White-Marked Tussock Moth Caterpillar

2008 November 1

Here’s another very nice picture that Michelle[1] took up on Whealkate Bluff [2](the same place she found the grasshopper posted last week). It’s a White-Marked Tussock Moth caterpillar, Orgyia leucostigma, perched on a ripe wild raspberry:

I personally think this one looks very nice (If you agree, Michelle has prints of this image available here). The picture shows the back and tussocks nicely, including the red defensive glands on the back and the two long guard hairs on either side of each tussock. I think the long hairs are sensory hairs, so that if something touches them the caterpillar knows to roll up with the tussocks pointing out.

These are very distinctive caterpillars that really stand out when you find them. The general advice is not to handle them, though. The hairs are irritating, and can give dermatitis or even allergic reactions. This, of course, is how they get away with being so obvious – they are too nasty to eat.

They themselves aren’t too picky about what they eat, they apparently will take plants ranging from hardwoods like apple and birch, to conifers like hemlock and spruce. I’m not seeing any reference to them eating raspberry leaves, but I would not be at all surprised, especially since this one is obviously on a raspberry plant. In some parts of the country (particularly further south), they are reported to sometimes have major outbreaks that defoliate whole forests, but it evidently doesn’t happen here.

These are one of a number of moth species where the females don’t actually have wings. After they pupate, the females just pop out of their pupas and start giving off pheromones, and the males (who do have wings) home right in on them. Then the female (who doesn’t even come out of her cocoon) lays a mass of eggs all over herself, covered with a protective froth. The eggs overwinter, and it all starts again the next spring. Futher south the evidently have two generations per year, but here I think there is only one generation. An interesting side effect of the winglessness of the females is that they can’t actually spread or migrate by flying, so they can only expand their range as fast as the caterpillars can walk. The males can fly around, but they can’t reproduce unless they find a female wherever it is that they get to, so they can’t actually colonize any new areas. In spite of this, they are very widespread, and seem to be common throughout most of eastern North America. Since the caterpillars have to be the life stage that actually does most of the moving around, this is probably why we often see them marching along through the grass or crossing roads.

[1] In addition to individual prints for sale here,, she also has a nice 2009 calendar here.

[2] Whealkate should probably be a lot more well-known than it is, considering that it is not only a fairly prominent landmark, but actually has quite a bit of history tied up with it. It’s mentioned in Michigan’s Copper Country, by Ellis W. Courter (Contribution to Michigan Geology 92 01), as the site of the first copper mine in the Portage Lake district. The problem, though, was that it had some embarassment issues that probably kept it from getting much publicity. As Courter puts it:

The Whealkate, like most of the early mines, ended up as a dismal failure. According to Horace Stevens, author of The Copper Handbook, the Whealkate was the most unusual example of mining ever attempted in the Copper Country. He goes on to say: “The mine should be dug up bodily and preserved for engraving upon the intellect of those who would be admonished. It is probably the finest example extant of how not to do it!
The absurdity began with the first shaft which was said to have been sunk in quick-sand. It had to be abandoned due to the presence of a great amount of water. A second shaft was then sunk in the trap rock for forty feet. From that shaft, a drift was sent south for twenty feet. Then an incline shaft was sunk fifty feet. From the bottom of this shaft, a cross cut was sent one hundred feet to a supposed copper lode. A final drift was sent south for another fifty feet. In this location a winze was sunk 540 feet. These haphazard attempts did not find any copper.

20 Responses
  1. ena lee permalink
    July 26, 2009

    I have found a White Marked Tussock Moth Caterpiller on a Geranium leaf in my garden in Haddenham Buckinghamshire England. Could I be right, thought they originate in America.

  2. July 27, 2009

    They are native to America, but the whole invasive-species thing goes both ways. We have accidentally gotten a lot of things from the British Isles and Europe, and I would not be at all surprised to hear that England has gotten tussock moths from us. I haven’t been able to find any confirmation of that, though. They can be serious defoliators, it might be a good idea to contact whatever government organization oversees agriculture in your area, and ask them about it.

  3. April 20, 2010

    I see them at my elm. school.

  4. lenny & josh permalink
    June 17, 2010

    FYI we definitely have a white marked tussock moth caterpillar on our wall (York, England)

  5. Kelly permalink
    August 3, 2010

    I have photographed a White Marked Tussock Moth caterpillar in my back yard this morning, I was very surprised at its unusual appearance and managed to find out what it was through this web site: http://www.discoverlife.org.

    It was sitting on my Patio Salix that i’m growing in a pot, after reading this info I think I should try to move it before it devours my tree! Any advice??

  6. Kelly permalink
    August 3, 2010

    BTW I live in Northumberland, in a very small village.

  7. August 3, 2010

    Kelly: Just one caterpillar probably won’t do much serious damage to your tree (unless the tree is very small), but if it pupates on the tree and turns out to be female, that’s likely to be a problem. Since the females don’t have wings, they’ll lay eggs on the same tree as they pupate on, setting it up for quite an infestation in the future.

    You might want to check with your Department of Agriculture and Rural Development to make sure that they are aware that these moths are in your area.

  8. Kelly permalink
    August 3, 2010

    Hi Tim,

    Thanks for the quick response, I have informed DARD of my find and included some photographs for them, I also photographed a Wall Butterfly in my yard in early June and thought this may be of interest to them too as I am aware of the declining butterfly population.

    Thanks for the info on who to contact, it is very much appreciated and I intend to keep an eye on my yard in the future for anything else, maybe I should take a look in my garden too. I only moved into the property last October so it’s my first spring/summer here.

  9. DeAnn permalink
    March 30, 2011

    We went for one of our days in spring break to visit Dade Battlefield in Bushnell, Fl. for the day. It was covered with these caterpillars everywhere. We actually ate our picnic in the car. They where even falling out of the trees. Would have been a great adventure if it was not invested with these guys.

  10. Stacie permalink
    May 3, 2011

    My boys and I live in San Diego, California. We went to Balboa park today and found a tree covered by this crazy beautiful caterpillar. Everything that I’ve found online says they are as far west as Texas, but, surprise surprise, here they are!

  11. May 4, 2011

    Stacie: One thing I’ve noticed about insect range maps is that they are almost always too conservative and out-of-date. Which is not too surprising, because they depend on insects actually being seen by someone who will report them. I expect that these caterpillars probably got carried to California relatively recently by someone moving from further east, and now you are getting a population explosion because their predators haven’t caught up to them yet.

  12. jordan morrison permalink
    June 16, 2011

    My little 2-year- old neighbor and I found a white marked tussock moth caterpillar in my back yard. She is keeping it in a bug cage with some oak leaves. I told her that it is poisonous and can hurt her if she touches it and I made her swear that she wouldn’t touch it. should I keep it there and trust that it can live until it needs to pupate?

  13. June 17, 2011

    Jordan: If it was eating oak leaves when you found it, then there is a pretty good chance you’ll be able to get it to pupate. Just give it a couple of fresh leaves every day, and wait. If you have one of those commercial bug cages, they are pretty well ventilated so it should do OK. The fresh leaves are to provide both food and moisture, so it is important to change them every day and not leave it with partially dried-out leaves.

    I think they mostly pupate in late summer, so it might be a month or so before you get a coccoon. Then again, if you are far enough south that it is already nearly mature, it might pupate tomorrow. One can never tell.

    Their hairs do tend to be irritating to the skin, so it is good advice to tell your neighbor not to touch it, but at least it isn’t one of the painful-stinging caterpillars. Although, dealing with 2-3 year olds and caterpillars, I find that the big problem is keeping the child from hurting the caterpillar.

  14. Madison permalink
    September 11, 2011

    are these caterpillers poisonous because i have one on my wall right next to my front door

  15. September 12, 2011

    They’re only poisonous if you eat them, they aren’t one of the caterpillars that actively sting if touched. I understand their hairs could cause skin irritation if you handle them too much, but I’ve never had any problems with that myself.

  16. Keesha permalink
    May 29, 2012

    We’re in Tucson, AZ. My 10 year old just called me in to show me all of the caterpillars that are now in the garden. We have just identified from multiple websites and I’ve continued to read about them, the best website being this one. They are incredibly tiny, no hairs yet. They are all in the same small spot, and we also have found the same thing in one of our grape vines. This is the first time I’ve seen or heard of them, and I’m an active gardener. I’m hoping not much damage will be done.

  17. April 16, 2013

    Just plucked (without touching it!) a white Tussock caterpillar off my new pomogranate tree. I can’t see anymore, but is this usual for San Diego, Ca? I have never seen this little critter before. It is beautiful though. I took some nice pics of it.

  18. April 17, 2013

    Badger: According to the Bug Guide entry for tussock moths, there are several related species, some of which live out in California, and are commonly found this time of year. So you probably don’t have the same exact species as the one we have in Michigan, but it is probably a close relative.

  19. Laura permalink
    June 6, 2013

    Well, I didn’t know they were posinous… I found one and named him Henry! I hold him all the time. Until I get hurt I still will to… I love my wittle Henry <3

  20. Eliza permalink
    October 1, 2014

    I had one crawling all over me today in Northern Florida, to no ill effect. But I didn’t come into contact with its glands. Really cool bug!

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