10 Bugs That Will Make You Squirm

A yellow banana slug crawling over wet moss

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Whether they are insects, worms, or arachnids, there are creatures both harmless and harmful that elicit fright and disdain. Some are insects that can thrive indoors, and humans encounter them as unwanted house guests. Others, like scorpions, are highly venomous and can be dangerous to people if they are disturbed. Some are parasites that rely on human blood to survive. 

From slimy slugs to swarming ants, here are 10 creatures that make people squirm. 

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A red and black tick walking on a green leaf

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Ticks are arachnids that feed on the blood of large mammals, including humans. They find their hosts by perching on tall grasses and bushes, and transfer onto animals that pass by and brush the vegetation. Once situated, ticks bite their hosts, insert a barbed feeding tube, and become difficult to remove as they anchor in place and engorge with blood.

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A dark brown scorpion with a curled tail on a log

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Scorpions are large, predatory arachnids with fearsome-looking pincers and a curved tail with a stinger. They look dangerous for a good reason—their sting is highly venomous. All scorpions possess venom that can paralyze or kill their prey, which includes crickets, lizards, and small mammals. Of the 1,500 species of scorpions, about 30 are venomous enough to be a danger to humans.

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A red leech on a forest floor

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Leeches are parasitic, blood-feeding worms that feed on larger host animals. They are famous for their role in medicine and were commonly used to extract blood from patients with a variety of ailments until the 1800s. Today, using leeches is still considered a valid medical practice in some rare cases like reconstructive surgery. 

The majority of leech species are found in freshwater, though there are leeches found in marine and terrestrial environments as well. The giant Amazon leech is one of the largest in the world. It can grow up to 18 inches in length, with a four-inch-long, bloodsucking proboscis. 

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A brown cockroach with spiky legs on a tree branch

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There are about 4,600 species of cockroaches—30 of which are associated with human habitats. They are hardy creatures that can survive in many conditions, and some cockroaches can go without food for two to three months. The American cockroach, one of the most common species spotted in houses, can eat paper, dead skin cells, leather, and many other things that humans would consider trash. Due to their remarkable endurance, it is commonly said that they would inherit the Earth if human civilization were to disappear.

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House Centipede

A centipede with long legs on a green leaf

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House centipedes are a common sight in dark, damp indoor spaces like basements, bathrooms, and cellars. With up to fifteen pairs of long legs, they are agile creatures that can be hard to capture as they scurry across the floor. In the outdoors, they are often found burrowing under rocks or logs. Though house centipedes are venomous, their sting is not considered dangerous to humans. Plus, since they are capable predators of termites, spiders, cockroaches, and other insects, having one in the house could be considered a net benefit. 

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Fire Ant

An ant with a red head and black abdomen sitting on a green leaf

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Fire ants are several species of ants with red or light brown bodies that will swarm and sting when disturbed. They live in colonies that usually appear as large mounds, but can also be hidden under rocks, logs, or sidewalks. Their sting is painful and potentially dangerous, especially to those who form an allergic reaction to the toxin. The fire ant that is found in the United States, Solenopsis invictais an invasive species imported from South America. 

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Bed Bug

A single bed bug on a piece of pink knit fabric

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Bed bugs are small insects that feed on human blood during the night. The bites, which appear as inflamed red bumps or flat welts, are usually accompanied by incessant itchiness. Bed bugs are found in regions all across the world and are hard to eradicate. 

Bed bugs have had a worldwide resurgence since the late 1990s, with many more infestations being reported, especially in developed countries. Researchers believe the increase may be due to the insect's newfound resistance to insecticides.

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Brown Recluse

A brown spider with long legs climbing a wall

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The brown recluse is a venomous spider native to the midwestern United States. A mature brown recluse is about the size of a quarter and uniformly brown, except for a "fiddleback" marking on its dorsum that looks like a violin. The spider is not aggressive, and if it does bite a human, it usually only results in localized swelling. In some cases, however, the wound can develop into a necrotic lesion that eats away at skin and muscle tissue. These bites can be long-lasting and leave permanent scars. In extreme cases, they can turn life-threatening.

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A slug peering over the edge of a leaf

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Slugs are a type of mollusk that spend their lives covered in mucus. The mucus helps to keep their vulnerable bodies, which are mostly water, from drying out. The mucus produced by banana slugs can help defend against predators—researchers have found snakes with their jaws glued shut by the mucus. Slugs prefer to hide under rocks and logs to retain their body moisture, and are often only seen in the open after rain. Though they are harmless to humans, slugs can be voracious eaters of plant matter and are sometimes considered agricultural pests. 

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Head Louse

A close-up photo of a louse on hair

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Head lice are tiny, wingless insects with a parasitic relationship to humans. They live their entire lives in human scalps, feeding on blood. They reproduce by laying eggs, known as "nits," that attach directly to hair follicles near the scalp. Lice are especially common among children, and lice infestations are often reported in schools and day cares.