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How to identify it
- The caterpillar is green, up to 30 to 35 mm (about 1.25 inches), with bright white stripes down the middle and upper sides of the back.[1][2][3]
- Its most striking feature is the stripe along each side at the level of the breathing holes: red (or red-black) above and white and yellow below, broken into separate oval segments.[1][2][3]
- Below that runs a row of oblong yellow spots above the legs. The head is pale or light bluish green and unmarked, and the thoracic legs are reddish brown.[1][2][3]
- Seen up close, the skin has a dimpled texture.[2]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Comstock's sallow (Feralia comstocki) | Very similar, but its white, yellow and red side stripe is continuous rather than broken into segments, its yellow spots below are less elongate, and its head has dark marks.[2][3] |
| Major sallow (Feralia major) | Another similarly patterned Feralia, found mainly on pine in the Northeast.[1][2] |
Where it lives
It lives in conifer forests in Canada and the northeastern United States, where two other Feralia species with similar patterns occur over much of its range.[1][2][3]
Biology and life cycle
Hosts are conifers: fir, spruce, hemlock and other conifers in the East; Natural Resources Canada lists balsam, grand, subalpine and amabilis fir, several spruces, western and mountain hemlock, Douglas-fir, tamarack and western larch.[1][2][3]
There is one generation a year. The pupa overwinters in the soil or debris, the moths fly in May and June, and caterpillars are present from May to July in the Northeast and from June to August in Canada, pupating by August.[1][2][3]
Damage and signs
- The caterpillars eat needles, feeding alone and moving about freely on the foliage. Natural Resources Canada describes the species as a common but innocuous defoliator.[3]
Health risk
For all its bright colors, none of the forest sources reports any risk to people from this caterpillar.[1][2][3]
Control
Prevention
No control is recommended: Natural Resources Canada considers it innocuous, and the USDA Forest Service guides give no control advice.[3][1][2]
Common questions
- What is the green caterpillar with a red and white stripe on my fir tree?
- A good match is the jocose sallow (redlined conifer caterpillar): green, with white stripes on the back and a red, white and yellow stripe along each side broken into oval segments. It feeds on fir, spruce, hemlock and other conifers.[1][2][3]
- Should I spray for it?
- No control is called for. Natural Resources Canada describes it as a common but innocuous defoliator that feeds alone.[3]
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)
- USDA Forest Service, Forest Health Technology Enterprise Team, “Red-marked caterpillar (Feralia jocosa), from Caterpillars on the Foliage of Conifers in the Northeastern United States, FHTET-2004-01 (C. T. Maier, C. R. Lemmon, J. M. Fengler, D. F. Schweitzer and R. C. Reardon, 2004), Bugwood wiki archive.” wiki.bugwood.org/Archive:Caterpillars/Feralia_jocosa (accessed 2026-11-09)
- Natural Resources Canada, Canadian Forest Service, “Redlined conifer caterpillar, Trees, insects and diseases of Canada's forests.” tidcf.nrcan.gc.ca/en/insects/factsheet/10041 (accessed 2026-11-09)
- iNaturalist, “Feralia jocosa taxon page (order and family).” www.inaturalist.org/taxa/220088 (accessed 2026-11-09)