When we think of deadly animals, we often picture fearsome predators with claws, fangs or venom. But some of the most lethal creatures on the planet are no bigger than a fingernail – and they can be found buzzing in your own back garden.
Flies, particularly biting species like mosquitoes and tsetse flies, are responsible for millions of deaths every year, spreading diseases that can disfigure, debilitate or kill.
We reveal the tiny terrors whose bite is far worse than their buzz – and how these deceptively small insects earned their place among the deadliest animals on Earth.
Deadliest flies
Tsetse fly
The tsetse fly carries a deadly disease called sleeping sickness. Like malaria, sleeping sickness is caused by a parasite and transmitted to victims via a bite. It takes its name from the confusion, numbness and difficulty sleeping experienced by sufferers. The disease can be fatal, but even the symptoms can be unbearable – fever, severe headaches and seizures.
Mosquito
Not just one of the deadliest insects, the mosquito is the deadliest animal in the world, responsible for up to a million human deaths a year. While they don’t kill directly, mosquitoes carry diseases and viruses such as malaria and dengue, which they transmit to humans and animals while they are feeding. The deadliest mosquito-borne disease is malaria.
Sand flies
Sand flies spread Leishmania parasites, which can cause visceral leishmaniasis, a disfiguring and sometimes fatal disease. If not treated, severe cases can be deadly, since it affects the internal organs.
Botflies
While botflies don’t carry deadly diseases, their larvae burrow into human or animal flesh, causing myiasis, a painful and sometimes dangerous infection. In rare cases, the larvae can migrate to other body parts, such as the eyes or brain, causing serious damage. Botflies particularly affect rabbits, rodents, horses and cattle.
Black flies
Although black flies don’t tend to be deadly to humans, their outbreaks have been responsible for the deaths of many domestic and wild animals. Infected black flies carry Onchocerca volvulus, the parasite that causes river blindness, which can result in permanent vision loss and skin disease. The name “river blindness” comes from the fact that the black fly breeds in fast-flowing rivers, and the disease can cause severe itching, skin rashes, and, if the larvae reach the eyes, blindness.
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Deer flies
While it’s not common, deer flies can sometimes transmit diseases such as tularemia in some regions. This bacterial disease – known as “rabbit fever” or “deer fly fever” can be fatal without antibiotic treatment.
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