NC State Extension Publications

Description and Biology

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The rustic sphinx, Manduca rustica, is a moth in the same genus as the tobaccofly (tobacco hornworm) and the tomato hornworm. These moths are moderately large (wing span from 31/2 to almost 6 inches) with heavy bodies and are usually nocturnal, feeding late at night. Rustic sphinx moths are mottled and zig-zagged with black and white or very dark brown and white markings except for three pairs of yellow spots on the abdomen that are usually covered by the wings. When at rest, the wings are held slightly away from the body forming an isoceles triangle. Each wing has a large, dark area on the outer margin with a tiny white dot in the middle. Females lay one to five eggs on the undersides of host leaves. A large female can lay up to 2,000 eggs! Tiny caterpillars hatch about four days later. The rustic sphinx caterpillar is bright green with white to yellow diagonal stripes bordered with darker green to purple-black on the top of each stripe. The horn at the end is harmless and has tiny bumps that help distinguish the rustic sphinx from other hornworms. The head and upper thorax also have tiny bumps. The color and pattern is constant as the hornworm molts and grows. After three weeks, the upper surface becomes light reddish-brown just before the caterpillar crawls down to pupate in the soil. Rustic sphinx caterpillars are often found in the "sphinx position" (When disturbed, they hold onto the plant and raise their heads and thoraces to more or less resemble the ancient Egyptian Great Sphinx). Mature caterpillars tunnel into the soil, make a cavity, and then pupate within. The pupae are tapered on each end and very dark brown. The mothparts form a loop on the lower surface. About three weeks later, new moths emerge from the pupae and dig out to continue the wheel of existence. The last generation of rustic sphinx caterpillars form overwintering pupae. We have at least two generations per year here in North Carolina although several broods occur from May-October further south.

Rustic sphinx caterpillar

Rustic sphinx caterpillars can grow up to three inches long.

Rustic sphinx pupa

Rustic sphinx pupae occur in soil.

Rustic sphinx moth

Rustic sphinx moths usually fly way after dusk.

Host Plants

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Rustic sphinx caterpillars have been found feeding on American beautyberry, ash, basil, butterfly bush, crape myrtle, cross vine, desert willow, forked bluecurls, fringe tree, gardenia, heliotrope, jasmine, lantana, ligustrum, lilac, olive, sesame, and sunflower. The moths visit just about anything in bloom at night including flowers with deep corollas such as petunia.

Residential Recommendations

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Rustic sphinx caterpillars are plagued by a tiny wasp, Cotesia congregata, the larvae of which develop inside the hornworm before chewing out and spinning tiny cocoons that are fastened to the worm. Other predators and parasites also infest rustic sphinx eggs, caterpillars, and pupae. Because this is a sporadic pest, it would be unwise to apply an insecticide prophylactically. Large numbers devouring a plant can be hand picked and trampled underfoot. Any insecticide labeled for landscape use should give more than adequate control.

Cotesia congregata and other parasites

Cotesia congregata and other parasites and predators can greatly limit rustic sphinx populations.

Other Resources

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology & Plant Pathology

Publication date: July 18, 2019
Revised: Oct. 12, 2019

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