summer project

Eight-spotted Forester moth caterpillar (Alypia octomaculata)

Some of you may remember that, for a few weeks last summer, I raised Monarch caterpillars, then tagged and released the butterflies after they eclosed. I considered doing so again this summer, but we had plans to do a bit of traveling, so another Monarch rearing project seemed like a bad idea. Of course, plans often go awry, and it looks like we may not travel after all, but I’m just leaving things hanging kind of loose in case circumstances change. However, I did come up with a project that should be flexible enough that we can wander off if the opportunity arises. I’m going to collect some of the other species of caterpillars I encounter while out on my daily insects walks here at the farm. They can be kept in large containers with some of their favourite food plants and I’ll shoot some before-and-after photos of the cats and the moths or butterflies they become. If we do end up traveling a bit, I can relocate the caterpillars onto their favourite food plants, or leave cocoons or chrysalids outdoors in a relatively safe place to eclose. I’ll just miss out on a few photos.

The project should prove interesting on several counts. First, I’d like to learn more about some of the lesser-known caterpillars — such as, what they like to eat, how long it takes for them to grow before they pupate, how long until they eclose, and what they turn into. Also, most caterpillars go through some remarkable changes in colour and shape as they pass through several instars before pupating. It will be interesting to try to document some of these changes through the use of photos.

Yesterday, I collected the caterpillar below — what is, in all probability, a Virginian Tiger moth (Spilosoma virginica), often referred to as a Yellow Bear caterpillar. It was found on the tall Sweet Clover plant (Melilotus alba), which is often seen growing along roadsides. I collected a few sprigs to put in the caterpillar’s new home. I’ve recorded the date that the caterpillar was collected, and I’ll try to record the date that it cocoons. The caterpillar at the top of this post is that of an Eight-spotted Forester moth (Alypia octomaculata). I saw it yesterday morning and didn’t collect it as I hadn’t yet decided to do this caterpillar project. If I run into it or another like it, I’ll bring it back to the house.
[Edit: After reading up on the Forester moth caterpillars, it’s probably just as well that I didn’t collect this one. In his wonderful book, Caterpillars of Eastern North America, David Wagner notes:

The prepupal larvae will perish if not offered pulpy wood, dense peat balls, blocks of foam, or other materials into which they can tunnel to form their pupal cells.

In fact, Wagner mentions that caterpillars of the Subfamily Agaristinae (the Forester moths), require wood or dense chunks of peat in which to pupate and pass the winter. That really makes this group unsuitable for my summer project as I would like to stick to species with short life cycles that will be completed during the summer season. Once again, I’m reminded of why it’s so important to do adequate research and so helpful to have good field guides to consult when embarking on these kinds of projects!]

Caterpillar rearing is both fun and interesting and would probably make a great educational project for a young person (or any person for that matter). It does take some work each day while the caterpillars are feeding and growing. Fresh plant materials must be gathered, and the caterpillar container must be kept reasonably clean. However, it’s not that time-consuming and the results are usually worth the work.

Virginian Tiger moth caterpillar (Spilosoma virginica) – often referred to as a Yellow Bear.

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16 Responses to “summer project”

  1. threecollie Says:

    I am delighted to have you identify the little yellow caterpillar. I see them all the time, but had no clue what they were. Thanks

  2. Marnie Says:

    I’m raising a couple of Monarch caterpillars right now. It’s my first time, so I’m grateful for your experiences and those of others I’ve read online. The “babies” are about four to five days old right now, and growing nicely. Wish us luck! I hope your new project works out well.

  3. Laura Says:

    Sounds like a fun project and one I’ll have to follow along with.

    I wish I had *kept* the black swallowtail cats I found on my parsley plants – they disappeared just as soon as they seemed big enough to make their cocoons – I’ve searched plenty but can’t them.

  4. robin andrea Says:

    Oh this is going to be so much fun! I can’t wait to see what these emerged creatures will look like. Such a great project, and you have so much patience. I’m looking forward to the reports.

  5. Ontario Wanderer Says:

    Great photos. We did the Monarch raising project last summer after hearing about yours and had chrysalises to show during our annual art show.

  6. Wayne Says:

    Bev – Great find on the eight-spotted forester caterpillar! I think I’ve mentioned that the adult moth was one of the first that I’ve identified, but I’ve never seen the caterpillar. It is quite a festive one.

    What plant did you find it on?

    I had it tagged as feeding on grapevine (muscadine, around here, of which we have plenty and so see lots of moths) but also as Virginia creeper and Peppervine.

  7. bev Says:

    threecollie – There are a couple of other common yellow caterpillars, but if the ones you see have very long hair like this one, it’s likely a Virginian Tiger Moth (Yellow Bear) as they are quite common. The moth is mostly white. I’ll post photos of this one when it emerges.

    Marnie – Good luck with the Monarch caterpillars. No doubt, you’ll enjoy watching them grow and become butterflies. I learned a lot about the caterpillars last year while we were caring for quite a few.

    Laura – Black swallowtail caterpillars are beautiful. They’re also very good at hiding as they make their chrysalis. I’ve found that most caterpillars try to wander away from their food plant to find a safe hiding spot when they are ready to pupate, so do look around at least a few feet away.

    robin – I’ll definitely post follow-up photos of the moths and butterflies as they emerge. As for the patience, it seems I may not have to wait too long. The Yellow Bear caterpillar made a cocoon yesterday, and if I recall correctly, the last time I kept one of these it was something like 9 days until it emerged as a moth. Some will definitely take longer – in fact, see my note to Wayne down below. At the moment, I’m planning to collect mainly those species that will complete their life cycle in a few short weeks. I’ve always wanted to try raising the large silk moths that pupate over winter, but that requires a level of patience that I probably don’t have! (-:

    OW – Thanks! I’m glad you were inspired to give the Monarch raising a whirl. It really is quite a learning experience.

    Wayne – Yes, it was a neat find, but now I’m a little sorry that I didn’t walk back to collect the caterpillar later in the day. It was beautifully marked. One thing that I find so striking about this species is its close resemblance to another moth’s caterpillar — the Pearly Wood Nymph moth Eudryas unio. I always puzzle over such resemblances and wonder what they mean — why one looks so close to another and whether the markings are meant to be cryptic on a certain plant, or if they are meant as a warning. In this case, after reading David Wagner’s Caterpillars of Eastern North America, it appears that the markings are a warning. He mentions that Forester larvae “are quick to vomit and orange, mostly clear fluid when disturbed.” He also mentions that all of these similar looking caterpillars often rest exposed on or near new foliage, which he comments “suggests that they are chemically protected.” Interesting (to me) is that the moths look nothing alike, even though the caterpillars are rather similar in many ways.
    Regarding the food plant, oddly enough, I found the forester caterpillar atop a milkweed plant. As you’ve noted they eat grape and virginia creeper, so I can’t imagine what it was doing on the milkweed. It’s probably a good thing I did not collect this one as I wouldn’t have thought to look at Wagner’s notes on pupation (this being a reminder to myself that, in future, I must do so with all caterpillars that I can find in his book):

    The prepupal larvae will perish if not offered pulpy wood, dense peat balls, blocks of foam, or other materials into which they can tunnel to form their pupal cells.

    In fact, of the whole Forester Moth group (Subfamily Agaristinae), Wagner mentions that the prepupal larvae require wood or dense chunks of peat in which to pupate and pass the winter. That makes all of them poor candidates for my summer project!

  8. DougT Says:

    Sounds like a wonderful project. Though I can’t entirely agree with the not too time consuming part. We have just induced egg laying in a half dozen wild-caught silver bordered fritillaries. We have over 500 eggs and will be rearing up the larvae as part of a restoration project. I’ll blog about it eventually. When you are dealing with numbers that large, sanitation becomes a critical issue, and the whole process becomes very time consuming. I hope that you enjoy, and continue to blog about, your caterpillar project. We’ll have to get you one of our “Frass Happens” refrigerator magnets.

  9. bev Says:

    Doug – Yes, raising 500 larvae is a lot different than 50 or so Monarchs. The amount of frass produced each day would be.. well.. awesome! There will be plenty of maintenance involved in your project. I found 50 Monarchs quite enough for me last year. I kept them in several group containers and took each one outside almost every day, placed the caterpillars on fresh milkweed leaves, while tossing out the old leaves and washing and drying the containers, then placing everyone back in the containers. I’ll bet the process took up at least a half hour every morning, and that didn’t include the milkweed leaf collecting, or searching for eggs and early instar larvae. Yes, plenty of work once you get beyond a half dozen larvae — so just a word of warning to those reading this comment – don’t go overboard with caterpillar raising unless you’re committed to the work that’s required.

  10. Marnie Says:

    Oh no. I just brought in a third wee caterpillar, maybe one or two days old, and my biggest caterpillar … ate it. Just scarfed it down as if it were starving (despite a constant supply of fresh leaves). It sensed the newcomer right away and “ran” over to it.

    I thought I’d read a lot about rearing Monarchs, but I must have missed the part where they’re cannibals. Jeez. I guess they want to protect their own territory/food supply? That’s the last one I bring in. (I say that every time …) :(

  11. Marnie Says:

    OK, I just found a posting about this on the monarchwatch forum. Sigh, wish I’d read it earlier!

  12. bev Says:

    Marnie – That’s quite an interesting observation. I have to say that I’ve never seen this happen before, but obviously it happens enough that others are writing about it on MonarchWatch. When I kept Monarchs last year, most of the time I kept them separated into groups that were about the same age. Eggs in one tray, very tiny cats in another tray, mediums in another, and the really large ones getting close to the time to pupate were in separate jars with a piece of screen over top. That was mainly because I didn’t want to lose the small ones when I was changing the leaves and cleaning their containers, etc… but also, it helped me to keep track of everyone and where they were at in their development. Yes, do some reading up on raising Monarchs. I found it fairly easy, but as mentioned above, there’s quite a bit of maintenance involved, so I’d advise most people to stick to raising just a small number.

  13. Pamela Says:

    The Eight-spotted Forester Caterpillar is beautiful–great find. We had so many of these moths around here earlier this season that I’ve been thinking I’d get to see a caterpillar or two, but so far no luck. We have lots of grapevine, lots of foliage for caterpillars to hide in, so perhaps its not surprising. I was surpised to read that you found this one on a milkweed

  14. Nina Says:

    I like the eight-spotted caterpillar. I found and eight-spotted moth (yes, on milkweed) and loved his orange knees! Such a pretty , sharp little moth.

  15. bev Says:

    Pamela – This was the first of these caterpillars that I’ve found here at the farm, although I have seen the moths in previous years. Caterpillars are often hard to find as they’re usually underneath leaf cover. I was also surprised to find this one sitting in the open on top of a milkweed.

    Nina – Yes, they really are a beautiful little moth, aren’t they?

  16. Kathi Says:

    Hi, I found your blog while trying to put a name to a caterpillar I just found and photographed. From the small drawing in my Golden Guide to Butterflies and Moths, I thought it might be an Eight Spotted Forester, and comparing it to your photo, I find I was right. Cool!

    Mine was climbing the vertical support post of my gazebo; there are volunteer wild grapevines there, so I assume that is what he was eating.

    Thanks, an I like your blog,