Invertebrates
Tobacco Hornworm
Manduca sexta · also called tobacco hornworms
A tobacco hornworm munching steadily through a tomato leaf carries small white lumps studded across its back, harmless-looking decorations that are actually the cocoons of parasitic wasps quietly sealing the caterpillar’s fate.
Overview
The tobacco hornworm, Manduca sexta, is a large, striped caterpillar found on tobacco, tomato, and other nightshade plants across grassland and agricultural habitat throughout the Americas. Its status as one of science’s most important laboratory model organisms, vulnerability to visible parasitic wasp cocoons, and powerful hovering adult moth form make it one of the more scientifically significant and ecologically interesting caterpillars most gardeners will encounter.
A caterpillar that became a scientific icon
Few insects have contributed as much to laboratory science as the tobacco hornworm, whose size and well-studied biology have made it a go-to subject for research questions having nothing to do with tobacco or tomatoes at all.
Status
Least Concern — widespread and abundant across suitable habitat throughout the Americas.
Tobacco Hornworm: common questions
How can you tell a tobacco hornworm from a tomato hornworm?
The tobacco hornworm shows seven diagonal white stripes along its body and a reddish horn near the tail, while the closely related tomato hornworm instead has V-shaped markings and a black horn, differences that let gardeners and researchers reliably tell the two similar-looking species apart.
Why do scientists use the tobacco hornworm so often in research?
This species is valued as a laboratory model organism because of its large size, which makes it easier to study and manipulate, combined with decades of accumulated scientific understanding of its physiology and neurobiology, making it a convenient and well-characterised subject for insect research generally.
What are the white lumps sometimes seen on a tobacco hornworm's back?
These are the cocoons of parasitic braconic wasps whose larvae have already fed inside the caterpillar and emerged to pupate on its surface, a sign the caterpillar has been parasitized and will not survive to become an adult moth.
What does the adult tobacco hornworm moth look like?
It becomes a large sphinx moth capable of powerful, sustained hovering flight at flowers, a flying style similar in appearance to a hummingbird's, making the adult stage a genuinely impressive flier compared with the relatively slow-moving caterpillar it started out as.