Milkweed Beetle Bite: Is it Poisonous? Your Answer Awaits!

folder_openColeoptera, Insecta
comment1 Comment

Milkweed beetles are known for their bright colors and attraction to milkweed plants. Many people encounter these insects as they walk through gardens or nearby fields and might wonder if their bite is poisonous.

While milkweed beetles feed on the milkweed plant, which contains toxic substances, they themselves are not considered dangerous to humans. A bite from a milkweed beetle might cause some temporary discomfort, but there is no evidence to suggest that it poses any significant health risks.

Milkweed Beetle Bite: Is It Poisonous?

Milkweed beetles, such as the red milkweed beetle, are insects that specialize in eating milkweed plants. They are known for their red and black coloration, which serves as a warning to predators. But, is their bite poisonous to humans?

These beetles feed on milkweed plants that contain toxic substances called cardiac glycosides. These compounds provide the beetles with a natural defense, making them unpalatable to many predators.

  • Milkweed plants contain toxic cardiac glycosides
  • Red milkweed beetles absorb these toxins while feeding on milkweed
  • Thus, beetles are unpalatable to predators due to their toxicity

There is no evidence to suggest that milkweed beetles can bite or harm humans with their toxicity. Their main defense mechanism relies on their coloration and toxic substances to avoid being eaten by predators.

In summary, milkweed beetle bites are not known to be poisonous to humans. Their toxins are primarily used as a defense mechanism against predators and do not pose a significant threat to people.

Understanding Milkweed Plants and Their Inhabitants

Importance of Milkweed for Monarch Butterflies

Milkweed plants play a vital role in the life cycle of monarch butterflies. As the primary food source for monarch caterpillars, milkweed provides essential nutrients for growth and development. The nectar-rich flowers also attract adult butterflies to lay their eggs. Some common milkweed species found in gardens include Asclepias subverticillata and Asclepias asperula.

Milkweed Beetles and Milkweed Bugs: A Comparison

Milkweed plants host other insects too, such as milkweed beetles and milkweed bugs. Though similar, they have distinct features and behaviors.

Milkweed Beetles:

  • Scientific name: Tetraopes tetrophthalmus
  • Bright red with black spots
  • Long antennae
  • Feed on milkweed foliage

Milkweed Bugs:

  • Scientific name: Oncopeltus fasciatus (large milkweed bug) and Lygaeus kalmii (small milkweed bug)
  • Orange to reddish-orange with black patterns
  • Feed on milkweed seeds and seed pods
  • Often cluster together
Milkweed Beetles Milkweed Bugs
Color Bright red with black spots Orange to reddish-orange
Diet Milkweed foliage Milkweed seeds and seed pods
Grouping Individual Often cluster together

Milkweed plants contain a milky latex sap, which can be toxic to some insects, warding off potential threats. However, these inhabitants, including beetles and bugs, have adapted to feed on milkweed without being affected by the toxins. They even redistribute the plant’s toxins in their bodies as a form of defense against predators.

Landscaping with milkweed helps support a healthy ecosystem by providing a vital food source for monarch butterflies and hosting other fascinating insects in your garden.

Life Cycle of Red Milkweed Beetles

Egg Laying and Development

Red milkweed beetles (Tetraopes tetrophthalmus) belong to the longhorn beetle family (Cerambycidae) and are known for their specialization in eating milkweed plants. The life cycle starts with females laying eggs:

  • Near the base of milkweed plants
  • In small holes or crevices in the stems

Once hatched, the larvae start feeding on the milkweed roots, ingesting cardenolides, which are toxic compounds found in milkweeds. This ingestion helps the larvae build their own chemical defenses against predators.

Molting and Metamorphosis

As the larvae grow, they go through several instars (developmental stages) and molt between each stage. During this process, the larvae increase in size and undergo several physiological changes. When it’s time for overwintering, the larvae move deeper into the soil or the roots of the milkweed plant.

In spring, they return to the surface and complete their metamorphosis into adult beetles. The bright red coloration of adult beetles serves as a warning to predators about their toxic nature, as they have accumulated cardenolides throughout their life cycle.

Here’s a comparison of the key stages in the life cycle of Red milkweed beetles:

Stage Characteristics Feeding & Defense
Egg Laid near base of milkweed plants N/A
Larvae Feed on milkweed roots Ingest cardenolides to build chemical defenses
Overwinter Move deeper into soil or roots N/A
Adult Red with black spots/markings Retain cardenolides from larval stage as defense

Remember that Red milkweed beetles are not poisonous to humans, but their bright colors and toxic nature should keep curious individuals or pets from attempting to handle or ingest these insects.

Effects of Milkweed Beetles on Plants and Livestock

Leaf Vein Feeding and Damage to Milkweed Plants

Milkweed beetles, specifically Tetraopes spp., are known to feed on milkweed plants. Adult beetles chew the foliage, leaves, and sometimes buds and flowers, while the larvae bore into the roots and overwinter below ground1. The damage to milkweed plants can be significant, affecting the plant’s health and ability to support other insects such as Monarch butterflies.

  • Example: Red Milkweed Beetle (Tetraopes tetraophthalmus)
  • Damage: Chewing on foliage and leaves, with additional destruction to buds and flowers

Milkweed Toxicity and Animal Poisoning

Milkweed plants are known to be toxic. They contain substances like cardenolides and cardiac glycosides2. These toxic compounds can cause harm to both humans and animals if ingested. Livestock such as sheep and cattle can suffer from poisoning if they consume milkweed. Additionally, pollinators like bees and wasps tend to avoid milkweed due to its toxicity.

Milkweed Parts Toxic Compound
Sap Cardenolides, Glycosides

Prevention and Control Measures

To protect the health of both plants and livestock, it is essential to take preventive measures against milkweed beetle infestations and milkweed toxicity.

  1. Physical Barriers: Consider using gloves while handling milkweed plants to avoid skin irritation caused by sap.
  2. Remove Insects: Check milkweed plants frequently for the presence of beetles, aphids, and other pests, and remove them as needed.
  3. Fencing: Install fencing to protect livestock from grazing on milkweed plants, reducing the risk of poisoning.

Role of Milkweed Beetles in the Ecosystem

Predators and Prey

Milkweed beetles, part of the Tetraopes genus, play a critical role in the ecosystem by feeding on milkweed plants. They have a unique relationship with various insects, such as the monarch butterfly, whose caterpillars also feed on milkweed plants1. The larvae of milkweed beetles bore into the roots and overwinter below ground, emerging in late spring to chew on the foliage and leaves of milkweeds2. Predators of milkweed beetles include insects like assassin bugs and kissing bugs3.

Beetle Appearance as a Defense Mechanism

The characteristic red and black coloration of milkweed beetles serves as a defense mechanism, warning potential predators of their unpleasant taste and the presence of toxic compounds4. This protective coloration is shared by other insects that feed on milkweeds, like large milkweed bugs in the Hemiptera order5.

Here’s a comparison table of milkweed beetles and large milkweed bugs:

Feature Milkweed Beetle Large Milkweed Bug
Size Varies depending on the species About ¾” long
Family Cerambycidae (longhorn beetles) Lygaeidae (true bugs)
Predators Assassin bugs, kissing bugs Similar insect predators
Coloration Red with black markings Orange to reddish-orange with a black band
Diet Milkweed plants Milkweed plants, particularly seeds


  1. ( 2

  2. ( 2

  3. Common Milkweed Insects

  4. Bugs with Beth: Milkweed Leaf Beetle & Red Milkweed Beetle

  5. More than monarchs – What are those bugs on my milkweed?

Reader Emails

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

Letter 1 – Mating Red Milkweed Beetles


wild flowers bring the bugs!
Location: Bright, Indiana
June 28, 2011 8:54 pm
Hi Bugman, wild flowers on a vacant block in Bright, Indiana are giving me heaps of photo ops and questions as to ’What’s that bug?’ The red ’bugs’ were certainly getting busy! Bug #5 was about 1” long and reminded me of a hummingbird the way it hovered. Your site is just the best!
Signature: luv the bugs!

Mating Red Milkweed Beetles

Thanks for your compliment.  Milkweed is a very rich insect habitat.  There are insects that feed upon parts of the milkweed plant like the Large Milkweed Bug you photographed.  Many pollinating insects are attracted to the blossoms which are rich in nectar, like the Hummingbird Moth you submitted.  Our favorite of your photos, and the one we are including in this posting, is the image of the mating Red Milkweed Beetles, Tetraopes tetrophthalmus.

Thank you Daniel for helping me out with naming my bugs and posting my picture  🙂 I certainly agree with you about the Milkweed. There were 5 different insects I found that day + several types of bees buzzing around. Thank you for your wonderful site.

Letter 2 – Mating Red Milkweed Beetles: Sexual Competition for Male Domination


milkweed beetle soap opera
This series of photos might be fun for your bug love page. I found these mating red milkweed beetles in a milkweed patch near my house in Danielsville, PA. A third milkweed beetle came along and climbed on the back of the bottom bug, pushing off the top bug. They then stood there headbutting for a couple minutes, and then all three went their separate ways. I guess you could call the third one a homewrecker. 🙂 The “homewrecker” arrives and tries to push the top beetle back off the one on the bottom. There’s a standoff of sorts as the one on top from the couple refuses to back off for a few moments. But the “homewrecker” persists. The beetle on the top relents and backs off. The top beetle continues to back away from the new couple, just before the “homewrecker” decides to walk away too. … BTW, I love your site and use it all the time. I recently was able to identify a swamp milkweed leaf beetle and your site was also where I discovered the little reddish spider like creatures I had seen were wheel bug nymphs. Thanks!

Hi Johanna,
We love your account of this sexual melodrama between Red Milkweed Beetles. We do wonder though why the victor decided to relinquish his conquest.

Letter 3 – Mating Signal Flies on Milkweed


Subject:  What type of fly is this?
Geographic location of the bug:  Brantford, Ontario
Date: 07/26/2019
Time: 11:26 AM EDT
Your letter to the bugman:  Hello Bugman,
I am hoping that you can help me identify this fly. I was leaning toward a type of syrphid fly but could not find a match online. Any help would be greatly appreciated.
How you want your letter signed:  Dan

Signal Fly (left) and Red Milkweed Beetle

Dear Dan,
The image of the Fly with the Red Milkweed Beetle is an easier image for identifying purposes as it clearly shows the wing pattern on this Signal Fly in the genus
Rivellia which we determined thanks to images posted to BugGuide where it states the habitat is “on foliage, feces.”  We tried to determine if there is a relationship between Signal Flies and milkweed, and we located this BugGuide image and this BugGuide image and on The Pathless Wood we found an image and this information:  ” I did come across this interesting fly in my search, however, and later determined it is some sort of Signal Fly, a member of the Genus Rivellia. These flies are often difficult to identify from photographs alone; they are quite small, and identification depends on the presence or absence of tiny hairs called setae on the dorsal thorax, as well as the colour pattern of the wings and legs. They get their name from their patterned wings, which they tend to wave around as if signalling other individuals. I didn’t see this behaviour as this individual rested on an unopened milkweed blossom, so I was immediately taken with the unique pattern of its otherwise clear wings.”   So, for some reason, Signal Flies are attracted to milkweed, but we are not certain why.  Are there soybean fields nearby?  Your individual reminds us quite a bit of the Soybean Nodule Fly, Rivellia quadrifasciata, which is also pictured on BugGuide.

Mating Signal Flies

Hi Daniel,
Thank you for this information. There was a soybean field right next to this patch of milkweed so I think it may be safe to say Rivellia quadrifasciata is a match. I’ve seen other flies exhibit this behaviour of waving their wings around. Now I know where to start when trying to identify them.
Thanks again!

Letter 4 – Procreation of Red Milkweed Beetles


bug love
I thought I would share! Take Care,
Dundas, Ontario

Hi again Janet,
Thanks for the photo of Mating Red Milkweed Beetle, Tetraopes tetraophthalmus also called the Eastern Milkweed Longhorn. We never dreamed our Bug Love page would be as popular as it is.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts
Tags: Milkweed Beetle

Related Posts

1 Comment. Leave new

  • Chinchillazilla
    June 21, 2012 2:21 pm

    We get a lot of these on our milkweed every year. My favorite fact about these little guys (well, mostly the only thing I know) also gives me the heebie-jeebies a little – their eyes are bisected by their antennae! I was peering closely at one once and thought his antennae were growing right out of his eyeballs. At first I thought he was the victim of some horrible genetic abnormality!


Leave a Reply

Your email address will not be published. Required fields are marked *

Fill out this field
Fill out this field
Please enter a valid email address.
You need to agree with the terms to proceed