Raising Caterpillars

I often get questions about how to raise caterpillars. One of my first jobs during college was raising caterpillars, which lead to similar jobs throughout the years. Why raise a caterpillar? Not only does successfully taking care of another living thing lead to insights into its biology and behavior, but also when a beautiful butterfly or moth emerges, it is an amazing experience.

A few weeks ago I wrote a post about white-lined sphinx moth caterpillars.

whiteline caterpillar

In the update I mentioned that I had placed a caterpillar in a terrarium with moist potting soil (about five inches deep). The caterpillar immediately disappeared, but I knew where it had gone. Large moth caterpillars, like white-lined sphinx moth caterpillars or tomato hornworms, dig into the soil before pupating. Their pupa looks like a dark reddish-brown cigar. Saturday I found the moth sitting on the cloth I had used to cover the terrarium. It had successfully emerged.

Here it is.

whitelined sphinx mothwhitelined sphinx moth

Because white-lined sphinx moths are big and active, they need a lot of nectar to keep them going. After taking a few pictures, I immediately let it go. Here’s a link with some amazing pictures of white-lined sphinx moths. This entire website is full of great information and photographs.

What do you need to raise caterpillars? It does depend on what kind, but here are some general guidelines.

1. Unless you are using a kit that supplies special food, you will need large quantities of fresh plants. And not just any plant, most caterpillars will only take one or a few kinds of plants as food. Once a tiny larva has started eating one kind of plant, they often will refuse to take anything else, even if other members of its species will. A good rule of thumb is only bring home caterpillars that you are absolutely sure you know what they eat, and you have lots of those plants available to feed them. Edit: What white-lined sphinx moth caterpillars eat.

2. Provide a clean, safe container covered with screen or cloth to allow for air circulation. It is best to keep the container outside in as natural conditions as possible. Insect life cycles are extremely sensitive to light and temperature. If you bring the critter inside where it is cool and dark, it may emerge days or even weeks after wild members of its kind and may miss critical windows of opportunity to perform necessary behaviors like mate or migrate.

3. Keep only one or a few in a container. Crowding insects into small containers greatly increases the chances for disease. Insects can get viruses, bacteria and fungi, which can make them sick, just like those things can make humans sick.

Scientists have suggested that monarch butterflies may migrate because of a parasitic infection. This parasite (a protozoan) causes the butterfly to be weak but not die. By going on long migrations, the sick individuals are left behind. When we handle monarchs, we risk spreading the disease even more. Let me know if you’d like more information about this.

4. Provide sticks for butterfly caterpillars to climb on when they are about to make their chrysalises. Moth caterpillars will need plenty of moist soil to dig into. Other caterpillars may like to have different substrates to pupate in, like cloth or egg cartons.

5. Insects are also sensitive to humidity, especially when they are molting. It can be tricky, but try to keep the humidity up without getting the container too moist. Too much humidity can cause things to get moldy.

I hope these guidelines doesn’t sound too negative. Having a lot of experience, I have a better idea of all the things that can go wrong and I wanted you to avoid the problems. And oh yes  here's one more:  don't leave the lid off the container once the caterpillars have pupated. My son did this, and we had cabbage-looper moths all over the house. (It was actually a hoot!)

One great way to raise caterpillars is to plant butterfly and moth plants in a butterfly garden. (Check out an earlier post on butterfly gardening.) Then the caterpillars do all the work themselves.

Also, don't forget to take a look at some of the butterfly and caterpillars books for children.

And finally, my friend Debbie called again. Her passion vine plants now have gulf fritillary caterpillars on them (see last week’s post for details).
gulf fritillary caterpillar

132 thoughts on “Raising Caterpillars

  1. Post author

    Kate, It would help to know exactly what kind of hornworm it is. Does it look like either of these? http://msue.anr.msu.edu/news/hornworm_caterpillars_the_big_cats_of_the_vineyard Do you have any grapes or vines around?

    Since you found it on your porch, it could be finished developing and in its wandering phase looking for a place to pupate. You could try giving it a container with a few inches of potting soil and see what happens. If it immediately digs in, it was ready to pupate. If not, you might want to consider releasing it so it can find the correct plants to eat.

  2. Kate

    No it doesn't look like ether of those. I do have several vines near the porch but I have never seen a caterpillar or chew marks.
    We had some pots that we never put away and it might have dug in there. Is there a way to tell where started to pupate without disturbing it?

  3. Jane

    Hey Roberta,
    I found an almost frozen white-lined Sphinx caterpillar outside (we live in Tucson) and it gets about 37 degrees at night right now. Since I found him late in the afternoon and he was freezing to touch, I took him inside to warm up for the night. I'm worried that if I put him back out tomorrow , he won't burrow again and freeze. But if I keep him inside for the winter, and he transforms into a moth mid-winter and I release him, he won't survive due to lack of nectur. What do I do ?
    Please let me know !
    Thank you !

  4. Post author


    It is probably getting warm enough during the day for the caterpillar to dig into the soil, as long as it is still okay. Once underground, it should be fine. Or you can give it some potting soil and then put it outside in a protected place.

    I hope the caterpillar is still okay.

  5. Kimberly

    This past 2 weeks I have found 4 caterpillars on my morning glory vines. I know we get white lined sphinx moths every year so I looked up their caterpillar stage and as far as I can make out, that is what these 4 are. They range from small green about 2 inches, medium about 5 inches & brownish, and one large about 6 inches bright green one. My vines have mostly gone to seed but I'm leaving them up for the caterpillars. The small one has been eating the remaining green leaves. The morning glories started several years ago from birdseed and I cultivated them to trellises because they were pretty. What can I expect these 4 to do from here? I worry about them getting too cold at night but every morning when I check they have travelled to a new spot on the vines. What are they doing? There are not very many green spots left on the vines.

  6. Post author

    We have been having an unusually mild winter in many parts, so the caterpillars might do just fine. Also, sometimes caterpillars can finish their development early if they run out of food, which results in a slightly smaller adult. It just depends on what stage they are in.

  7. kelly

    Hey I have six white lined sphinx caterpillars, how big of a space should I have for them; one just buried underground.

  8. Post author

    Each pupa will be roughly the size of the grown larva, so you'll need enough soil for each of them, plus a pocket of soil to cushion. At least a five gallon aquarium with soil say 3 inches deep would be ideal.

  9. Sarah

    We are so excited! We have 2 tobacco hornworms that just got new homes as our science experiments. They burrowed as soon as we introduced them to their home. We are in MI. Should we expect these guys to emerge in the spring?
    Also, we have tomato leaves in there for them as well as some sticks. Do we need to keep leaves in there or since they are burrowed will they most like stay that way thus not needing he leaves?
    Thank you!

  10. Post author


    Oh, how fun for you. Since the larvae are under the soil, they are probably pupae now. They won't need any more tomato leaves, so you should remove the leaves. Removing the leaves will help prevent molds and fungi from growing, as well.

    Keep an eye on the container. The moths just might emerge in a few weeks, especially as it is an unusually warm summer. Good luck!

  11. Sarah

    Me again! Our little friends (named Lucy and Nut by my 4 and 2 year olds) are currently on our kitchen counter top. We have little shaded, not direct sun spots outside. Is it important for them to be outside or will our kitchen do ok as well? They do get some sun there. When they were in their previous form they seemed to respond to day/night changes as evidenced by their activity.
    Thank you again!

  12. Post author

    OOps, I thought I'd already responded. Yes, the kitchen counter should be fine as long as they aren't in direct sunlight. You might be seeing emergence soon.

  13. Jennifer Slaymaker

    Hopefully someone can answer my questions. I have 3 tobacco hornworms that are ready to pupate. Two of them however will dig down and then come back up. This has been going on for 2 days. Every now and then I will see what appears to be a clear fluid coming out of one of thier mouths. Is this normal? We had them in the window sill but I moved them to my closet on a shelf because I was worried they were being disturbed from various noises: kids, television, ect. Please help!

  14. Post author

    Possibilities: Is the soil too wet? On the window sill, they may have been overheating if it was in the direct sun. Also, maybe the soil isn't quite deep enough. Usually once they dig into the soil, they stay there if the conditions are okay.

  15. Sarah

    Hi Roberta!
    Bac in July we started out tobacco horn worm journey. Thinking we had for sure over or under watered their environment I was certain they were goners. We carefully dug up one of them. Just when we decided they were in fact gone it started to jump around like crazy! We very carefully and loosely buried him back up. These guys look like they're buried for the long haul. By this point are they probably going to emerge this spring? Our garage is not insulated, how and when do we help them spend their winter? It seems like they've been buried for so long!

  16. Post author


    I'm afraid there are some unknowns, but it does seem like your horn worms are in what is called "diapause" for the winter. Usually they stay in diapause approximately eight or nine months. Because they are buried in soil, they should be fine in your garage. If you want to be sure, wrap some newspapers around the container or set it into a box filled with hay or straw for a bit of extra protection. Good luck!

    A helpful discussion of the hornworm life cycle: http://labs.russell.wisc.edu/manduca/lifecycle/

  17. Lacy Trammell

    Hi Roberta! I'm so glad that I found your blog. I also found a white lined sphinx caterpillar today on my parents driveway and since I am homeschooling my kids I thought it would be a wonderful learning opportunity! He was about 3.5inches and has already burrowed himself in moist soil. Now my question is, is that I live in Texas and the temps around here right now are 75-79. Do I need to keep him cool till spring or will it be okay that he transitions into a beautiful moth?

  18. Chloe Sinclair

    I found a fat Giant Lepoard caterpillar about two weeks ago, thibking he was going to change before snow hit. I didnt realize he would hibernate. Should I give him some soil or not? And should I leave his jar outside? He seems to be quite lazy within the last week, and doesn't eat as much. Any help would be appreciated, because he is beautiful.

  19. Post author

    Giant leopards pupate above ground. They don't really make a big cocoon either, just some loose netting. If it hasn't pupated yet, try giving it some cardboard egg carton cups to hide in.
    egg carton

  20. Clare

    I have a sphinx moth. He came out of his chrysalis last night. I have him in a critter tote right now on reptile carpet. He can't fly and he's stumbling around a lot. I put some sticks in there and now he's standing on one of them with his wings dangling at his sides. I read somewhere that they eat nectar, so I made him some and put it in a leaf. He drank a whole bunch this afternoon, but he still isn't flight ready. How do I help him?

  21. Post author


    Sorry I haven't answered sooner. I've been tied up with other things lately.

    My first thought is it might be a bit cold. Moths need the flight muscles to warm up before they can fly. If its wings didn't pump up correctly before they dried, that could also cause problems.

  22. Amanda

    Hi Roberta,

    I wish I had've found your blog a couple of weeks ago! So I found 3 horn worms in my sweet potato patch a few weeks ago (we've just finished summer here in South Australia) and I thought it would be a perfect learning project for my kids to see the life cycle of (whatever moth/butterfly) larvae we found.
    I didn't realise that I needed a layer of dirt in the bottom of the tank and so just had masses of sweet potato vines and leaves in there. Then I finally found a picture that was close to what our 3 specimens looked like and realised they needed soil in which to pupate, so I added a few inches of soil and immediately they all burrowed down! But now two of them have come back to the surface and I'm worried they're not ok. I've kept fresh vines in there and the humidity seemed ok, but the soil was quite dry so I sprayed a bit of water in the tank to add more moisture. Do they build a cocoon, or would I need to know the exact type of moth to know if it would or not?

    Thanks for this amazing site, I've learned a lot already!

  23. Post author

    Sounds like you have sweet potato hornworms, Agrius convolvuli.

    The larvae do pupate in the soil. If two came back up, you might need a bit more soil. I'd take the vines out at this point, too.

    The larvae don't make a cocoon, but they do make a hollow chamber in the soil. If you were to dig them up -which I don't recommend -- the pupae should look like this pic: https://commons.wikimedia.org/wiki/File:Agrius_convolvuli_pupa.jpg

    We can grow sweet potatoes here --in fact mine are just sprouting up in the garden this week because it's spring-- but we don't have this particular insect. It does have a similar life cycle to our white-lined sphinx, resulting in a hawkmoth.

    It was great hearing from you and good luck with your project.

  24. Sarah

    Hello Again!
    Last fall we found 2 tobacco horn worms. They immediately buried themselves and started their chrysalis phase. You let me know that they would most likely winter there as they had stayed for so long. I thought for sure they were gone, but they both moved when poked (we gently dug them up to check). When will they come out? I can't give up on them now as they've made it this long! What do I do to encourage them to come out?!

  25. Post author

    Usually they need to experience the right cycles of temperature. It might be a bit early yet if you have them under natural conditions. Probably best to let nature take its course for at least a few more weeks.

  26. Juliana

    I have kept Amaryllis Borers for 2 weeks now. They stopped eating. One started crawling around really fast and non-stop as if it was looking for something. The tank we kept them in has sticks in it for them the crawl up. And I added a cup of soil in case it needs to burrow itself. Now the one crawling around disappear. I think it is in the cup of soil. Can I pour the soil out to check its status? Will it affect its growth? Which stage it is in right now? When will it pupate?

  27. Jocelyn Crow

    Hello there! I recently discovered a caterpillar out in my backyard and decided to make a home for it. This is my first time trying to raise a caterpillar since I was a kid, so I'm new with this. Not entirely sure, but with all the research I did, I am pretty positive that my caterpillar is a garden tiger moth. It recently stopped eating, and then wandered around the enclosure for awhile. I went out and when I came back home, I discovered it had buried itself in the soil I put in the bottom of the container. It chose to dig into the dirt and stay up against the side while also underneath a leaf. I can't see what's going on, and that worries me. I know some moth caterpillars will do this when they are ready to pupate, but I'm not quite sure how all of that works. I hadn't sprayed the soil for a couple days either, so it may not be damp enough. Is there anything for me to worry about or anything I should do? I would really appreciate the feedback. Thanks!

  28. Post author

    Unlike the hornworm caterpillars in this post, tiger moth caterpillars build their cocoons and pupate in the leaf litter (piles of dead leaves) at the soil surface. Yours obviously found an appropriate leaf to settle under (paper towels can be a substitute). Once the cocoon is formed, it's a waiting game. The moth may emerge in a week or so, or it may take longer depending on the temperature and lighting conditions. You don't need to worry quite so much about moisture once it has pupated, because it is protected somewhat by the cocoon. However, don't let it dry out completely. If you are really worried, it probably wouldn't hurt to gently shift some of the soil to see what it looks like.

    If you get a chance, let us know what happens.

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