Blister Beetle Life Cycle: How Many Life Stages Does A Blister Beetle Go Through?

In this article, I will describe the blister beetle life cycle in detail.

Blister beetles live a very unique and complex life cycle that is different from other insects.

Their larvae are predaceous from the get-go, hunting for grasshopper eggs in the soil. As they forage for food, they grow bigger and, after about four stages, turn into pseudo pupae.

The pupae then overwinter, lying in wait for the temperatures to rise so that they can finally come out as adults, feed, and mate.

These beetles can live a lifecycle that lasts just three months – but they are also capable of living beyond three years if the need arises!

If you would like to know more about their life cycle, I will share all the necessary details in this article.

Blister Beetle Life Cycle
Blister Beetle: Tricrania sanguinipennis

What Are Blister Beetles?

Let us first give a brief background about these much-feared and reviled beetles.

Blister beetles consist of several species of the family Meloidae that feed on crops, flowers, and grasses.

They have grey or black hard-shell bodies with either orange or yellow stripes running down their backs.

They range from about 10-20 mm in length and contain an oil called cantharidin – a powerful chemical that is used as a defense mechanism against predators.

When ingested or touched by humans, this oil can cause serious skin blistering and inflammation.

Additionally, the larvae of these insects affect forage crops such as clovers and alfalfa. This makes them dangerous to livestock if not properly managed.

Life Cycle of Blister Beetles

Blister beetles have a strange and unique lifecycle. In fact, they can complete a whole lifecycle in just 30 days – but sometimes their life stages can keep running for beyond three years!

Adults Emerge To Mate

These bugs overwinter in the soil as pseudo pupae.

In June and July, adults emerge from these pupae once the temperature and moisture improve during spring.

As adults, the insect congregates on plant leaves and flowers and feeds on pollen.

Nuttail’s Blister Beetle

After their feeding frenzy, the adults turn to mate and produce the next generation.

Blister Beetles most commonly have only one generation a year, especially in the Northern Plains.

However, in the south, they have been known to produce two generations.

Eggs Are Laid

Once they start mating, the activity happens quite often. Every now and then, the females start laying eggs.

It takes between two to three weeks after mating to lay eggs. They lay about six clutches each time, and every one of these may have upto hundred eggs.

Typically, the eggs are laid in small orifices in the soil (about 1 to 2 inches deep), somewhere where the young larvae will have enough food for their survival.

Sometimes, they might also be laid under stones or even on the plants which the adults were feeding on.

But plant food is not the only thing the females are looking for.

The abundance of blister beetles is influenced by grasshopper abundance since grasshopper eggs are one of the most important food sources for larvae.

The dependence is so high that in years with high grasshopper populations and the ones that follow, you can see an increase in blister beetle populations.

Iron Cross Blister Beetle

The Larvae Come Out

After about 10 to 16 days, the eggs start to hatch, and the little larvae come into the world.

They would spend four distinct stages gathering strength and becoming ready to emerge as beetles.

The first stage is perhaps the most energetic one.

The beetle larvae are called triangulin in this phase. Despite being new to the world and their surrounding, they are able to reach their food.

That’s because these larvae are blessed with tiny legs designed so that they can walk around in the soil.

The larvae immediately find and start eating grasshopper eggs to their heart’s content. This goes on for some time until they are full to the brim.


Once they are done, these larvae transform into grub-like creatures, which is what they continue to look like till their fifth or sixth instar.

After the fifth or sixth stage, they start becoming lazier and lazier and stop moving about completely. Their outer shell also becomes very hard.

Once this happens, their muscles start to degenerate, and breathing falls to a very low level.

All of this is meant to make them capable of surviving for more than a year in this form. This is the pseud pupa stage that we started our story with.

Blister Beetle


Before becoming a pupa, the larvae molt several times. Toward the end, they go back to the soil from which they emerged.

Their pupae stage looks very nearly like the adult beetle, except for the wings and legs, which are held very tightly to the body.

When they start out, the pupae are white, but with time the color darkens as they get ready.

The pupae are initially whitish in color and grow darker as they mature and lie in wait for the spring season to come.

And thus restarts the cycle of life once again in spring and fall.

What Do Blister Beetles Eat?

Blister beetles are a bit of a plant pest. The adults, as I mentioned earlier, feed on plants.

This could include anything from tomatoes to peppers, eggplants, beans, potatoes, and more. Basically, anything you might be growing in your garden.

They have a particular love of legumes, by the way.

If you think your flowering plants are safe from them – think again. These beetles can swarm your home garden and start sucking down your beautiful flowers.

Spotted Blister Beetle

But the most important thing they feed on is alfalfa.

Why is this important? Well, alfalfa hay is fed to horses, and the chemical that these beetles produce is toxic to horses.

Lastly, the larvae are big on grasshopper eggs, so they can be very helpful in a garden full of these pests.

But you wouldn’t want to bring blister beetles into your garden just to get rid of grasshoppers, now would you?

Do Blister Beetles Fly?

Yes, as I said earlier – these beetles can fly short distances.

They tend to travel in swarms when they are doing this, so it is important to watch out for them when they are flying.

However, their normal course of movement is just walking; they don’t fly a lot.

Neither do they need to – after all, their reflex bleeding is a protective method that keeps them safe from most predators.

Frequently Asked Questions

What metamorphosis are blister beetles?

Blister beetles are insects that undergo complete metamorphosis. This process involves four distinct stages: egg, larva, pupa, and adult.
Blister beetle larvae feed on other insects, such as grasshopper eggs or caterpillars; however, as adults, they feed on plants.
The adult stage of the blister beetle is the most recognizable: it has a yellowish or brownish body with a black head and thorax.
Their bodies have grooves along the abdomen which make them stand out from other species of beetles.

What stage do blister beetles cause damage?

Blister beetles cause damage at the adult stage when they feed on economic crops.
Generally, they feed on young pollen and nectar-rich plants such as vegetables and fruits. 
They also often migrate in large numbers to their favorite sources of food, which results in mass crop damage. 
When adults are disturbed or handled, they can emit an irritating chemical from their joints which can cause blisters on the skin. 
Adult beetles also have chewing mouthparts that allow them to chew through the plant material to lay eggs in the soft tissue of plants and fruit.

Are blister beetles harmful?

Yes, blister beetles can be harmful. They are known to damage crops such as alfalfa and melons by consuming their leaves and flowers. 
Additionally, some species of blister beetles have toxins in their hemolymph (blood-like fluid) that can cause skin blisters and irritation when humans come into contact with them. 
In other cases, blister beetles can infest homes and cause health problems for people who live in these affected areas. 
People should take the necessary precautions to ensure they stay away from blister beetles whenever possible.

What happens when a blister beetle bites?

Blister beetle bites are not particularly dangerous, but they can still cause biting sensations and skin irritations. 
When someone is bitten by a blister beetle, the area will turn red and swell up. 
The affected area may appear bumpy and feel hot to the touch. 
If a blister beetle bite begins to itch or gets worse over time, it might be best to seek medical attention as the bite may become infected. 
Home remedies such as baking soda paste or essential oils may also help reduce skin irritation and discomfort caused by blister beetles.

Wrap Up

From spending the early days of their lives foraging for grasshopper eggs to pupating, emerging as beetles, and wreaking havoc on crop plants, bister beetles lead an amazing life.

Their strange and unique lifecycle enables these insects to be quite hardy, surviving for more than three years as pseudo pupae under the soil.

I hope I was able to give you all the answers you needed about their life cycle, which parts of it are dangerous to humans, and more.

Thank you for reading. 

Reader Emails

In those parts of the world that blister beetles live, it is not uncommon to find their larvae or even the pupa stage in the soil.

After all, these bugs don’t hide themselves too deep – just an inch or two beneath the ground.

Some of our readers have found a beetle or two and asked us all about what it was. Read these letters and watch the pictures as well.

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