Tobacco Hornworm

Manduca sexta (Linnaeus) (Insecta: Lepidoptera: Sphingidae)

You can tell the difference between the tobacco and the tomato hornworms by the markings on the side, V shaped are for the tomato hornworm that likes to eat tomato vines and the straight lines are for the tobacco hornworm. Also the horn on the hind-end of the tobacco hornworm is red, which is the color of mine. I am letting my grandkids save these caterpillars for pets and see if we can watch them turn into pupas and hatch into moths next spring.

I was checking out my tomatoes and saw these little balls of bug poop. For a bug the poo-balls were huge, at least 1/4 inch in width. I didn't see a butt-hole on this caterpillar, so I wonder which end they poop from? With all that munching and eating some of the food is not used and needs to come back out. That part is called frass, or as you may like to call it, poop.

Unlike the dreaded Cabbage moth that lays lots of eggs, the hornworm moth called, believe it or not, the spectacular Sphinx Moth, which has a 4-6 inch wingspan. This beautiful moth only lays a few eggs here and there. But one hornworm unchecked can eat a whole tomato plant so fast it'll make your head spin. That's why I go and check every other day. I usually pull the caterpillars off my garden plants and feed them to my chickens. Even though the hornworm emits through it's hind-end a green liquid that taste awful as a deterrent. The chickens gobble them up like candy.

I knew immediately before I saw my tomato vines de-leafed I had a hornworm infestation. For as big and spectacular as these caterpillars get, some reach 3 inches in length, the moth is bigger and beautiful. I have a link at the bottom of my article that is used for references and some of the pictures I used in this article. The larger photos are taken with my iPad camera.

Tobacco and tomato hornworms are common, large caterpillars that defoliate tomato plants. Their large size allows them to strip a plant of foliage in a short period of time, so they frequently catch gardeners by surprise. They are quite similar in appearance and biology.

The larva is cylindrical in form and bears five pairs of prolegs in addition to three pairs of thoracic legs. The most striking feature of the larva is a thick pointed structure or "horn" located dorsally on the terminal abdominal segment. The tobacco hornworm develops seven straight oblique whitish lines laterally. The white lines are edged with black on the upper borders, and the "horn" is usually red in color. The tomato hornworm is superficially similar, but instead of the seven oblique lateral bands it bears eight whitish or yellowish "V"-shaped marks laterally, and pointing anteriorly. The "V"-shaped marks are not edged in black. Also, in tomato hornworm the "horn" tends to be black in color. There normally are five instars, but occasionally six are observed. Corresponding mean larval body lengths are 6.7, 11.2, 23.4, 49.0, and 81.3 mm, respectively. Larval development time averages about 20 days.

The Tobacco Hornworm

Pupa: Mature larvae drop to the soil at maturity and burrow to a depth of 10 to 15 cm, where they form a pupal cell. The pupa is large and elongate-oval in form, but pointed at the posterior end. It measures 45 to 60 mm in length. The pupa bears a pronounced maxillary loop, a structure which encases the mouthparts. The maxillary loop in tobacco hornworm extends back about one-fourth the length of the body, whereas in tomato hornworm it is longer, usually extending for about one-third the length of the body. The color of the pupa is brown or reddish brown. Duration of the pupal stage is protracted and variable.

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