History

Why does this insect have two names, Manduca and Hornworm?

If you have ever raised tomatoes in your backyard, you have probably seen a Hornworm. They are the big green-and-white worms that can devour a large tomato plant in a single day. Hornworms get their common name from a reddish, thorn-like structure that sticks out of the tip of the abdomen. The insect we are studying is commonly called Hornworm, but scientists refer to it as Manduca.

Scientists use a special vocabulary to name each insect they discover. Linnaeus was the founder of binomial nomenclature, the system used to ensure every insect (plant or animal) has a unique name. He devised the method of giving a species a two part name, a genus name to identify it with closely related species and a species name which is unique for the genus.

The name Manduca is the genus name and means “glutton” in Latin. The species name sexta refers to “six”. Six is an important number for Manduca because the adult has six yellow spots on either side of the abdomen. The genus and species names are always italicized, with the first letter of the genus name capitalized and the species name always lower case.

Where are Manduca from?

It is unclear whether Manduca is a native species or was brought to the colonies on tobacco plants. One report has it that ships bringing tobacco plants from Nicaragua to Virginia in 1641 introduced the insect. Another report suggests that it was already present in Maryland and Virginia.

The First Maryland Inspection Law, October 1640, states that “bad tobacco shall be judged ground [sic] leafes notably brused or worm eaten”. In other words, leaves that were partially eaten by insects, diseased, or damaged in harvesting were used as snuff or chewing tobacco.

Whether this was damage caused by the Hornworm or another insect is not clear. It is clear that by the time of the American Revolution, the moth had spread from the Tidewater colonies (eastern Virgina, North Carolina) to all tobacco growing regions. Indeed, it destroyed the crops so badly that in some areas, tobacco growing was stopped.

Where do they live?

The range of Manduca is extensive. The moth is common in the Gulf Coast states and can be occasionally found as far north as Ontario. Westward, it can be found in Minnesota and as far south as Texas. Manduca is also found in southern Arizona and in California.