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Insects Commonly Found on Milkweed 101

2/7/2019

13 Comments

 

We all know that monarch larvae eat milkweed plants, but what about the other insects that share a food source with Monarchs?

The truth is, most of these insects serve a purpose within their respective ecosystems. The reason that many of them are black and orange like Monarchs is that they use the same defense mechanism called "aposematism" where their black and orange coloration warns predators of their toxic/bitter taste caused by cardiac glycosides which they acquire from milkweed.

​Learn how to identify these insects and find out if they are harmful or harmless to Monarchs! 

Red Milkweed Beetle (Tetraopes tetrophthalmus)

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Native range: Their range matches the distribution of Common Milkweed (Asclepias syriaca), basically the Northeast quadrant of North America

Harmful to Monarch caterpillars/eggs? No. They are herbivores and only eat milkweed. They are harmless to monarch larvae and eggs so you can leave them on your milkweed plant if you have enough to go around.

Identification: Red/orange in color with oval spots all over body and un-ringed antennae.

​Life Cycle: Eggs laid on stems near ground or just below surface; larvae bore into stems, overwinter in roots, and pupate in spring; adults emerge in early summer

Small Milkweed Bug (Lygaeus kalmii)

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Native range: Throughout US and Southern Canada

​Harmful to Monarch caterpillars/eggs? Sometimes. They are mostly herbaceous and will suck nectar from flowers and sometimes feed on milkweed seeds. However, they have been reported to be predators, especially in spring when milkweed seeds are scarce. They have been reported feeding on honey bees, monarch caterpillars and pupae, and dogbane beetles, among others (Root 1986). The best method to remove the bugs from your milkweed plant is to grab them and throw them into a bucket of soapy water. 

Identification
They adult is black with a broad orange/red band on forewing, forming an "X" shape. Their head is black with a dull red spot on top. In eastern specimens, forewings are all black, but in western specimens they have large white spots. (Bugguide.net)

Life cycle
Eggs are laid on milkweed in spring. One or more generations per year. Adults overwinter.



Large Milkweed Bug (​Oncopeltus fasciatus)

Picture
Native range: Throughout North America and from Central America through Mexico and the Caribbean to southern areas in Canada.

Harmful to Monarch caterpillars/eggs? No, they do not feed on Monarch larvae or eggs so they are harmless and play a role in the ecosystem. However, they do feed on the seeds, leaves and stems of milkweeds (Asclepias). Damage to the plants can deplete resources for Monarch caterpillars. Planting more milkweed will ensure that they both have enough to eat.

Identification: Adults are overall black and orange- with black band in the middle and two large black spots in front and back.  Nymphs are bright orange and develop black spots late. 
​
​Life Cycle: Eggs are laid in milkweed seed pods or in crevices between pods. About 30 eggs are laid a day, and about 2,000 over a female's lifespan, which lasts about a month during the summer. One or more generations per year. They can't survive cold winters, so they migrate south in the fall. They overwinter in the southern Atlantic and Gulf coast states where they feed and breed and gradually migrate north again in the spring and summer. (bugguide.net)

Swamp Milkweed Leaf Beetle (​Labidomera clivicollis)

Picture
Native range:  Widespread in North America east of the Rocky Mountains, south to northern Mexico (Riley et al. 2003)

Harmful to Monarch caterpillars/eggs? Technically, no, because they are herbaceous. However they do feed on milkweeds, especially Swamp Milkweed (Asclepias incarnata), but also Common Milkweed (A. syriaca). To control populations from eating all of your milkweed, you can pick them off and put them in a soapy bucket of water. 

Life Cycle: They often overwinter as adults among leaves such as mullein (Verbascum). Adults mate on or around milkweed. Eggs are cemented to the underside of leaves. Larvae feed on leaves, and drop to ground to pupate (National Audubon Society Field Guide to Insects and Spiders)

Note: Unlike the Monarch, larvae and adults of the milkweed leaf beetle are not thought to sequester cardiac glycosides from their milkweed host. 

Resources

Large Milkweed Bug Profile
https://bugguide.net/node/view/504

Missouri Botanical Garden
http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/plant-bugs/milkweed-bugs.aspx

Milne, Lorus and Margery. National Audubon Society Field Guide to Insects and Spiders
Knopf, 1980.

Red Milkweed Beetle Profile 
https://bugguide.net/node/view/2966

Small Milkweed Bug Profile
https://bugguide.net/node/view/460#range
13 Comments
Kathy Cullen link
4/21/2019 03:49:06 pm

So interesting! My customers often ask me if the milkweed bugs will harm their monarchs or milkweeds, and what is the difference between bugs. I didn't realize some of the milkweed bugs looked so similar but would behave so differently. Thank you!

Reply
Rebecca
4/22/2019 07:55:03 am

Glad you found it helpful. Thank you for reading!

Reply
Elizabeth R McDonell
11/15/2019 02:55:27 pm

Thank you for the information. Now I finally know what they are.

Reply
Jodi Reinschmidt link
4/26/2020 10:05:47 am

Help

Reply
Susan Greenlee Mamon
6/10/2020 07:41:14 am

I had an infestation of large milkweed bugs. Pulled up all of my milkweeds. More have now come up, and the bugs are back. How can I get rid of the bugs without harming the monarchs? I live in central FL.
Thank you . Susan

Reply
Carter Andrea
6/13/2020 09:11:19 am

I use Neem oil on the young milkweed bugs. I just spray at little on the infestations. I check for them every day. I also squish the adults. You have to be vigilant but eventually you will get them under control. Otherwise the milkweed ends up not flowering...

Reply
Me
9/30/2020 08:53:45 pm

Wouldn't neem oil also kill the butterflies?

Sybil Snowden
7/3/2020 11:15:28 am

I've had milkweed and monarchs for a few years and this is the first year we've had a few Swamp Milkweed Leaf Beetles eating the milkweed. When should I be concerned? I don't want to wait too long but I also don't want to eradicate them if they are only a minor nuisance. I'm in Houston, TX.

Reply
Bill Beebe
7/30/2020 06:15:31 pm

I found 3 rows of 5 blue eggs on the underneath side of a common milkweed plant, and have been unable to figure out what they may be.
Does anyone have any ideas?
Thank you.

Reply
Karen Coffman
8/6/2020 05:25:49 pm

I saw on a YouTube video that A butterfly was laying the blue eggs I believe they might’ve been monarch not for sure.

Reply
Laurie McDowell
8/17/2020 05:59:34 pm

The milkweed bugs denuded the milkweed of all its blooms, and there is nothing left for the monarchs. Do I need to implement control measures next summer?

Reply
Kristi Bennett link
10/13/2020 08:43:21 am

In Iowa, and this is the first year I had multiple milkweed plants. It’s also the first year I had an infestation of MANY (large?) milkweed bugs. Out of the 10 or so plants, the bugs ruined/dessicated/blackened the seed pods on 5 plants; the others had some foliage/distance and weren’t attacked much. I had at least 5 monarch caterpillars in June, but they suddenly all disappeared within a day or two. After that, more and more bugs - often two generations at once. I would knock off and spray with hose, but didn’t deter them. Next year, the soapy water bucket comes out! (They are good at scuttling under leaves if they see you, though)

Reply
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10/15/2020 09:11:45 am

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    Author

    Rebecca Chandler
    Garden Educator, Naturalist and Ethnobotanist

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