Blister Beetle: Quick Guide to Identify and Manage Infestations

Blister beetles are fascinating insects belonging to the family Meloidae. They exhibit a wide range of colors, sizes, and body shapes, with their most distinctive feature being a narrow thorax and wider head, differentiating them from most beetles. These beetles are commonly known for the cantharidin toxin present in their body fluids, which can cause … Read more

Green Blister Beetle: Essential Facts and Tips

The green blister beetle is a fascinating insect belonging to the Coleoptera family Meloidae, known for its vibrant, colorful appearance. These beetles are predators of bee and grasshopper egg masses in their larval stage and feed on flowers and sometimes leaves of various plant species as adults. These beetles come in other colors such as … Read more

Desert Blister Beetle: Essential Facts and Tips for Safeguarding

Desert blister beetles are a fascinating species of insects that have gained notoriety among both scientists and nature enthusiasts. Found in arid regions such as Arizona and Texas, they are known for their distinctive narrow “neck” which contrasts with the broader head and abdomen, giving them an unmistakable appearance. These beetles can vary in size, … Read more

Iron Cross Blister Beetle: Essential Guide for Curious Minds

The Iron Cross Blister Beetle is an intriguing insect, recognizable by its striking appearance and unique defensive mechanism.

Scientifically known as Tegrodera aloga, this beetle belongs to the Meloidae family, which features other blister beetles as well.

They are known for their distinctive markings: a bright red or orange cross pattern on a dark, usually black, background.

Iron Cross Blister Beetles Mating

These beetles have an interesting defense strategy to protect themselves from predators.

When threatened, they release an odorless, colorless secretion called cantharidin. This substance is a potent toxin causing irritation, blisters, and can even be life-threatening for some animals.

These beetles inhabit dry areas and are typically found west of Arizona.

They can be found in various regions of North America, including parts of the US and Central America.

Specifically, they are prevalent in Arizona and also found in California and Sonora.

Their habitat primarily consists of grassy areas and flowering plants, where they are attracted to nectar and various flowers.

It’s essential to approach these beetles with caution due to their toxic secretion, especially when encountered in a garden or outdoor setting.

Iron Cross Blister Beetle Identification

Physical Characteristics

The Iron Cross Blister Beetle is a species known for its distinctive physical traits.

It is a medium-sized beetle with a bright red head, yellow-orange body, and black legs.

Its name comes from the dark cross-shaped markings on their wings.

Iron Cross Blister Beetle

The beetle’s body is mostly black, which contrasts with the red head and prominent black cross on their wing covers.

This distinct coloration makes them easily identifiable among other beetles.

This beetle has:

  • A soft, leathery body
  • A wide head
  • Narrow thorax
  • Large, prominent eyes

The head and thorax are wider than the visible abdomen.

Their wings don’t cover the abdomen tip completely, and their front wings are shorter compared to other blister beetles.

Biology and Life Cycle

Eggs and Larval Stage

  • The female Iron Cross Blister Beetles lay their eggs in shallow cavities in the soil during summer.
  • First instar larvae feed on the eggs of grasshoppers or bee nests.

Pupa and Adult Stage

  • Blister beetles spend winter in the larval stage and pupate in spring.
  • Adult blister beetles, such as the striped blister beetle, Epicauta vittata, emerge in early summer, with body lengths ranging between 1/3 to 2/3 inches long1.
  • During daytime, adults feed on plant parts and mate.
  • Females lay eggs again after mating, completing their one generation per year life cycle2.

Comparison table:

Stage Duration Activity
Egg Summer Laid by females in soil cavities
Larva Winter Feeding on grasshopper eggs or bee nests
Pupa Spring Development within a protective casing
Adult Early Summer Feeding on plants, mating, and laying eggs for next cycle

Distribution and Habitat

North America

The Iron Cross Blister Beetle can be found in various regions of North America, including parts of the US and Canada. Some specific states where it is prevalent include Arizona and Florida.

Central America

In Central America, the Iron Cross Blister Beetle is commonly found in countries such as Mexico. It inhabits parts of the Sonoran Desert, which spans across the US-Mexico border.

Specific Regions

  • The Sonoran Desert covers parts of Arizona, Sonora, and Mexico.
  • In the US, these beetles can be found in states such as Arizona and Florida.

The Iron Cross Blister Beetle can adapt to various habitats, including grasslands and agricultural fields where it feeds on different flowering plants.

Iron Cross Blister Beetle

Diet and Feeding Habits

Floral Preferences

The Iron Cross Blister Beetle is known for its attraction to certain flowers and plants. They are mainly found feeding on leaves, pollen, and nectar from blooms of alfalfa and other flowering plants.

  • Examples of floral preferences:
    • Alfalfa
    • Aster flowers
    • Goldenrod

Below is a comparison table between the two most common plants on which these beetles feed:

Plant Leaves Pollen Nectar
Alfalfa Yes Yes Yes
Aster Yes Yes Yes

Insect Predation

In addition to consuming plant material, the Iron Cross Blister Beetle is also known to prey on insects, particularly grasshoppers.

This makes it beneficial for reducing grasshopper populations in some agricultural settings.

Effects of Cantharidin

Impact on Humans

Cantharidin, a toxic chemical produced by iron cross blister beetles, can cause several health issues in humans when they come into contact with it:

  • Blisters: Direct contact with the beetles or their secretions can lead to blisters on the skin and painful inflammation1.
  • Digestive tract problems: Ingesting cantharidin can cause severe damage to the urinary tract and gastrointestinal lining2.
  • Eye irritation: If cantharidin enters the eyes, it can lead to pain and severe irritation.
Iron Cross Blister Beetle

Impact on Animals

Cantharidin is toxic to various animals, especially when ingested. Effects include:

  • Pests: As a defense mechanism against predators, cantharidin can be lethal to a wide range of pests1.
  • Wildlife: Animals like birds or small mammals can suffer from poisoning if they feed on iron cross blister beetles1.

Impact on Livestock

Livestock, particularly horses, are susceptible to cantharidin poisoning. Ingestion of beetles can result in numerous health issues and even death1:

  • Digestive disorders: Horses ingesting cantharidin may experience colic, diarrhea, and inflammation1.
  • Sweating: Affected animals exhibit excessive sweating1.
  • Shocks: In severe cases, cantharidin can lead to shock and even death1.

Comparison of Cantharidin’s Impact on Humans, Animals, and Livestock:

Interactions with Other Species

Predators and Prey

The Iron Cross Blister Beetle (Tegrodera aloga) belongs to the Meloidae family. These beetles have a variety of predators, including lacewings and birds.

They are also prey for other insects, such as parasitic wasps.

Influence on Gardens and Crops

Iron Cross Blister Beetles can be a garden pest, causing damage to crops like potatoes, tomatoes, beans, and clover.

Iron Cross Blister Beetle

Some examples of their impact on common garden plants include:

  • Potatoes: beetle feeding damages leaves, reduces yield
  • Tomatoes: can damage foliage, weaken plant structure
  • Beans: defoliation of bean plants, affecting growth
  • Clover: feeding on leaves causes disruption in legume growth

Comparison table of Iron Cross Blister Beetle’s impact on gardens and crops:

Crops Damage caused by the beetle Severity of impact
Potatoes Damages leaves, reduces yield Moderate to Severe
Tomatoes Foliage damage, weakens structure Moderate
Beans Defoliation, affects growth Moderate
Clover Feeding on leaves, disrupts growth Moderate

Control and Prevention Methods

Personal Protective Measures

  • Wear gloves: Iron cross blister beetles contain a toxic substance called cantharidin. Wearing gloves can protect your hands from direct skin contact.
  • Be cautious: Handle beetles carefully if needed to avoid accidentally crushing them and releasing toxins.

Agricultural and Garden Techniques

  • Soapy water: Submerge the beetles in a bucket of soapy water as an effective method of controlling them.
  • Diatomaceous earth: Sprinkle diatomaceous earth around plants to deter beetles from coming in contact with them.
  • Row covers: Using row covers can help protect your plants from the beetles without using chemicals.
  • Biopesticide: Applying a biopesticide containing beneficial organisms, such as Beauveria bassiana, can help control blister beetle populations.
Method Pros Cons
Soapy water Non-toxic, eco-friendly Manual process, time-consuming
Diatomaceous earth Safe for beneficial insects, non-toxic Requires reapplication, can be messy
Row covers Chemical-free, physical barrier May not be suitable for large-scale use
Biopesticide Targets specific pests, eco-friendly Limited availability, may affect non-target insects
Iron Cross Blister Beetle


The Iron Cross Blister Beetle, scientifically termed Tegrodera aloga, stands out with its vibrant cross pattern against a dark backdrop.

A member of the Meloidae family, this beetle has a unique defense mechanism, releasing the toxin cantharidin when threatened.

These beetles inhabit dry areas and are typically found west of Arizona.

While their appearance is captivating, caution is advised due to the potential harm from their toxic secretion, especially in gardens or agricultural settings.


  1. Blister Beetle – Texas A&M University 2 3 4 5 6 7 8 9
  2. Blister Beetles and Alfalfa | Oklahoma State University 2

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about iron cross bliser beetles. Scroll down to have a look at some of them.

Letter 1 – Iron Cross Blister Beetle

red headed yellow winged?
Location: Phoenix, AZ
April 22, 2011 11:48 pm
I saw this bug walking across the parking lot at my wife’s work.. We live in Phoenix, AZ.. It had 6 legs. I thought it looked like a giant red ant. Thanks for any and all info you have on it.
Signature: Ben

Iron Cross Blister Beetle

Dear Ben,
This is an Iron Cross Blister Beetle, and each spring we get several identification requests from their range in California and Arizona. 

Your letter is our first report for 2011, though we did receive one report in December 2010 that is most likely due to the unusual weather pattern and unseasonal rains since late 2010. 

All Blister Beetles should be handled with care as they are able to secrete a compound known as cantharidin that can cause skin to blister.

Letter 2 – Iron Cross Blister Beetle

Iron Cross Blister Beetle
Location: Chandler, AZ
May 12, 2011 9:27 pm
We saw this most beautiful bug today on our garage door. I think it’s an Iron Cross Blister Beetle. Just wanted to share the photo with you.
Love your web site!
Signature: Mary

Iron Cross Blister Beetle

Dear Mary,
Each year around this time we receive several requests to identify Iron Cross Blister Beetles that are seen in Arizona and California. 

We are happy you were able to self identify since we are currently totally bogged down with identification requests that we will never be able to fulfill.

Letter 3 – Iron Cross Blister Beetles

Invasion of the Thunder Bugs
Thu, Apr 30, 2009 at 8:01 PM
My cousin and I were riding our bikes through our subdivision in Arizona when we noticed a huge congregation of these red, yellow, and black bugs on the sidewalk next to a construction sit. It was more toward the middle of August and about 98 degrees F*.

They were pretty big, 1.3 – 2 inches long, and quite fierce looking (their coloring reminded us of a thunder/firestorm), although, even with the ultra efficient-looking wings, they didn’t fly when we came near and were actually a bit sluggish.

We did want to touch them, but, quite content with our bite-free, scratch-free, sting-free hands, we ultimately settled for a photograph. So, to cut a long story in a concise little request: we were sort of hoping you could help us identify them?
Andy and Chipi

Iron Cross Blister Beetles
Iron Cross Blister Beetles

Dear Andy and Chipi,
Every once in a while we receive a photo that we consider spectacular. We absolutely love your photo of Iron Cross Blister Beetles. These flashy beetles make appearances in Arizona and California in the spring. 

While handling Iron Cross Blister Beetles, or any other Blister Beetles for that matter, would probably not result in bites, scratches or stings, there is a very good chance it might result in blisters since the beetles secrete a substance known as cantharidin, the blistering agent.  It is also the legendary Spanish Fly, the aphrodesiac made from ground Blister Beetles.

Letter 4 – Iron Cross Blister Beetle

It’s big but what is it?
I’m out in the field in the southern Owens Valley, east of the Sierra Nevada in California, at about 4600′, and without reference materials. I’ve run across this insect that I can’t recall seeing before, but it’s fairly large (c. 3 cm in length), so

I’m surprised that I’ve not noticed it before and I’m really curious about it. See attached photo. It, and several of it’s brethren, are crawling about rather clumsily on some phlox-like flowers. Can someone identify it for me? Thank you,

Hi Jan,
This is an Iron Cross Blister Beetle in the genus Tegrodera.

Letter 5 – Iron Cross Blister Beetle

it fly’s
from tucson arizona. there are very many of these insects outside my house. please tell me.

Hi Mikie,
We haven’t gotten a photo of one of these for years. Your little beauty is a member of the Blister Beetle Family known as Iron Cross Blister Beetle, Tegrodera latecincta.

Letter 6 – Iron Cross Blister Beetle

Do you know what kind of bug is in the attached photo?
Hi, Do you know what kind of bug is in the attached photo? I found him in my yard. By the way, we let bugs – no carnage here. Your thoughts…

Hi Rita,
This is an Iron Cross Blister Beetle in the genus Tegrodera. There are at least two similar looking species with the same common name, and your specimen looks like Tegrodera erosa. Tegrodera latecincta has a more defined black cross pattern on the elytra or wing covers. There is a third species and they are found in the lower Sonoran Desert where adults feed on blossoms.

Letter 7 – Iron Cross Blister Beetle

Soldier Beetles
I recently visited your site to find out what kind of bug was in my backyard. Today I have seen at least 30-40 soldier beetles. ( I know what they are because of info and pictures on your site.)

I took some pictures of them, and have attached one because they are large files. Wanted to contribute since your site helped me figure it out. Do you know if they are harmful to cats and dogs? Just concerned because my animals play in the backyard.
Queen Creek, AZ

Hi Jo,
Somehow you have misidentified your beetle. This is not a Soldier Beetle but an Iron Cross Blister Beetle, Tegrodera latecincta. Blister Beetles contain a chemical, cantharidin, which can cause blisters on human skin. It is more of an irritant than a dangerous poison. If your cats and dogs try to eat them, they will probably have a severely irritated mouth.

Letter 8 – Iron Cross Blister Beetle

What is this bug?
This bug is just over an inch long, and I can’t find it in any of my or the library’s insect ID books.
Nick Johnson

Hi Nick,
Your letter is the fourth this week requestion an identification for the Iron Cross Blister Beetle.

Letter 9 – Iron Cross Blister Beetle

Blister Beetle
Hi bugman,
I found this guy swimming in my pool today with my kids. His colors were so beautiful and vibrant that I had to figure out what he was. I have been in Arizona my entire life and have never seen a beetle like this. Of course the kids freaked and demanded that I kill right away.

I instead gently swept the guy out the water and let him dry off. He was a very good and let me snap more 20 pictures. I have attached the better ones. I started googling for +beetle “red head” “yellow wings” “black spots” and some other variations and viola, I got to your site. However, I scared to learn that this bug is actually poisonous. Can it hurt my dog or cat? Thanks,

Hi Jeff,
Thank you for sending in your great photos of an Iron Cross Blister Beetle, Tegrodera latecincta. Blister Beetles contain a chemical, cantharidin, which can cause blisters on human skin. It is more of an irritant than a dangerous poison. In Arizona, scorpions, black widows and rattlesnakes are a greater threat to you and your pets. In the scheme of things, an unfortunate encounter with a Blister Beetle would be an inconvenience.

Letter 10 – Iron Cross Blister Beetle

different variety of Tegrodera
Found in my yard in the Owens Valley (Lone Pine), elev. 4600′, striding about quite purposefully and fearlessly. According to,
this is the true Tegrodera latecincta:

“The third and northernmost species is T. latecincta Horn, known from the Antelope and Owens valleys. ” Whereas the photos you have already posted are of Tegrodera aloga, according to the above reference. About 1.5″ long. Be all that as it may, thanks for a great site!

Thanks for the photo, information, link and correction. This is an excellent example of when location is critical for exact species identification.

Letter 11 – Iron Cross Blister Beetle

Odd insect in Saguaro Park
Dear WTB,
I took this in Saguaro National Park today, thought the pattern on the wings was unusual…any ideas?
cd krall

Hi CD,
You have taken a most awesome photo of a most awesome insect, the Iron Cross Blister Beetle in the genus Tegrodera. Your photo has the aesthetic of a safari photo of a large animal. There are several possible species, including Tegrodera aloga which is not represented on BugGuide.

Letter 12 – Iron Cross Blister Beetle

Red-headed bug with yellow spotted wings found in AZ desert
April 15, 2010
There were a whole bunch of these clinging to low plants in the parking lot at Phoenix Int’l Raceway. They were not very aggressive, but a couple did try to crawl on people, and they didn’t seem to fly. They were all gone when we returned to the truck in the dark about 10 hours later.
AZ Desert – SW Valley

Iron Cross Blister Beetle

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Red Headed Blister Beetle: Essential Facts Explained

The red-headed blister beetle (Epicauta hirticornis) is a fascinating insect with some unique characteristics. This beetle can be identified by its striking red head, soft elongated body, and the cantharidin toxin it produces. The cantharidin in their body fluids can cause blisters on human skin if mishandled, and even life-threatening inflammations in horses and livestock. … Read more