Milkweed Tiger Moth

Friday Cat-erpillar Blogging is back.

The caterpillar most associated with milkweed is the Monarch Butterfly Caterpillar. However, other caterpillars can also be found on milkweed. This includes the gregarious, Euchaetes egle, the Milkweed Tiger Moth. Like the Monarch caterpillar, the Milkweed Tiger Moth caterpillar sequesters toxins from the milkweed plant to defend against predators. Day flying butterflies can defend against bird attacks by advertising their toxicity with bright orange and black warning colors. The Milkweed Tiger Moth has bright orange warning colors on its body to warn day flying predators. However, the moth flies at night and can be attacked by bats who cannot see the warning colors. To advertise their unpalatability to bats, the moths use their sound organ to make ultrasonic clicks that are audible to bats. The “trash talking” by the moths warns bats to keep a safe distance. Nickolay I. Hristov and William E. Conner discuss this behavior in a NATURWISSENSCHAFTEN paper(Volume 92, Number 4, 164-169, DOI: 10.1007/s00114-005-0611-7).

Unlike the Monarch that lays eggs singly and caterpillars are solitary, the Milkweed Tiger Moth lays eggs in clusters and the larvae and pupae are gregarious. As you can clearly see from the pictures below, the Milkweed Tiger Moth undergoes several changes in its appearance during its development. The newly hatched first instar caterpillars have no tufts at all. The second instar caterpillars have spines but not tufts. Third and later instar larvae have full blown tufts. The older larvae sport tufts of hairs that advertise their bad taste. The tufts offer potential predators a bad tasting mouthful of hair that causes minimal damage to the caterpillar. If one caterpillar is attacked by a naive predator, the rest will be spared after the predator becomes sick from the toxins.

The pupae are fuzzy balls covered with spines. The spines can offer protection against predators such as ants and some parasitoids.

Of course, the moths look nothing at all like the earlier life stages. This exemplifies some of the problems with identification of insect larvae. If I had not grouped these together, would you be able to make a connection between a first instar larva and a third instar larva based on appearance? This is one of the reasons why entomologists are working on DNA markers. The DNA of the caterpillar is the same as in the pupa and adult. The DNA markers can allow us to connect different stages of the same insect that may look nothing alike.

Left: Gregarious First, Second and Third instar Milkweed Tiger Moth Larvae.
Middle: Late instar Milkweed Tiger Moth Larvae.
Right: Milkweed Tiger Moth Pupae

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
This entry was posted in Caterpillar Blogging, Environment. Bookmark the permalink.

43 Responses to Milkweed Tiger Moth

  1. William Louie says:

    I LOVE THE FACT THAT THEY USE “trash talk” I think was was just funny and i never could tell the difference between them

  2. Elanor Brawner says:

    Thank you for this information and the pictures. I was thinking last year that I these were the Monarch, duh. This year I will be more alert!

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  4. CollageMama says:

    I’m excited to find your blog after discovering these caterpillars in a nature preserve in North Texas. Well written.

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  6. Anonymous says:

    Each year, I maintain a large stand of milkweed for monarchs, but the entire thing was reduced to sticks this year by the milkweed tiger moth larva. They devoured the plants (even those with monarch eggs) and ate the “bark”, seed pod covers and all! I’ve been concerned for monarch populations for many years and thought the problem was other elements, but perhaps they are facing evolutionary displacement?

    • jjneal says:

      Usually those populations will cycle due to parasitoids and diseases. Where do you live that you had large populations of tiger moths? We had very low populations this year at most sites in West Central Indiana.

    • Dorothy Dunbar says:

      This morning, 7-16-2015, I destroyed from 50-75 of these tiger moth larva. And yes, I saw what destruction they could wreak! One of my plants was just a stick, with a few lacy leaves. I will go back looking for them tomorrow morning, because I know I did not get them all. If I touched them, without my jar for them to fall in, they simply rolled up and fell to the ground, where I could not get to them. Horrible little beasts!!

      • Anonymous says:

        They are just as good as the monarchs with pollination and helping creatures. Killing them is just playing god, they both have a right to live.

  7. N in VA says:

    This year I’ve grown milkweed out of concern for the Monarch population and were disappointed to find hundreds of tiger moth larvae instead of monarch larvae. Should I be concerned that they will do damage to the other plants in the garden? Do I have any chance of Monarchs laying their eggs on the milkweed? Should I just get rid of the milkweed if all it does is feed tiger moths? (Don’t want to create a ecological imbalance). For reference, we live in northern VA.

    • jjneal says:

      The Tiger Moths will only feed on the milkweed. They won’t harm the other plants. Monarch populations are just starting to build. You may have Monarchs yet.

  8. janet says:

    This morning was great. I walk every morning in the woods with my dog. I always see something amazing. This morning there were many things. First a big preying mantis sunning on goldenrod. But it was beige and its head translucent. Later when I passed by, it seemed its wings were slightly green — was this a newly emerged mantis.

    A little farther up the path is a patch of milkweed which has never bloomed but grows every year — it’s a bit shady. The tiger moth larvae were as you described — all clumped together and eating away. They were on fresh milkweed, that is not stripped yet; I did see plants that were just stalks.Thank you for the wonderful description of their behavior. I had some trouble identifying them and finally found them in A Golden Nature Guide, one of those little $1.00 books from the sixties. And I’m really glad I happened to open your website.

    At the top of the hill where there is a large path — a coyote trotting along. Of course my dog had to chase him or her. No harm to either, I think.

    Then a patch of evening primrose in bloom and little “bumblebee”-like bees in the blooms. The bees seemed drunk with joy. The pollen bags were so full of pollen they could hardly fly. They’d leave the blossom and fly sort of drunkenly and return, then sort of roll around under the stamens.

    Then, in a shady area where there was a decaying stump, a group of earthstars of all sizes and stages of closed and open. Wow.

    OK enough. Thank you again.

  9. Cece Rich says:

    How long before they go into the pupa stage? I have some in my classroom and we are impatient for the next step.

  10. jjneal says:

    It should take only a couple of weeks.
    Note: Caterpillars are sometimes parasitized and do not always produce moths.

  11. Cece Rich says:

    They are still eating but I need to get them some fresh milkweed. Thank you for all your info.

  12. Hannah says:

    I found a milkweed tussock moth at a friend’s nearby (Central Minnesota). I have been keeping it and feeding it milkweed leaves for a little over a week now. Just today, It started crawling all around the mesh habitat I am keeping it in, over and over again. I placed some sticks and fluffy grass at the bottom, thinking that might be where it would form the cocoon. But it just keeps hunting around like it’s looking for something else. Do you know of anything it would need, helpful for the cocoon stage?

  13. Marshall WAlker says:

    I live in Tennessee and the there are probably over a hundred of these on my milkweeds. should I be concerned?

  14. Two years ago when our neighbor put in his Vineyard, he took out a huge stand of native milkweed. Last year, before he could treat his Vineyard, we dug up a number of Milkweed plants growing at the edge of his field, and then transplanted them into a plot on our land – hoping to begin a new “replacement” stand. Only a few plants grew, but this year they spread to over a dozen. We also planted some in different spots on my land – various beds and the like, all in an effort to aid my State’s declining Monarch populations. I’ve been monitoring all the plants for signs of Monarchs, and today was the first day that I’ve noticed any feeding by Caterpillars. Unfortunately, upon researching what I found, I’ve determined them to be Tussock Moth Caterpillars. When I read what was written above, that they mostly eat the pods, I was taken aback. You see, one plant is entirely decimated, every leaf was eaten, but the pods are untouched – completely untouched! And yes, I’m sure they’re Tussock. I’ll post photos if there’s a way.

    Anyway, tomorrow I’m going to clean the Milkweed of any Tussock larvae I can find. I wanted these plants to replace the wild stand to help Monarchs, not to be an All-you-can-eat Buffet for some nondescript Moth. Sorry, but that’s how I feel.

    • jjneal says:

      The Tussock Moths feed on the leaves in large clusters not the pods. It is the milkweed bugs that mostly feed on the pods. Defoliation indicates a large population. Tussock moths can get parasitioids that build in large populations. Often a large population is followed by a crash the next year. The milkweeds should seed from pods. Milkweeds do best in moist soil.

    • Anonymous says:

      They have a right to live too! Just because they are less pretty doesn’t mean anything too you killing them. You really should reconsider. Plus they look so cool is late instar catterpillars.

  15. Donna Berry says:

    I have never seen the Milkweed Tiger Moth until this year. Just this week, I found them all over my buttertfly weed that I planted for Monarchs. It will be interesting to see them hatch. I just hope there aresome plants left for the Monarchs.

  16. Dorothy Dunbar says:

    I thought the Milkweed Tiger Moth had about gone, my milkweed plants are rapidly drying, but yesterday, I killed 5 Tiger Moths off it. I had better go to the front yard and check the butterfly bush. (are butterfly bushes and butterfly weeds different?) BTW, this is from W. KY, slightly East of the Lakes.

  17. 7/29/16. Planted milkweed this year in my garden Transplanted it from my son’s field. Was thrilled when all the tussock moths appeared, then realized they weren’t monarchs, and they began stripping my plants, so I’m trying to get rid of them. I took some out to a different field by milkweed, but I keep finding more and more, so now just kill them, so they won’t kill my plants. I did find one Monarch caterpillar, Hurrah! I live in southern Indiana.

  18. Holly Hunter says:

    After reading all the above entries, I’m still unsure whether the Milkweed Tiger Moths are undesirable. I want to support the Monarchs, but I like moths too! Some folks here hate them, and seem determined to get rid of them all. Should I adopt that attitude? So far, the few I have seen, are only doing minimal damage to the milkweeds.

    • Anonymous says:

      No. Both of them pollinate, and both are important ecologically. We can’t worry about one species going extinct, and not consider the other ones, at least don’t contribute to their deaths.

  19. Hello everyone, from what I understand the monarchs adults feed on nectar and the larva prefer the young leaves usually staying away from the larger leaves that the Milkweed Tussock Moth/Tiger Moth larva feed on. My caterpillars have been living side by side with no ill results.

  20. Anonymous says:

    I’ve been doing a bit of research about this moth. I’ve read quite few posts stating that the tussock moth caterpillar does not have a big negative impact on Monarch food supplies. That may often be true but my experience in Delaware is different. I have two small plots dedicated to milkweed. Last year the tussock moth caterpillars stripped every bit of growth from every milkweed plant in both plots. These plants were very large – all were more than 4 feet tall. I saw many Monarch caterpillars on the stripped plants searching for food and of course finding none. I’d like to know if there is a time of day when the Tussock moth is most active; a time when they re most likely to be depositing their egg clusters.

    • jjneal says:

      The moths are active at night. They lay eggs in clusters on a leaf and caterpillars. aggregate. If they are a problem inspect you plants and remove leaves with the caterpillars. Typically they do not reach high densities as you describe. However, large populations could be produced if environmental conditions are favorable.There are other leaf eaters on milkweed such as the milkweed beetle that could contribute to defoliation.

      • Anonymous says:

        Thanks for you prompt and informative reply. I may take steps to enclose my larger patch at night. I already have corner posts and rails to keep the plants from falling onto the yard. I just need to add screen.

  21. Sarah says:

    Hello. I’ve been raising monarchs but found a tussock and it is now in the pupae stage. From what I’ve found on the internet, it should have a furry coating but it doesn’t. It just see it looking like a little dark brown nut. Will it still develop into a moth this summer? Does it need to overwinter?

  22. Paula Knier says:

    I have had milkweed tussock caterpillars that last 2 years in my milkweed patch. Yesterday we found a moth in our bathroom and identified it as a milkweed tussock moth. It is March 15th, a little early from what I can tell. What should I do for the poor thing? It is currently hiding under the handle of my kitchen window.


    • jjneal says:

      I would release it outside or offer it to someone [perhaps a K12 student] who collects insects. It may be a look alike species. However, prematurely warm weather can put insects out of sync with the plants they need.

  23. J madden says:

    Hi, I have a question-
    How long are these milkweed tiger moths in cocoon stage??

    • jjneal says:

      Cocoons are slightly smaller than the largest larvae (around 10 mm). Pupae are covered with hairs from the larva.
      Milweed tussock moths pupae are less than one third of the size of a monarch chrysalis.

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