There are many contenders for the top 10 deadliest animals in the world—forget the black-footed cat and the desert taipan, widely considered the world’s most venomous snake. Its venom has the highest toxicity of any snake venom and is estimated to kill around 100 humans. But insects are actually the most dangerous group of animals in the world to humans. This is largely due to their ability to carry and spread deadly diseases, from malaria to the Black Death.

Many species of insect feed on vertebrate blood, putting them in a prime position to carry nasty bacteria, viruses, and parasites from victim to victim, and often from animal to human. 

This list of deadly insects will cover such disease carriers, as well as those that can kill through toxic stings and bites, and even by destroying our crops.

Insects have been implicated in major history-defining events, from devastating plagues to colonial expansions, and their effects have shaped our own human evolution. Size really can be deceptive.

Read on to find out more about the world’s deadliest insects.

10. Blister Beetles

Kicking off our list of deadliest insects, in 10th place, is the blister beetle. This has the potential to be deadly to humans, but in reality, is not, as you would have to eat quite a few of them.

What they are more likely to kill are horses, as they can get mixed up into the hay or alfalfa they eat.

Blister beetles secrete a toxin (and defensive agent) called cantharidin, which causes skin blistering in humans. It has however been used in the past as a folk medicine, thought to be effective against warts and even rabies, but most commonly as an aphrodisiac.

In the past, it has been a major ingredient in “love potions”. This was a risky business, however, as the toxin can still kill in high enough quantities. In the 1950s a man was imprisoned for the deaths of two women whom he had given cantharidin-laced candies to in order to seduce them.

9. Locust (Locusta migratoria)

Locusts are not typically considered “deadly” in the sense of directly killing humans through venom or disease transmission, but their effects certainly can be.  These swarming phases, which turn the normally solitary insect into a mass of millions, are triggered by a dry spell followed by rapid rainfall and vegetation growth.

The drought forces them together onto the remaining areas of vegetation and the rainfall and subsequent abundance of food allows them to breed rapidly – creating a perfect storm. The major agricultural damage such swarms can cause can lead to famine and consequently many human fatalities.

8. Assassin caterpillar (Lonomia obliqua)

Spiny Venemous Caterpillar, Machalilla, Manabi, Ecuador

In eighth place is the fabulously named Assassin caterpillar. Although its name perhaps overstates the kill count of this caterpillar, it is responsible for a number of fatalities. The larva stage of the giant silkworm moth, this caterpillar is known as the world’s deadliest.

Its toxicity comes from its venom-injecting bristles that function as a defence mechanism against predators. The venom is stored in a sac at the base of each hollow bristle and when a bristle punctures the skin of a victim the venom flows through. The toxins have anti-coagulant properties, disrupting blood’s ability to clot properly. Symptoms include a burning sensation, vomiting, kidney failure, internal bleeding, and in rare cases, death. 

7. Fire ants (Solenopsis genus)

Although generally not fatal, Fire ants (genus Solenopsis) are considered one of the most dangerous insects in the world due to their aggressive behavior and painful venomous stings. Their venom, in particular, identifies a small number of proteins that can cause allergic reactions (anaphylaxis) in some individuals that can affects their nervous systems. This may explain why some fire ant sting victims report hallucinations and similar symptoms, particularly after multiple stings.

6. Bees and wasps

Outside of disease carriers, there are actually very few insects that are dangerous, venomous or poisonous enough to be fatal to humans. One group of deadly insects that are responsible for numerous fatalities however is Hymenoptera – the order that includes bees, wasps, and ants. If you are unlucky enough to be one of the small percentage of people that have have an anaphylactic allergic reaction, bee stings can in rare cases be fatal.

• Honeybees typically die after stinging because their stinger is barbed, causing it to become lodged in the skin of the victim, usually a mammal. When the bee tries to pull away, the stinger and parts of its abdomen, including digestive and reproductive organs, are ripped out, leading to death. This is a consequence of the bee’s anatomy and is not a deliberate act of self-sacrifice. 
• Bees always have at least a few branched, called plumose, hairs somewhere on their bodies. These trap pollen grains and aid the females in carrying their pollen loads back to the nest. Wasps don’t have branched hairs. Here below a Wasp:

Every year in the UK there around ten reported deaths from wasp or bee sting reactions.

5. Asian giant hornet (Vespa mandarinia)

The Asian giant hornet is the world’s largest hornet and is known for its powerful sting and venom, which can cause severe pain, swelling and allergic reactions leading to death.  While not actively hunting humans, they can be aggressive and attack when disturbed, especially near their nests. 

The Asian giant hornet is native to East Asia and Japan, where they cause an average of 30-50 deaths per year. In China, they were responsible for 42 deaths in a single province during a population surge in 2013. 

4. Kissing bugs (Triatominae subfamily)

In fourth place is the kissing bugs members of the Triatominae subfamily of insects. This Kissing bugs can transmit the parasite that causes Chagas disease, a potentially fatal illness. 

While the bite itself is not usually dangerous, kissing bugs defecate after feeding, and the parasite can enter the body through the bite wound, eyes, or other mucous membranes if the feces are rubbed in. Chagas disease can lead to serious heart and digestive issues, and in some cases, it can be fatal. 

3. Fleas (Siphonaptera genus)

Fleas are small, wingless insects known for their ability to jump long distances relative to their size. While they are primarily known as pests that cause itchy bites on humans and animals, some flea species can transmit deadly diseases. The most infamous example is the bubonic plague, which decimated populations in the past. 

Caused by the bacterium Yersinia pestis, the bubonic plague is the most well-known disease spread by fleas. Historically, it was responsible for the Black Death, which wiped out a significant portion of Europe’s population. While treatable with antibiotics today, it remains a public health concern. 

Allergic Reactions:

• Some individuals are allergic to flea saliva, which can lead to more severe skin reactions, including intense itching, inflammation, and secondary infections from scratching. 

Flea Allergy Dermatitis:

• Pets can also develop severe allergic reactions to flea bites, leading to excessive scratching, hair loss, and skin damage. 

Flea Biology and Infestations:

• Fleas have a four-stage life cycle: egg, larva, pupa, and adult. 
• Adult fleas live on their hosts (animals or humans), while the immature stages (eggs, larvae, and pupae) develop in the environment. 
• Fleas reproduce rapidly, and infestations can quickly get out of control if not addressed promptly. 
• Flea infestations are more common in warm, humid environments. 

Fleas jump using a combination of stored energy in a rubbery protein called resilin and a lever-like mechanism in their legs, enabling them to launch themselves up to 200 times their body length. The process involves compressing resilin to store energy, then releasing it to extend the legs and propel the flea forward and upward. 

2. Tsetse fly (Glossina genus)

In second place is the tsetse fly, its main killer is its ability to transmit African trypanosomiasis, also known as sleeping sickness, a parasitic disease that can be fatal if left untreated. Although not all tsetse flies carry the disease, and only a small percentage are usually infected, the bites of those that do can be very dangerous.

Tsetse flies transmit the disease through their bites, as they feed on blood. The parasite, Trypanosoma brucei, enters the bloodstream of the host (human or animal). In humans, the disease progresses in stages, beginning with fever, headache and fatigue, and can lead to neurological symptoms such as confusion and sleep disturbances if left untreated. Eventually, it can lead to death.

Efforts to control the tsetse fly and reduce the spread of sleeping sickness involve various strategies, including trapping, insecticide application, and genetic research.