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What Is a Blister Bug?

By Jillian O Keeffe
Updated Mar 05, 2024
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Technically known as a blister beetle, a blister bug is an insect that produces chemicals that can burn skin and produce blisters. Many different species of the bug exist all over the world. Typically, they feed on vegetative crops and can occur in large groups. The burning chemical, cantharidin, is poisonous to animals, and acts as a deterrent to animals who might otherwise eat them.

Scientists classify animals and insects into groups depending on how related they are to each other. Each blister bug is of a particular species; for example, Epicuata vittata. Groups of species then fall into genus groups, such as Epicuata or Lytta. Collections of all the genera, which is the plural of genus, fall into the family Meloidae.

Over 2,500 species of blister bug are included in the Meloidae family. Even though the beetles live all over the world, they all contain a chemical called cantharidin. Some insects only produce a stinging or poisonous chemical from specialized glands, and release them only in certain situations, such as directly at a potential attacker.

A blister bug does not release cantharidin deliberately. Instead, it has the chemical inside its body, running through the tissues and blood of the insect. The presence of this blistering substance is not useful for an individual beetle, faced with a predator that wants to eat it, or a situation where the beetle is going to be squashed. Throughout the species' evolution, however, the unpleasant and dangerous burn from the chemical teaches animals and humans to avoid it. The species then have less risk of being eaten.

Sometimes, however, the beetles suffer predation or accidental crushing or touching. When the adult is squashed, or a human, for example, touches them in a manner which scares the beetle, then the cantharidin comes out of the body and burns the skin. Typically, the adult beetles feed on plants, and animals may accidentally eat them during grazing. Just one beetle is capable of killing an animal, and as the cantharidin persists in the bug even after death, the beetle need not be alive to kill an animal.

Visually, a blister bug has a cylinder-shaped body, and an obvious neck between the body and the head. They come in a variety of colors, from dull brown to stripy yellow. Often, the bugs group together in swarms where food is present. The adults are agricultural pests, but the immature forms may be useful as pest controllers, because they eat the eggs of grasshoppers and crickets.

Frequently Asked Questions

What exactly is a blister bug?

A blister bug, more commonly known as a blister beetle, is an insect belonging to the Meloidae family. These beetles are known for their defensive secretion of a blistering agent called cantharidin, which can cause skin irritation and blistering upon contact. They are found in various environments and are often recognized by their elongated bodies and soft elytra (wing covers).

How does cantharidin affect humans and animals?

Cantharidin, the compound produced by blister beetles, is a potent vesicant that causes blistering of the skin. In humans, contact with cantharidin can lead to painful blisters and skin irritation. For animals, ingestion of these beetles, often accidentally through contaminated hay, can be fatal. Symptoms in animals include gastrointestinal upset, renal failure, and in severe cases, death.

Where are blister beetles commonly found?

Blister beetles are widely distributed across the world, with a high concentration in temperate regions. They are commonly found in fields, gardens, and meadows, especially during the warmer months when they are most active. These beetles are attracted to flowering plants, where they feed and mate, and can sometimes be found in swarms.

What do blister beetles eat?

Blister beetles have a varied diet depending on their life stage. The larvae are typically insectivorous, feeding on grasshopper eggs and other insects, which helps control pest populations. Adult blister beetles primarily consume plant materials, including leaves, flowers, and pollen, which can lead to damage in agricultural settings if present in large numbers.

How can I identify a blister beetle?

Blister beetles can be identified by their distinctive physical characteristics: an elongated body, a broad head connected to the body by a narrow neck, and soft elytra. They range in size from about 0.5 to 2.5 centimeters and can vary in color from black to bright metallic hues. Caution is advised when handling them due to their ability to secrete cantharidin.

Are blister beetles beneficial or harmful to the environment?

Blister beetles play a complex role in the environment. As larvae, they can be beneficial by controlling grasshopper populations, which are often agricultural pests. However, adult blister beetles can damage crops and pose risks to livestock when ingested. Their impact is thus a balance between their beneficial predatory larval stage and the potential harm adults can cause in agricultural settings.

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Discussion Comments

By literally45 — On Oct 05, 2013

@donasmrs-- Some blister bugs can fly, but I think they're more commonly found in hotter climates like Africa and South Asia.

My brother returned from his trip to Africa with huge blisters on his body because of an African blister bug. He said that the flying bug flew into his hotel room at night. He chased it for a while and finally killed it getting some of the chemical on his body. He had to use antibiotic creams for weeks to treat the blisters and the poor thing was in so much pain.

By donasmrs — On Oct 04, 2013

@burcidi-- People have different ways of getting rid of blister bugs. Some people use pesticides. Others, like me, who don't like chemicals use other ways. My method is putting containers under them and using a hose to water down the plants they're holding on to. Blister bugs love to hang out in large groups. They can't fly, they only crawl and they can't swim either. So if you get them in water, they won't live for long. And since they hang out in bunches, you can get rid of them fairly quickly.

Regardless of what method you use, make sure to wear gloves and long clothing. Don't let kids or pets get near them at any point.

By burcidi — On Oct 04, 2013

What is the best way to get rid of blister bugs?

My garden has recently been infested with them. They seem to be attracted to my flowers.

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