Tobacco Hornworm

Description:

Commonly known as the tobacco hornworm, it is closely related to and often confused with the very similar tomato hornworm (Manduca quinquemaculata); the larvae of both feed on the foliage of various plants from the family Solanaceae. The larvae of these species can be distinguished by their lateral markings: tomato hornworms have eight V-shaped markings while tobacco hornworms have seven diagonal lines.[2] Furthermore, the caterpillars can be distinguished from the larval stage onwards by the color of the horns on their back ends: M. quinquemaculata caterpillars have black horns, while M. sexta caterpillars have red horns. M. sexta has a short life cycle, lasting about 30 to 50 days. In most areas, M. sexta has about two generations per year, but can have about three or four generations per year in Florida. M. sexta larvae are green in color and grow up to 70 millimeters in length. Under laboratory conditions, while fed a wheat-germ based diet, larvae are turquoise due to a lack of pigments in their diet. As vitamin A and other carotenoids are necessary for the visual pigments (rhodopsin,) an artificial diet-reared hornworm may have poor vision due to lack of carotenoids in the diet. During the larval stage, M. sexta caterpillars feed on plants of the family Solanaceae, principally tobacco, tomatoes and members of the genus Datura. Near the end of this stage, the caterpillar seeks a location for pupation, burrows underground, and pupates. The searching behaviour is known as "wandering". The instinct of wandering can be visually confirmed by spotting the heart (aorta) which is a long, pulsating vein running along the length of the caterpillar's dorsal side. The heart appears just as the caterpillar is reaching the end of the final instar. M. sexta has five larval instars which are separated by ecdysis (molting), but may add larval instars when nutrient conditions are poor. The pupal stage lasts approximately 18 days under laboratory conditions (17 hours light, 7 hours dark, 27 °C). When reared on a short-day photoperiod (12 hours light, 12 hours dark), pupae enter a state of diapause that can last several months. During the pupal stage, structures of the adult moth form within the pupal case which is shed during eclosion (adult emergence). Adult M. sexta are known as Carolina sphinx moths. M. sexta moths are nectarivorous and feed on flowers, demonstrating a remarkable ability to hover.

Habitat:

Tobacco fields, vegetable gardens, and a wide variety of habitats.

Notes:

Although the larvae are considered pests, the moths are important pollinators of deep-throated, night-blooming flowers, so the good and bad equal themselves.