Caterpillar Varieties: How to Identify Common Caterpillars

• Relationship to adults: complete metamorphosis passes through egg, larva (the caterpillar), pupa, and adult; the larva molts several times before pupating, forming either a chrysalis or a cocoon.
• Distinguishing from beetle larvae (grubs): beetle larvae, such as leaf beetle larvae, have no prolegs but do have true legs.
• Distinguishing from fly larvae (maggots): fly larvae lack true legs entirely and have only fleshy protuberances on the abdomen or on both the abdomen and thorax.
• Distinguishing from sawfly larvae (not one of this set's groups, but similar in appearance to caterpillars): sawfly larvae have prolegs on six or more abdominal segments, more than the five or fewer found on caterpillars.

People most often mix caterpillars up with:

• Grubs
• Maggots

Open the other page and compare its list against the marks above; the differences are usually in the antennae, wings or the way the body is divided.

Not all caterpillars sting, but some species (flannel moth/puss moth caterpillars) have venomous hairs or spines that cause intense pain and even systemic symptoms on contact; other species (such as the hickory tussock moth caterpillar) cause only localized rash and itching rather than a true sting. Seek medical care promptly for severe symptoms or any allergic reaction.

Feeding on foliage can kill or stunt the growth of young plants; caterpillars are a common pest of garden and landscape plants.

Mostly found on host plants or in the soil near them; garden flowers are especially susceptible to damage.

Get as close as your camera will focus, from directly above, in daylight or a bright lamp. Include the whole body with the legs and antennae in frame; a second shot from the side shows wings and body segments. Put a coin or ruler next to it for scale. For a bite or a bug found on skin or bedding, photograph the bug itself, not the mark. The app names the likely group; use the list above to confirm.

You identify a caterpillar from five things: its hairs or spines, its colours, its markings, the plant it is eating and the time of year. That is the checklist the UK's Wildlife Trusts use, and it matches how the field guide *Lepidoptera of the Pacific Northwest* (published online by Oregon State University's H.J. Andrews Experimental Forest) describes each of its 239 photographed species: body colour, the position of lines and stripes, head colour, food plants and season.

• Hairs: smooth, sparsely hairy, densely furry, tufted, or spiny
• Colour and pattern: bands across the body, stripes along it, spots, eyespots
• Special features: a horn at the tail end (hornworms and other hawk-moth caterpillars), eyespots near the head (elephant hawk-moth)
• Food plant: many caterpillars eat only one plant family, so the plant narrows the list sharply
• Leg count: the Wildlife Trusts note that sawfly larvae, which look like caterpillars, usually have six or more pairs of stumpy prolegs, while caterpillars have five or fewer

Colours change as caterpillars grow, and young ones can look nothing like the mature larva, so a single colour chart is a starting point, not a verdict.

These are caterpillars that North American extension services and the UK Wildlife Trusts single out. Where a species is British rather than North American, that is noted.

Green

• Tomato hornworm: up to 4 inches; young ones are yellow to white with no markings, larger ones develop eight white V-shaped marks on each side and have a black horn on the last segment (University of Minnesota Extension). Found on tomatoes.
• Elephant hawk-moth (UK): up to 8.5 cm, green or brown, several eyespots at the front and a spiky tail (Wildlife Trusts).
• Privet hawk-moth (UK): up to 8.5 cm, green with purple and white stripes and a black and yellow horn (Wildlife Trusts).

Striped yellow, black and white

• Monarch: bands of yellow, black and white, up to 2 inches, feeding only on milkweed (National Wildlife Federation).
• Cinnabar (UK): black and yellow stripes, on ragwort (Wildlife Trusts).

Black, brown and orange, hairy

• Banded woolly bear: black at both ends with a rusty-red middle, stiff hairs (NC State Extension). Often the answer to "black and brown caterpillar" in the US.
• Garden tiger (UK, also called woolly bear): up to 6 cm, mostly black and ginger with longer white hairs (Wildlife Trusts).

Boldly patterned, in a silk tent

• Eastern tent caterpillar: black, orange, white and blue, with a white stripe down the back when mature; tents in branch forks in early spring (University of Maryland Extension).
• Forest tent caterpillar: similar, but with keyhole-shaped white spots instead of a stripe, and no true tent (UMD).
• Fall webworm: active later in summer and into fall, with webs at the ends of branches rather than in forks (UMD).

Black and spiny

• Peacock butterfly (UK): up to 4.5 cm, black with black spines and small white dots, in communal webs on nettles (Wildlife Trusts).

On parsley, dill and carrots

• Black swallowtail: up to 1 1/2 inches, on parsley, carrots, dill, fennel, celery and Queen Anne's lace, July to September in Minnesota; UMN says its feeding is rarely enough to seriously harm plants.

Some caterpillars have hairs or spines that cause pain or skin irritation, so the safe habit is not to handle any hairy or spiny caterpillar with bare hands.

• Southern flannel moth caterpillar ("puss caterpillar"): teardrop-shaped, with long silky hairs that make it look like a tuft of cotton or fur, yellow or grey to reddish-brown, 1 to 1 1/2 inches when mature (Texas A&M).
• Io moth, saddleback and buck moth caterpillars: Texas A&M lists these as other common stinging caterpillars in Texas.
• Brown-tail and yellow-tail (UK): the Wildlife Trusts note their hairs cause skin irritation.

Texas A&M's first-aid notes are an ice pack on the site and oral antihistamines for itching and burning, and for stout-spined species such as io and saddleback caterpillars, pressing cellophane tape on the site and peeling it off. Get medical care for severe pain, a spreading reaction or any sign of an allergic reaction; in the United States, Poison Help on 1-800-222-1222 can advise.

Photograph the caterpillar from above and from the side, on the plant it was eating, with something for scale. Then use any of these:

• An identification app: photograph it and the app identifies it, then compare with the colour list above.
• Google Lens: compares your picture with other images and ranks the most similar, usually offering several possible matches.
• Seek by iNaturalist: free and needs no account.
• CaterpillarIdentification.org: has an "Identify this Caterpillar" tool and a state-by-state index covering moth, butterfly and skipper caterpillars of North America.
• A field guide: *Lepidoptera of the Pacific Northwest* pairs caterpillar and adult photos for 239 species, with food plants and season.

If the caterpillar is a garden pest, check grubs and maggots too; both get mistaken for caterpillars.

Research and drafting for this page used AI assistance. Every figure, date and quotation was then checked line by line against the sources listed at the bottom of the page, each of which was opened while writing. Nothing here is a diagnosis. If a bite, sting or contact with an insect is followed by trouble breathing, swelling of the face or throat, spreading redness, fever or any symptom that worries you, get medical care; in the United States Poison Help (1-800-222-1222) is free and open 24 hours a day.