The five-spotted hawkmoth (Manduca quinquemaculata) is a brown and gray hawk moth of the Sphingidae family. The caterpillar, often referred to as the tomato hornworm, can be a major pest in gardens. Tomato hornworms are closely related to (and sometimes confused with) the tobacco hornworm (Manduca sexta). This confusion arises because caterpillars of both species feed on the foliage of various plants from the family Solanaceae, so either species can be found on tobacco or tomato leaves, and the plant on which the caterpillar is found does not indicate its species. 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. 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. The moths can be distinguished by the number of spots on their abdomens, with M. quinquemaculata having, as its name suggests, five.
Tomato hornworms are known to eat various plants from the family Solanaceae, commonly feeding on tomato, eggplant, pepper, tobacco, moonflowers and potato. Accordingly, they are often found on defoliated tomato plants, the caterpillar clinging to the underside of a branch near the trunk. They are difficult to spot due to their green coloration. Tomato hornworms fluoresce differently from tomato leaves. Using an ultraviolet light source of 375 nm and viewed behind a blue-blocking filter (yellow or amber filter), a tomato hornworm fluoresces in bright green while a tomato leaf appears deep red/amber. This sharp color contrast helps gardeners locate tomato hornworms at night. They can be reduced by planting marigold flowers around these plants.
Hornworm eggs are spherical to oval in shape, measure about 1.5 mm (0.059 in) in diameter, and vary in color from light green to white. Eggs are deposited principally on the lower surface of foliage, but also on the upper surface. Duration of the egg stage is two to eight days, but averages five days.
The tomato hornworm is a green caterpillar, with eight light-green v-shaped markings which extend from the dorsal line to its sides. At the rear end, the caterpillar has a black, bumpy horn, from which the name for the "hornworm" is derived. Nine spiracles (colored black and yellow) appear on each side of the body and are used for respiration.
During the summer months, moths emerge from pupae in about two weeks. Moths emerge from the soil, mate, and then begin to deposit the eggs of the next generation on tomato plants. By early fall, the pupae remain in the soil all winter and emerge as moths the following spring. They have been found on other green leaf plants such as moon flowers.
- "CATE Creating a Taxonomic eScience - Sphingidae". Cate-sphingidae.org. Retrieved 2011-11-01.
- Villanueva, Raul (June 1998). "Tobacco Hornworm". Retrieved 2006-10-21.
- "Marigolds". Davis Wiki. 1999-02-22. Retrieved 2011-11-01.