The Top 9 Most Dangerous Bugs In The World

Wasps on a flower
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Not a lot of people like bugs or insects and there are many reasons why; they’re creepy, they’re crawly, and some look damn scary. While a lot of people think the most dangerous bugs come in large sizes that’s not necessarily the case. Some of the most dangerous bugs in the world are actually on the small side and while they don’t scary, they can pack a pretty nasty bite. One that could land you in hospital, or worse – dead!

There are plenty of bugs that deserved to be avoided if at all possible and it’s worth knowing what these bugs are, where they can be found, and what to do in the event that you come across one and happen to get bit or stung. 

We’ve put together a comprehensive guide of the nine most dangerous bugs in the world so you don’t have to go searching. 

Giant Japanese Hornets 

Hornet on a grid. Protection from insects - hornet, bee, wasp
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Native to South Asia, East Asia, and Mainland South East Asia, these hornets are the largest hornets in the world. They prefer to live in low mountains and forests and will almost completely avoid plains and high altitude climates. These species of hornet have recently been found in the Pacific Northwest of Northern America sparking concern that they could be an invasive species. While these hornets feast mainly on other insects, tree sap, and honey, they have been known to sting humans if they feel threatened. They have a body length of around 45mm, a wingspan of around 75mm, and their stinger is around 6mm long. 

Having such a long stinger allows them to inject more venom into their prey. For a human with an allergy, even just a small amount of venom from the Giant Japanese Hornet could kill you and a large amount of it could kill a human without an allergy. There are four different types of Giant Japanese Hornets; Queens, workers, and drones.

The queens tend to be a lot larger than the workers exceeding a body length of 50mm, while the workers tend to be between 35 and 40mm. The drones are male and although they are similar to the females they can reach a body length of 38mm but they lack a stinger. If you one flying around your head, remain calm and try not to antagonize them, they should move on and leave you alone. 

Mosquitoes

Close-up of mosquito sucking blood from human arm.
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Not a lot of people know this, but mosquitoes are the most dangerous bugs in the world. Killing around 1 million people every year by transmitting malaria. They have the ability to ruin any backyard BBQ or hike in the woods with their mere presence. A bite from a mosquito in most parts of the world causes nothing more than an itchy bite, in other parts of the world they can carry many deadly diseases. Although there are more than 3,000 species of mosquitoes, there are only three that bear primary responsibilities for the spread of human diseases.

Anopheles mosquitoes are the only known species to carry malaria. They also transmit filariasis (or elephantiasis) and encephalitis. Culex mosquitoes carry encephalitis, filariasis, and the West Nile Virus and the Ades mosquitoes carry yellow fever, dengue, and encephalitis. All these diseases have been known to affect humans and even kill them. While we have vaccines and medication that can help prevent us from getting seriously ill or dying, many in developing countries don’t have these luxuries. The World Health Organisation (WHO) estimates that every 30 seconds a child dies of malaria, and a staggering 500 million cases of malaria are reported every year. 

Kissing bugs

Shield Bug Or Stink Bug on plant. Extreme close up
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Kissing bugs might sound cute but their name is rather deceiving. These bugs get their name due to their habit of biting the lip of a human while they sleep. Now, this sounds pretty scary, and to be honest, it is. These blood-sucking parasites transmit Trypanosoma cruzi. Also known as the kissing bug disease or “Chagas”, which is known to kill approximately 12,000 every year. The kissing bug lives in cracks and holes of substandard houses in South and Central America. They normally become infected with Chagas after biting an animal or human who already has the disease. 

Chagas disease presents itself in two phases; the acute phase and the chronic phase. During the acute phase, symptoms are absent, mild, or unspecific. In less than 50% of people bitten the first visible signs can be a skin lesion or a purplish swelling of the lid of one eye. Additional symptoms can include fever, headache, enlarged lymph glands, pallor, muscle pain, breathing difficulties, swelling, and pain in the abdomen or chest.

During the chronic phase, the parasites are hidden mainly in the heart or digestive muscle. Around 30% of people bitten suffer from cardiac disorders and around 10% suffer from digestive (enlarged esophagus or colon), neurological, or mixed alterations. If you fear you’ve been bitten by a kissing bug, get yourself off to the hospital or speak to a doctor for treatment.

Fleas

Flea, Siphonaptera SEM
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Most of a flea’s life is spent searching for a place to call home. Somewhere they can enjoy a meal of sweet warm blood. These little parasites are normally found on reptiles, mammals, wild animals, domestic pets, and sometimes humans. They cause itchy, red spots on their host’s skin. Adult fleas grow to a size of about 3mm, which is often why they are so hard to spot. Their bodies are normally brown in color and ‘flattened’ sideways to enable them to move around easily on their host’s fur, skin, or feathers. 

They can leap a distance of up to 50 times their body length and are known to reproduce very quickly, with a female laying around 2000 eggs in its lifetime. While these pests aren’t likely to kill you they can carry deadly diseases such as the plague. It’s important that you get seen by a doctor if you think you may have been bitten by a flea so they can provide treatment. If you have any animals it’s also worth talking to your vet so they can advise what the correct cause of treatment and preventative would be best for your pet.

Tick

Tick - parasitic arachnid blood-sucking carrier of various diseases
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Ticks might not sound that scary but these small bugs can carry Lyme Disease. These spider-like parasites are approximately 3 to 5mm in length and are widely distributed around the world. They tend to be quite prevalent in the summer months and like hiding in long grass, woodlands, and open areas of unmaintained grassland. Once they have found a suitable spot on their host they can feed for around 8 to 10 days without being perceived by their host.

Lyme Disease is common with ticks and although it’s not necessarily deadly it can have long-lasting effects for the person who contracted it. Often times Lyme Disease goes undiagnosed, however, it can cause headaches, fever, joint stiffness, and even heart problems. If you find a tick on yourself it’s best to remove it as soon as possible using a tick puller and consult with your doctor just to be on the safe side. 

Puss Caterpillar

group os hairy caterpillars
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Also known as a pussy moth or southern flannel moth, these bugs are considered one of the most dangerous bugs in the world due to their venom. Exposure to the fur-like spins on this caterpillar can cause severe skin irritation and severe radiating pain which has been described by many as similar to that of a broken bone or blunt force trauma.

Sometimes the reaction is localized to the affected area, however, it can cause additional symptoms such as a burning sensation traveling up the limbs, swelling, nausea, headaches, abdominal distress, rashes, blisters, and sometimes chest pain, numbness, and breathing difficulties. If you come into contact with one of these it’s advised that you seek immediate medical attention and with all those symptoms is not hard to see why.

Assassin Caterpillar

Fuzzy Caterpillar
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Similar to that of the Puss Caterpillar the Assassin Caterpillar gets its name from its potentially deadly venom. It has already been the cause of several deaths in Brazil and was classified as the most venomous caterpillar in the world by the Guinness world records. These caterpillars are around 4.5 to 5.5 cm long with colors ranging from green to brown making them very well camouflage to predators.

They have rows of tubercles along their body which hold easily detachable spines of varying sizes. These spines are what the caterpillars use to inject their venom and symptoms include inflammation, headaches, fever, vomiting, and a severe bleeding disorder within 24 hours after injection. Getting yourself to the emergency department as soon as possible can save your life.

Brazillian Wandering Spider

A brazilian wandering spider (Phoneutria sp.) waits in ambush on a leaf at night in Costa Rica.
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There are many among us with arachnophobia and they have a good reason for it. These eight-legged, creepy crawlies are known to be some of the most deadly bugs in the world and the Brazilian wandering spider is definitely one for this list. The Brazilian Wandering Spider is a highly aggressive spider native to Brazil, Central, and South America. Its bite delivers a neurotoxic venom that could kill a human, child, or animal in a matter of hours, but with the availability of antivenom, the risk of death is relatively low. 

These spiders are large with bodies of up to two inches and a leg span of a whopping 7 inches, so they aren’t exactly hard to miss. The colors of this species vary, the majority are hairy and mostly brown or grey in color with light-colored spots on their abdomen. Once bitten by one of these spiders the initial symptoms include severe burning pain at the site of the bite, sweating, and goosebumps. Within 30 minutes symptoms become systemic and include fast or slow heart rate, high/low blood pressure, nausea, hypothermia, vertigo, blurred vision, convulsions, and abdominal cramping. 

Brown Recluse Spider

Brown Recluse spider
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The Brown Recluse Spider has a necrotic venom that requires immediate medical attention. These spiders are native to Midwestern and Southern America and usually between 6 and 20mm in size, although they can be larger. As their name suggests they are typically light to medium brown in color, however, they also range from whitish to dark brown or even blackish gray. They tend to a violin-like pattern on their backs however, this is not a definitive identifier. Another interesting fact about these spiders is that they only have six eyes as opposed to eight like other spiders have.

The venom from a Brown Recluse Spider can destroy blood vessels, tissues, and nerves. The initial symptoms from a bite include red, tender, or inflammation around the area of the bite which can then lead to a severe burning sensation with 3 to 8 hours after the initial bite. For those that are healthy and don’t react to the bite it can be left and will heal within 3 to 5 days, however, it’s advised that you do receive treatment. Severe symptoms include chills, vertigo, fever, rash, and vomiting.

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Justine King is from the UK and has been a full-time traveller and freelance writer since 2020 after a 6-year career in Hospitality. Clients benefit from her love and knowledge of the sector as she creates informative and inspiring articles to help guide readers totheir next travel destination.