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Bug of the Week: Tobacco Hornworm

Add another caterpillar to Caterpillar Central from last week.

We found this brave caterpillar is feeding on a jalapeno pepper plant.

It is the tobacco hornworm, Manduca sexta, often confused with the tomato hornworm (Manduca quinquemaculata). The tobacco hornworm has straight white lines on its sides. The tomato hornworm has V-shaped markings.

It gets its name "hornworm" from the thorn-like projection at the rear of the caterpillar. The horn is not dangerous in any way. The caterpillars are perfectly harmless, except to plants.

Notice its three pairs of true legs right next to the head. The rest are fleshy prolegs.

When it finishes eating, the larva will drop off the plant and dig into the soil to pupate. The adult moth is called a hawkmoth or sphinx moth. It flies at night and isn't seen much during the day.

Tobacco hornworms are easy to raise and are great subjects for science activities with children.

The University of Arizona's Manduca Project website has a wealth of information about the life cycle, techniques for rearing Manduca, lesson plans (including cool science projects) and videos. Go check it out!

4 thoughts on “Bug of the Week: Tobacco Hornworm

  1. maryanne meehan

    I have four Tomato worms, large green ones. I would like to raise them to a moth. Any help would be appreciated. Thank you, Maryanne

  2. Roberta

    Maryanne,

    As you have probably already discovered, tomato hornworms eat a lot of foliage. You will need to keep giving them leaves until they are ready to pupate.

    When the caterpillars are ready to pupate, they will start what is called the wandering phase. They will quit eating, and start to move about the container in a way that could be described as restless. At that time, you will need to give them some soil to dig into. Clean potting soil is a good choice. Put them into a container with at least three inches of soil, enough so they can dig into it and covr themselves. The caterpillars will dig a chamber and pupate inside. The pupa will look like a reddish-brown to dark brown cigar shape.

    At that point it is basically a waiting game. Keep the soil slightly moist (don't let it dry out completely).

    See the post about raising caterpillars for a lot more details http://blog.growingwithscience.com/2008/09/raising-caterpillars/

  3. Brittany

    Hi my 3yr old found a tomato horn worm on our kitchen table that had apples and a tomato on it now their want any holes in the veggie/fruit so who knows how it got here lol well we at first thought it was a inch work till I looked it up but it was grubbing on the Apple like crazy. It then are a hole and seemed like it was making a home inside the Apple piece but it was literally almost fully rotted so I. Opened it with out touching the horn worm, and we out a price of tomato in and new piece of apple and will today it wasn't moving at all so I decided maybe it being inside was hurting it more and well then it rained and I ran out to check on it cause my daughter was freaking too and it only moves slightly if touched but barely and it's starting to turn brown/black, I feel so horrible if I killed it , is there something I can do to bring it back since it's not fully dead or is the horn worm just gone?

  4. Roberta

    Well, without being able to see it, I can't tell you for sure, but it could be two things. It could be going into the prepupa stage, getting ready to turn into a pupa. Scroll down and look for the photograph of the "prepupa" on this website: http://entomology.ifas.ufl.edu/creatures/field/hornworm.htm

    If your caterpillar looks like that, then you need to get some soil. Hornworms pupate underground in the soil. The soil should be slightly damp, but not too wet. Sort of like a wrung out sponge.

    If it looks more mushy, the caterpillar could also be suffering from a bacteria or virus infection. In that case, it wasn't anything you did.It probably will not make it.

    Hope it's a prepupa.

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