Tobacco Hornworm

If you want to attract butterflies and moths, the best strategy is to grow host plants, the plants on which the larvae feed. The primary function of an adult Lepidoptera is to reproduce and the number one attractant is a place to successfully lay eggs. When nectar sources are absent from the host plant location, females will often starve to death laying eggs instead of moving off in search of food. Many moths, such as the giant silkworm moths, don’t even have mouth parts, so are incapable of eating. A garden full of chomping caterpillars is what you need if you want to see the greatest butterfly diversity.

This voracious consumer of tomato plants has got to be familiar to anyone who has ever had a garden. This is the Tobacco Hornworm, Manduca sexta, the larva form of the Carolina Sphinx moth, one of the Hawk Moths. The Tobacco Hornworm is identified by its parallel white stripes and red colored horn. The very similar Tomato Hornworm has a white “V” pattern on its flanks and carries a black horn.

There’s not much in the way of eyes here. In fact, there was no reaction at all to nearby movement or passing shadows. The larva can’t let anything slow its pursuit of nourishment. Like most herbivores, it’s not terribly effective at digesting and extracting nutrients from plant material. As a result, it has to pass a lot of plant material through its body in order to accumulate the energy necessary to complete metamorphosis.

Look at those choppers. The Tobacco Hornworm is so often seen on cultivated plants that many people have forgotten that it is a native species that was here long before we began supplying it with an easily accessible buffet. Members of the plant family Solonaceae are the primary host plants for this moth. Virginia Ground Cherry, an Ohio rarity, fits this category, but is such a small plant that it would take a small patch to grow one larva. Could this be one of the reasons for the rarity of this plant? One hornworm could consume the above ground portion of every Virginia Ground Cherry at Blue Jay Barrens. This would certainly mean trouble for the plant.

Judging by the amount eaten, this pepper plant in my garden is quite edible. Leaves, stems and fruits are all consumed. My guess is that the larva couldn’t consume the fruit as easily as the leaves, so it couldn’t take in enough to keep the body growing. With nothing left but a gnawed pepper fruit, the larva left this plant in search of another. Moving is a risky business since there’s a chance that no new host plant will be found. Fortunately, I planted a whole block of peppers, so the larva quickly found a new plant to devour. My wife loves peppers, so if she voices her displeasure at my letting the Hornworm eat two of our pepper plants, it will be evidence that she does look at this blog.