Blister Beetle

Last updated: October 7, 2022
Verified by: AZ Animals Staff
© Suede Chen/

Blister beetles release a toxic fluid that causes blistering when they're threatened.


Blister Beetle Scientific Classification


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Blister Beetle Conservation Status

Blister Beetle Facts

Group Behavior
  • Infestation
Fun Fact
Blister beetles release a toxic fluid that causes blistering when they're threatened.
Most Distinctive Feature
They secrete cantharidin, a poisonous chemical that causes blistering of the skin,
Distinctive Feature
Narrow thorax and wider head
Arid regions
  • Diurnal/Nocturnal
Favorite Food
plants in the family Solanaceae, Asteraceae, Fabaceae, and Amaranthaceae. Larvae are insectivorous, feeding on grasshoppers and bee larvae
Beetle (Insect)
Common Name
Blister beetle
Special Features
Blister beetles release a toxic fluid that causes blistering when they're threatened.
Number Of Species
North America

Blister Beetle Physical Characteristics

  • Multi-colored
Skin Type
3 months
1cm to 2.5cm (0.4inch - 1inch)

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Blister beetles release a toxic fluid that causes blistering when they’re threatened. 


Insects in the family Meloidae are called Blister Beetles. They are found in different colors, body shapes, and sizes. Unlike other beetles that typically have robust and rounded bodies, blister beetles have a narrow thorax, a distinctive narrow “neck,” and a wider head. Their name refers to their ability to produce a blistering chemical when a predator attacks. Their conspicuous color warns potential predators that the insect is toxic. Adults feed on plants, but their larva form is insectivorous. 

Blister Beetles Species, Types, and Scientific Name

Blister beetles are insects in the family Meloidae. Their name refers to their ability to release a toxic chemical called cantharidin, which can cause blistering if it comes in contact with skin. This defensive secretion protects the beetle from predators. 

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There are about 7500 species of beetles in this family, and they all have different appearances. They’re divided into 120 genera and four subfamilies. Blister beetles belong to the beetle order Coleoptera along with over 400,000 other species of beetles. However, their appearance is significantly different from the characteristic appearance of insects in this order. 

Appearance: How to Identify Blister Beetles

Blister beetles are long soft-bodied insects. Their head is deflexed, fully exposed, and abruptly constricted to form a narrow neck (the thorax). Most species of blister beetles have elongated abdomen covered fully by their wings. However, in a few species, the abdomen is rounded, and their wings are shorter. Their body length varies between 3/4cm to 2cm in most species. 

In blister beetles, size and coloring vary from one species to the other. These beetles vary in color from yellow to gray. Their coloring is typically bright and conspicuous. Their conspicuous coloring is meant to warn predators of their toxicity. They are typically striped, variegated, or flat. The varieties with stripes usually come in shades of gray or brown with yellow stripes that run lengthwise. The ash-gray variety is completely gray, while the black blister beetle is completely black. Margined varieties of this bug are typically black but have a gray or cream band on the edges of their wing cover. In all varieties, their wing cover is soft and flexible, and they have relatively long legs. 

Blister beetles are gregarious. They’re usually found in large numbers congregated in specific areas of a field or garden. While they’re not serious pests, they may cause damage to certain crops under specific conditions. When threatened, the blistering chemical they produce is toxic to livestock such as horses and other grazing animals. This is a problem for farmers since the insect often appears in alfalfa and other forage crops on which these livestock animals feed. 

Habitat: Where to Find Blister Beetles

Blister beetles are found worldwide. More than 250 species are present in the United States. They’re swarming pests of fields and gardens, usually found in association with various leaf crops, landscape flowers, plant blossoms, and hay crops. However, they may also be found in locations where their typical host plants are absent. Blister beetles spend their winter in the larval stage. They pupate in spring and emerge as adult beetles in the early summer months. 

Diet: What Do Blister Beetles Eat?

Adults are herbivores. Although they’re not prolific pests, they’re sometimes problematic in gardens and fields because they feed on various plants. Their common host include plants in the family Solanaceae, Asteraceae, Fabaceae, and Amaranthaceae. They feed on the leaves and flowers of these plants and can cause serious defoliation of these plants, especially when they congregate in large numbers. Some field crops they typically feed on include alfalfa, canola, soybeans, dry beans, sweet clover, sugar beets, and potatoes. 

In the larval stage, this beetle is insectivorous. They feed on the egg pods of grasshoppers. They can also attach to bees. As bee lice, they’re carried to the nest of bees, where they feed on eggs and bee larvae until they develop into the pupal stage. 

What Eats Blister Beetles?

Blister beetles have a formidable defense against predators. When threatened or crushed, they release a substance known as cantharidin. This chemical can cause tissue damage and blistering. They’re also toxic if swallowed. The chemical is quite stable and persists even in dead and dried-up beetles. 

Prevention: How to Get Rid of Blister Beetles

Blister beetles are not always problematic. In fact, they may even be beneficial in some respect since their larval form helps to keep grasshopper populations under control. However, adult blister beetles feed on the leaves and flowers of plants. They form swarms that can cause considerable damage to plants. The toxic chemical they produce also makes them a threat to grazing livestock.

You should inspect your garden frequently to identify the beetle and take steps to mitigate its spread early enough. Adults usually emerge in the early summer months. You can pick them off and remove them as soon as you spot them. This should be done as quickly as possible before they become established. It would be best if you hand-picked them with gloves to protect yourself from the blistering chemicals they produce. 

Diatomaceous earth is effective in keeping the beetles under control. You can spread this around threatened plants to form a barrier. Oyster shell lime is also an effective barrier, but this doesn’t kill the insects. Additional tips to follow include: 

  • Trim grass and weeds around the margins of your garden 
  • Use row covers in the early summer months 
  • Avoid growing certain plants 
  • Encourage birds to visit your garden 
  • Apply a biopesticide 

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About the Author

Abdulmumin is a pharmacist and a top-rated content writer who can pretty much write on anything that can be researched on the internet. However, he particularly enjoys writing about animals, nature, and health. He loves animals, especially horses, and would love to have one someday.

Blister Beetle FAQs (Frequently Asked Questions) 

Can blister beetles harm humans?

Yes, the blister beetle produces a toxic blistering agent known as cantharidin. This can cause serious irritation and blistering when it gets on the skin, throat, mouth, or eyes of a person. Although non-threatening, the blistering can be painful.


Why are they called blister beetles?

The common name of blister beetles is a reference to their ability to produce a toxic chemical that causes blistering if it comes in contact with human skin.

How do you treat blister beetles?

Blisters caused by blister beetles typically disappear on their own in about a week. To treat a local reaction, you can wash the site with warm soapy water daily and apply an antibiotic or a topical steroid to the wound to prevent secondary infection.

How are blister beetles threats to livestock?

The blistering chemical produced by blister beetles causes a toxic effect in livestock known as cantharidin toxicosis. Since these insects infest plants like alfalfa which is used for making hay, it poses a health hazard to animals like horses, sheep, and cattle, especially when they’re ingested in large quantities. The chemical cantharidin is quite stable and is still toxic even when the insect is dead.

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  1. Wikipedia, Available here:
  2. Texas A&M Extension / Charles Allen, Available here:
  3. Planet Natural Research Center, Available here:

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