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How to identify it
- The caterpillar is usually greenish, sometimes reddish, with seven pairs of slanting stripes along the sides, a pink or yellow band on each side of the head running from the eyes to the crown, and a pinkish tail horn.[1]
- The plate on top of the last segment is rounded, and that plate and the hindmost prolegs carry conspicuous black spots.[1]
- Like almost all hornworms, it has a horn on top of the eighth abdominal segment, and its large droppings often give it away in a tree or garden.[1]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Great ash sphinx | Its caterpillar feeds on the same ash, lilac and privet and looks similar, but it has white granular spotting, especially on the thorax and below the breathing pores, its side stripes reach forward to above the proleg of the segment in front, and its anal plate is flat and lacks the waved sphinx's black spots.[1] |
| Catalpa sphinx | A close relative in the same genus, but its caterpillars are marked in yellow and black, feed in groups, and specialize on catalpa. The two species are attacked by the same specialist parasitoid.[1][2] |
Where it lives
The USDA Forest Service includes it among the caterpillars of eastern forests, with two generations a year in the South and one in the North.[1]
Biology and life cycle
Ash is the preferred food plant, but the caterpillars also eat lilac, privet, hawthorn, oak and other trees. Caterpillars can be found from April through October.[1]
Its usual hosts belong to the olive family, plants that produce defensive compounds called seco-iridoid glycosides. In lab tests the waved sphinx could not store catalpol, a defensive compound the catalpa sphinx sequesters, and adding catalpol to its diet weakened its immune response.[2]
Like other hornworms, full-grown caterpillars are often found wandering over the ground in search of a place to pupate.[1]
Damage and signs
- The caterpillars eat the leaves of ash, lilac, privet and other trees and shrubs. The USDA Forest Service guide does not describe it as a pest.[1]
Health risk
Hornworms may thrash violently and regurgitate when handled, but neither source mentions any bite, sting or other risk to people.[1][2]
Control
Prevention
Neither source recommends any control for the waved sphinx.[1][2]
Common questions
- What is the big green caterpillar with slanting stripes on my lilac or ash?
- It may be a waved sphinx or a great ash sphinx, which share those food plants. The waved sphinx lacks white granular spots and has black spots on its rounded rear plate and hindmost prolegs.[1]
- Is the waved sphinx related to the catalpa worm?
- Yes. Both are in the genus Ceratomia and share a specialist parasitoid, but the waved sphinx feeds mainly on ash and its relatives, while the catalpa sphinx specializes on catalpa.[2][1]
Sources
- USDA Forest Service, Forest Health Technology Enterprise Team, “Caterpillars of Eastern Forests, FHTET-96-34 (D. L. Wagner, V. Giles, R. C. Reardon and M. L. McManus, November 1997; scanned copy).” archive.org/details/caterpillarsofea001997 (accessed 2026-11-09)
- Journal of Chemical Ecology (via NCBI PubMed), “Incompatibility between plant-derived defensive chemistry and immune response of two sphingid herbivores (E. C. Lampert and M. D. Bowers; Journal of Chemical Ecology 41(1): 85-92, 2015; abstract).” pubmed.ncbi.nlm.nih.gov/25516226/ (accessed 2026-11-09)
- iNaturalist, “Ceratomia undulosa taxon page (order and family).” www.inaturalist.org/taxa/82153 (accessed 2026-11-09)