What Are These Black Spotted Red Insects on the Milkweed Plants?

While keeping an eye out for Monarch butterfly caterpillars, I keep seeing the other types of insects that feed on Common Milkweed. I wrote an article recently introducing the Milkweed Tussock Moth caterpillar. This time, I’m talking about a type of beetle that is very common on Milkweed in southern Ontario, far more commonly seen that any of the caterpillars.

Photo of Red Milkweed Beetle Horns Out On NaturalCrooksDotCom

(There are actually several different red and black insects that feed on Milkweed plants in southern Ontario. One set are beetles and the other set are bugs. I’ll have to write a post on the bugs next.)

Milkweed Beetles Have Black Spots, Long Black Antenna, and Red Shells

Aside from the vivid black and red colouring, Red Milkweed Beetles are particularly noticeable because they have long black antenna. According to a University of Wisconsin website, they are a member of the long-horn beetle family, just like the Asian Long-horned Beetle that sometimes gets in the news when areas in North America are quarantined to eradicate it. These Red Milkweed Beetles, however, offer no threat to our forests and are native to North America.

Photo of Red Milkweed Beetle Flower Stems on NaturalCrooksDotCom

Do Red Milkweed Beetles Eat the Leaves of Common Milkweed?

Yes, adult beetles do eat the leaves. The young, however, eat the roots of the milkweed plants and live underground. This is quite different from Milkweed Bugs which are an unrelated insect.

According to BugGuide.net, they have been reported on other types of Milkweed but appear to prefer Common Milkweed.

Photo of Red Milkweed Beetle Top Leaf On NaturalCrooksDotCom

Does Eating Milkweed Make These Beetles Toxic to Predators?

When insects eat the sap in milkweed plants, they take in some chemicals called cardenolides (cardiac glycosides) that are poisonous to many mammals, birds and other animals. That does not mean that a Blue Jay who eats a single Monarch caterpillar will die: the jay will feel poorly though. Many insects that eat milkweed have bright colours, like these Red Milkweed Beetles, that may help cause birds and animals to avoid eating them again to avoid a second bout of illness.

Photo of Red Milkweed Beetle Sheridan Meadow B on NaturalCrooksDotCom

The toxicity of Milkweeds, including Common Milkweed, is one of the reasons that these plants used to be classified as a danger to livestock by many jurisdictions. It was often mandatory to spray and remove Milkweed because it can poison poultry, sheep, cattle and other grazers. Now due to extensive lobbying from Monarch-lovers many places have repealed these laws so that Common Milkweed can be allowed to grow along roadsides and in private gardens.

Do I Need to Kill Red Milkweed Beetles If I Want to Help Monarch Butterflies?

Photo of Red Milkweed Beetle Up On NaturalCrooksDotCom

No. Monarchs and Milkweed Beetles have co-existed for hundreds of years. There’s no need to destroy a normal healthy part of the food web just to help Monarchs.

Why I Look Forward to my Next Encounter with a Red Milkweed Beetle

According to one article I was reading, these beetles actually make sounds including a purr and a whine. I’ll have to try to tune in the next time I encounter some!

Photo of Red Milkweed Beetle Sheridan Meadow on NaturalCrooksDotCom

Related Reading

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Have you seen some of these long-horned beetles on your local patch of Milkweed? Did you hear any of them purr? Please share your sighting with a comment.

67 thoughts on “What Are These Black Spotted Red Insects on the Milkweed Plants?

  1. They eat leaves and flowers, no flowers no seeds I’ve started to pick them off in hopes of more seeds

  2. I just saw on2 of these beetles on my milk weed. No I didnt hear them purr…

    Just didn’t know what they are or if I should give them a burial or not. Lololo

  3. I’ve been letting the milkweed grow for the Monarchs but this is the first time I’ve seen red milkweed beetles — lots of them in my yard in Iowa. Don’t hear any sounds.

    • I’ve never heard of any danger from them but you can check with your doctor. Many insects will bite if they feel threatened. I see online that it’s more common to get bitten by a similar bug called a Milkweed Assassin bug. There’s a photo of one at http://bugguide.net/node/view/428983
      I’m sorry I can’t tell you if it’s ok or not but I’ve never heard or seen anyone who was bitten.

  4. I have never had these before this year. I was concerned at first because I have dozens of them all over my milkweeds! I’m glad I found your page, I’ll be listening for purrs now!

    • They seem to do better some years than others. I’ve noticed them flying in the spring which must be how they find new plants. Thanks for sharing!

  5. First year common milkweed came up in my yard. After seeing 2 monarchs am dismayed to see these red beetles chewing the milkweed to stubs. I live in southern NJ

    • If the Milkweed has rooted in your yard, you will have quite a bit more next year. The Milkweed Beetles don’t usually out-compete Monarchs so next year you may find both! Thanks for sharing.

  6. I just encountered one of these beetles on my common milkweed plant. I’ve never seen them before and wanted to find info on them. Thank you for the info.

  7. I found one of these and they are decimating my milkweeds and a few other nearby leaves. I’m going to get rid of them….

  8. There’s one in my room in northern va! I don’t know of any milkweed in the area so this is new to me! He seems very confused haha

  9. Hi. Well I’ve just seen them for the first time, too. Detroit Michigan. And, I believe they were mating. 😏🤭☺️
    I’ve grown a small amt of scattered milkweed forever, do sightings of these guys suggest it’s a good or bad year?

  10. I’ve had milkweed plants for many years now and today I saw 2 of them. Didn’t know what they were until I read ur article and found out that they are safe. I probably have more cuz I have tons of milkweeds. Saw a few monarchs recently too so I’m glad for that.

    • Around here the Monarchs, bugs and beetles all thrive on the milkweed and it doesn’t seem to kill the plants. Hopefully it will be the same with yours.

  11. I have a milkweed beetle (July 14th S Ontario) next to poke milkweed. I also have orange milkweed in this garden. Does anybody know about this insect’s use of milkweeds other than common milkweed?

  12. I just saw my first beetle on the milkweed in my garden so I googled “red beetles” and got a bunch of Volkswagen’s! Lol… adding “insect” under “images” to my search brought me to your site. I’m in Waterdown (southern Ontario) and have never seen this beetle before. I thought it was something new and exotic…. so glad to read otherwise. Thanks!

  13. Just saw one on my swamp milkweed and initally started to panic: longhorn beetle! It didn’t help that my 600-page tome on garden insects (Cranshaw) does not have any information on it. Thank Heavens I found your page and now I can rest easy. Thank you so much!

  14. This morning while looking for traces of a groundhog family I was looking for Monarch cacoons…probably too early for that I came across one of the beetles on my dedicated milkweed patch. Was curious and googled red beetle with black spots and led me to you. No harm no foul.

  15. I live in Las Vegas, NV and my yard is filled with the orange/black speckled crawling beetle. No milkweed or much ground vegetation available. We have several trees and bushes and desert landscaping. Are these harmful or dangerous?

  16. We have them in our backyard common milkweed patch in southeastern Pennsylvania. Glad to know what they are!

      • Just found some for the first time too in Greeley, CO. Only have 4 milkweed plants, found two red beetles. I don’t believe that I’ve ever had even milkweed plants before, that I know of anyway. Someone driving by told me that they were milkweeds and that monarchs lay eggs under the leaves?? Since the beetles aren’t harmful I’ll leave them alone.

  17. I live in the city of Buffalo New York and have nurtured a milkweed patch for a few years. I’ve seen 1 or 2 monarchs near them but as of yet no caterpillars. This year I was alarmed by these red and black insects. I wondered what they were . I hosed them off and they crawled back up. Thanks for identifying and informing on the nature of co existence… plant bug butterfly. I don’t like to kill anything but I do buy lacewings and praying Mantis eggs to deal with aphids on my cherry trees…thankfully milkweed patch far from trees

    • The Monarchs get all the press releases but there are so many creatures that benefit from your milkweed. On mine, I have quite a few types of moths and butterflies visit the flowers for the nectar. Hope yours continue to thrive!

  18. I just spotted one of these Bright red beetles on a large stand of milkweed in my yard just east of Denver. I’ve been here for 16 years & it’s the first time I’ve ever seen these.
    Thanks for your article! I’ll just leave these beetles to munch away😊 I’ve seen many bugs, beetles & spiders on this milkweed, but I’ve never found any Monarch caterpillars on it😳. Do Monarchs come thru this area of the country or is it just This milkweed they don’t like? I don’t know what kind of milkweed this is. I love the scent of the flowers every year & bees go bananas for them, so I won’t ever get rid of my patch milkweed even if I never find any Monarchs. Just wondered if I should keep hoping.

  19. Found a pair mating on my milkweed. Now I have native bugs on my native plants ☺️ Thanks for the information. I’m in Pittsburgh PA. Couldn’t hear any purring tho as the birds are in full song this morning.

  20. I have been growing milkweed for several years and have been raising monarchs from egg for the last 5 years. Usually about 20 adults per year, would like to raise more, but very time consuming and I live in Southern Ontario, so a fairly short season. they start laying eggs late June, early July and are done by mid September. Sorry, off topic there a little bit, LOL, this is the first year I have seen these beetles, quite a few on my milkweed, glad I found your site, and they can live in harmony with the Monarchs.

  21. Just seen my first Milkweed Beetle today 6-69-2021. I was not sure what I was looking at, so I took a picture then found this site about these beetles. Interesting Beetle. “Mower County Minnesota”

  22. here in Central Pennsylvania I’m seeing these for the first time. Blazing fire engine red. It’s been so hot that the flowers are spent, some pods however. I’ll keep an eye out for developments. Thanks for the info.

  23. Seeing these for the first time in my yard. This is also the first year I’ve been able to identify milkweed and avoid pulling it as a weed. Noticing an uptick in the monarch population in my area as more people embrace and plant milkweed

    • I’m glad that you are seeing a few more Monarchs. The weather is sometimes a factor, too. I notice our city now adds a few milkweed plants into many of its gardens!

  24. Just had one of these on my shoulder underneath my shirt, could not figure out where this squeaky sound was coming from…. Eventually found it!

  25. First time seeing one. Was not sure good or bad bug. Now I know. But do they bite? Noise sounds? To many other stuff going on to know.

    • Most insects will try to bite if they feel threatened (bird catching them etc). So I don’t touch as I don’t want to find out! Hope you’re ok too.

  26. Thanks for the article. I saw some last year and another one today – that flew away and came back. I finally looked them up. We live in Wisconsin They weren’t in my insect books either. I’m leaving them alone.

  27. I saw these beetles for the first time today on the milkweed near my veggie garden. I live in Seward, NY. I didn’t try to touch one not knowing what they were but they did like the milkweed plants.

  28. appreciate this information I saw one of these buggers on my milkweed yesterday – wondered what it was.

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