three caterpillars

On Saturday, while out for my evening walk, I checked Common Milkweed (Asclepias syriaca) leaves for signs of caterpillar feeding. In just one small area of a meadow, I was able to find three different species of caterpillars. I collected three leaves to create the above photograph (click on all photos for larger views). From left to right, the caterpillars are the Milkweed Tussock moth (Euchaetes egle), the Dogbane Tiger moth (Cycnia tenera) and the Monarch butterfly (Danaus plexippus). I believe the two moth caterpillars are probably still a molt away from being final instars, at which stage they would cocoon. The Monarch caterpillar is just a third instar, so has a couple of more molts to go before it will form a chrysalis.

If you’re interested in studying caterpillars, this is an excellent time of year to do so. Most moths and butterflies will have laid their eggs awhile ago. The resulting generation of caterpillars will be busily feeding in order to attain their full size before pupating. Smaller caterpillars will create holes in leaves, while larger ones will often eat away a good part of the leaf as in the above example. Very large caterpillars such as the Cecropia, will actually eat so many leaves that a tree branch may become conspicuously bare. That’s how I’ve managed to find them in the past — by watching for branches that are without leaves.

Some of you may remember that I recently wrote about Dogbane Tiger (Cycnia tenera) moths. They were the delicate white moths with yellow along their wing edges. Above is the larva — a furry gray caterpillar. According to this page from Wikipedia, there can be several generations of Cycnia tenera in most ranges, so caterpillars found now might cocoon and emerge this season. If I see any more, I’ll probably collect one or two to rear.

The Milkweed Tussock moth (Euchaetes egle) caterpillar is one that we frequently see around the farm from this time onwards. The one in the above photo is a final instar photographed in 2004. Notice how it has more white tufting than the caterpillar in the top photo from August 5th. Caterpillars often look quite different at each successive molt. Some species have different colours, or length of setae (fur-like covering), or they might have antennae or horns, or some other distinguishing feature. The variation between instars is one of the things that makes it a little challenging to identify caterpillars, especially the early instars of each species.

I often find the younger instar Milkweed Tussock caterpillars feeding together as in the above photo. If alarmed, the younger instar caterpillars will thrash about wildly in an attempt to repel potential predators. According to this page also from Wikipedia, there is only one generation of these caterpillars in the north This moth would overwinter in its cocoon, making it one that I won’t be collecting as I don’t wish keep any pupae through until next spring.

So, if you want to see some caterpillars, get out walking about the fields and woods, turning damaged leaves and watching for conspicuously bare branches. You’re bound to find at least one or two.

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13 Responses to “three caterpillars”

  1. threecollie Says:

    I simply love your caterpillar identifications. We see many of these all the time, but have no clue…thanks for the education!

  2. Cathy Says:

    Those Tussock Moth caterpillars look like pipe cleaners run amuck. This is so neat. I went back to my milkweed leaf per your instructions and took another picture. I’m not sure if what I’m seeing is ‘cooked’ eggs or the next phase in development. I’ll keep checking.

  3. robin andrea Says:

    Yes, Cathy hit on exactly what I was trying to connect with the Tussock Moth caterpillars, they do look like pipe cleaners. What a great description. I’ve been looking under leaves but so far not finding much. You inspire me to keep on!

  4. bev Says:

    threecollie – It’s always kind of nice to be able to put names to creatures and learn a bit about their natural history, isn’t it? (-:

    Cathy – Yes! Wild looking pipe cleaners! As for those eggs, yes, keep checking. They might be eggs of some species of moth or butterfly. Unfortunately, I’m not very knowledgeable about insect eggs. I figure out most things just by watching them. Just keep checking and shooting the odd photo and you’ll probably discover what species they belong to!

    robin – Perhaps your weather has had an effect on the insect life this year. However, I’d keep on watching for awhile. From my travels in the PNW, I know that the season is longer, so things may be running a bit behind where they are here in my area. Regardless, I’m sure that you’ll eventually find caterpillars of some kind on the wild plants.

  5. Nina Says:

    I’m glad to see your Milkweed Tussock cats all together like that. I came across one leaf (in our huge milkweed patch) that was hanging low and found about 30 nestled together. I thought it odd that with an entire field to feed from, so many would gather in one spot!

  6. bev Says:

    Nina – That’s normal for that species. They’re one of the “social” caterpillars that like to hang out together while they’re still small. It’s a form of protection as they do a sort of group thrashing about when anything comes too close. As they get larger, they will wander off and feed on their own. In my area, we’re at about that stage where I’m finding solitary caterpillars now.

  7. Wren Says:

    I love the photos. You’ve inspired me to go outside and look for caterpillars.

  8. DougT Says:

    Milkweed tusscok moths have one of my favorite caterpillars. Of course, a lot of the insects that feed on milkweed have great colors. It’s good to be toxic.

  9. Mark Says:

    I was surprised to count 12 monarch caterpillars in a area of a couple square feet of milkweed this past weekend. This find and your photos make me want to go find more.

  10. Wayne Says:

    We see milkweed tussock caterpillars around here too. Oddly, we have very few traditional, milk-sap milkweeds in the immediate area – probably because of the extensive shade, and deer encroachment. What we do have is anglepod, a milkweed vine, that grows very well in shade and since it climbs is relatively resistant to deer predation. It doesn’t have milky sap though, and I’ve never seen a monarch on it. Milkweed beetles, yes, and tussocks, yes.

    I’ve been watching our various wild mints – Teucrium canadensis in particular. Yesterday I found four distinct species of flower and jumping spiders, very very tiny, on them. Time for some more photography!

  11. bev Says:

    Wren – I think this is the best time of the year for caterpillar watching, so I do hope you find some!

    Doug – Yes, you’re so right about the colours of the insects that feed on milkweed. I’ve been enjoying watching Milkweed Longhorn Beetles for the past while and they are certainly bright and beautiful!

    Mark – Those are super numbers to find in a small area of milkweed. Usually, the predators manage to wipe out most of the caterpillars, so you would be lucky to find a couple. The season is so short that it’s good to make the best of it and do as much observing as you can before it’s over.

    Wayne – Interesting that the tussocks and milkweed beetles are on the anglepod, but not the monarchs! There must be something about it that just doesn’t cut it for the monarchs. hmmmm.
    I hope you can get some photos of the spiders on the mint. I should be out doing more looking, but this summer’s heat and humidity seems to be bothering me a good deal. However, today’s forecast is a little cooler, so I must get out and spend part of the day looking for insects and spiders.

  12. Marcia Bonta Says:


    Now that we have DSL again, I can resume reading my favorite blog. I am hopeful about dogbane tiger moths because we have lots of dogbane. All your research and your super photos are a great help to me. Thanks.

  13. bev Says:

    Marcia – Thanks for the kind words. Good to hear that you have your DSL again! As you may have read on my blog, I’ve just recently set up a new outdoor modem that gives me a much better connection that my very slow dial-up service. I’m finally able to visit more of my favourite blogs. It was painfully slow before and I just didn’t have enough time to sit around waiting for pages to download.