing small water bodies helps. Alongside bed nets and indoor spraying, there are now two malaria vaccines, mosquitoes carrying Wolbachia bacteria that block dengue, and genetically engineered mosquitoes designed to crash local populations.
Status
Mosquitoes are not assessed and not a conservation concern. Several disease-carrying species are expanding their ranges as the climate warms.
Mosquito: common questions
Why is the mosquito considered the deadliest animal in the world?
Because of the diseases it carries. Mosquitoes themselves are harmless as biting insects, but the pathogens they move between people cause an enormous toll. Malaria, spread by Anopheles mosquitoes, kills roughly half a million people a year on its own, most of them children under five in Africa, and mosquito-borne viruses such as dengue and yellow fever add hundreds of thousands more deaths and many millions of severe illnesses. No other animal, including snakes, dogs, or any large predator, comes close to that annual death toll, which is why the mosquito routinely tops lists of the animals most dangerous to humans.
Why do only female mosquitoes bite?
Because only the females need blood. Both male and female mosquitoes feed on nectar and other plant sugars for day-to-day energy. When a female is ready to produce eggs, however, she needs a large dose of protein and iron that plant food cannot supply, and a blood meal provides it. After feeding she rests while the eggs develop, then lays them in water and, in many species, seeks another blood meal for the next batch. Males lack the mouthparts to pierce skin at all and never bite.
How does a mosquito find me in the dark?
By following a trail of cues. The strongest is carbon dioxide, which you breathe out in a plume that a mosquito can detect and track from tens of metres away. As it gets closer it homes in on body heat, on the water vapour around your skin, and on specific chemicals in sweat and skin such as lactic acid, ammonia, and various fatty acids. Some people genuinely are bitten more than others because they produce more of these attractants or a more appealing blend, and mosquitoes also use vision to close the final distance.
Would eliminating mosquitoes be a good idea?
It is debated. There are about 3,500 mosquito species and only a few dozen are important disease vectors, so targeted suppression of those species, rather than wiping out all mosquitoes, is the realistic goal. Some ecologists argue that even the vector species fill roles as pollinators, as larval food for fish and dragonflies, and as adult food for birds and bats, and that removing them could have knock-on effects. Others point out that the specific disease-carrying species are often recent, human-associated, or invasive, and that their loss would be locally absorbed. New genetic tools have made the question practical rather than hypothetical.