**Caterpillar Identification Chart — Colour, Hair & Host**

> Free caterpillar identification key: filter 34 North American caterpillars by colour, hairiness, size and host plant. The ones that sting are flagged.

Source: https://orvik.app/tools/caterpillar-identifier/ · updated: 2026-09-03

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Insects & spiders

# What caterpillar is this?

The plant it was sitting on is the strongest clue you have. Most caterpillars eat a short list of hosts, so **"green, on a tomato plant"** is a far better query than "green caterpillar". Filter by host first, then by whether it is smooth, furry or spiny — and check the sting column before you pick it up.

Entries **34** Filters **5** Updated **2026-09-03** Cost **Free, no account**

**Some of these sting.** Puss, saddleback, io, buck moth and spiny oak slug caterpillars carry venomous spines that break off in skin and cause burning pain, welts and occasionally a systemic reaction. **Never handle a caterpillar with spines, tufts or dense fur.** If you are stung, strip the spines off with tape before washing, then ice; get medical help for chest pain, difficulty breathing, or if the person has a history of severe reactions.

Narrow it down

Clear all

Search caterpillars by name

Surface

The single best filter after host plant.

Smooth and naked Hairy or furry Distinct tufts or pencils of hair Branched spines or bristles Horn on the rear end Coloured knobs or bumps

Main colour

Green Brown or grey Black Yellow or orange White or pale Boldly striped or banded

Full-grown length

Under 2.5 cm / 1 in 2.5–5 cm / 1–2 in 5–8 cm / 2–3 in Over 8 cm / 3 in

What it was on

If you know the plant, start here.

Milkweed Vegetable garden Parsley, dill or carrot tops Broadleaf tree or shrub Oak Cherry, apple or crabapple Lawn or field grass Crossing the ground

Does it sting?

Safe to handle Can irritate skin Stings — do not touch

Showing all 34 caterpillars

1. ### Monarch Danaus plexippus Bold bands of yellow, white and black around a smooth body, with two pairs of soft black filaments — one behind the head, one near the tail. Only ever on milkweed. Size Up to 4.5 cm Where The whole of North America wherever milkweed grows. Confused with Queen caterpillar, which has three pairs of filaments instead of two. Count the filaments. In the record 799,895 georeferenced records · half of them Jul–Sep · most distinctive in January · mostly from the United States [check on GBIF](https://www.gbif.org/species/5133088)

2. [Common caterpillar types](https://orvik.app/insects/types-of-caterpillars/)

3. ### Black swallowtail Papilio polyxenes Green with black bands and a row of yellow-orange dots on each band, found on parsley, dill, fennel or carrot tops. Poke it gently and an orange forked organ pops out of the head, smelling sour. Size 4–5 cm Where Eastern and central North America. Confused with Monarch. Both are banded, but the swallowtail is green between the bands and never on milkweed. In the record 118,300 georeferenced records · half of them Jun–Aug · most distinctive in February · mostly from the United States [check on GBIF](https://www.gbif.org/species/1937816)

4. ### Tomato hornworm Manduca quinquemaculata Enormous, plump, bright green, with eight white V-shaped marks pointing forward along each side and a black or dark-blue horn on the rear. Size 7–10 cm Where Vegetable gardens across North America. Confused with Tobacco hornworm, which has seven straight white diagonal stripes and a red horn. Count the marks and check the horn colour. In the record 5,963 georeferenced records · half of them Jun–Aug · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/1864008)

5. ### Tobacco hornworm Manduca sexta Seven straight white diagonal stripes along each side and a curved red horn. This is the hornworm most often found on tomatoes despite the name. Size 7–10 cm Where The US South and, in summer, most of the country. Confused with Tomato hornworm — V-marks and a dark horn. In the record 21,557 georeferenced records · half of them Jul–Aug · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/1863978)

6. ### Woolly bear Pyrrharctia isabella Dense stiff bristles, black at both ends with a rust-brown band in the middle, hurrying across a road or path in September and October looking for somewhere to overwinter. Size 4–5 cm Where Across North America, conspicuous in autumn. Confused with The folk belief that the band width forecasts the winter is not supported — band width tracks the caterpillar's age and how wet the previous season was. In the record 73,490 georeferenced records · half of them Aug–Oct · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/1807881)

7. ### Yellow woolly bear Spilosoma virginica A uniformly shaggy caterpillar in pale yellow, cream or occasionally rust, with no black ends. The long soft hairs can irritate sensitive skin, unlike the true woolly bear. Size 3–4.5 cm Where Across North America. In the record 39,530 georeferenced records · half of them Jun–Aug · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/1811948)

8. ### Eastern tent caterpillar Malacosoma americanum A continuous white stripe down the centre of the back, blue and orange dashes along the sides, and a dense silk tent built in the fork of a wild cherry or apple branch in April and May. Size 4–5 cm Where Eastern North America, appearing in spring. Confused with Fall webworm. Tent caterpillars build in branch forks in spring and feed outside the tent; webworms wrap the leaves at branch tips in late summer and feed inside. In the record 46,809 georeferenced records · half of them Apr–May · most distinctive in April · mostly from the United States [check on GBIF](https://www.gbif.org/species/5715280)

9. ### Forest tent caterpillar Malacosoma disstria A row of white keyhole or footprint shapes down the back instead of a continuous line, and it builds no tent — it spins a silk mat on the trunk and rests there in a mass. Size 4–5 cm Where North America, in periodic outbreak years. In the record 29,306 georeferenced records · half of them Apr–Jun · most distinctive in April · mostly from the United States [check on GBIF](https://www.gbif.org/species/5101763)

10. ### Fall webworm Hyphantria cunea Pale hairy caterpillars living inside a loose grey web that encloses the leaves at the very tip of a branch, expanding through August and September. Ugly, harmless to the tree. Size 2.5–3.5 cm Where North America, and introduced across Europe and Asia. In the record 50,172 georeferenced records · half of them Jun–Aug · most distinctive in November · mostly from the United States [check on GBIF](https://www.gbif.org/species/1817797)

11. ### Spongy moth Lymantria dispar Five pairs of blue dots followed by six pairs of red dots down the back — a colour sequence nothing else has — with long straggling hairs. Formerly called the gypsy moth. Size 4–6 cm Where The northeastern US, the Great Lakes and eastern Canada. Risk The hairs cause an itchy rash in a substantial minority of people during outbreak years. In the record 146,176 georeferenced records · half of them Jun–Jul · most distinctive in June · mostly from the Netherlands [check on GBIF](https://www.gbif.org/species/1820406)

12. ### White-marked tussock moth Handle with care Orgyia leucostigma A bright red head, four short cream toothbrush tufts on the back, and two long black hair pencils pointing forward with one pointing back. Unmistakable once seen. Size 2.5–3.5 cm Where Eastern North America. Risk The hairs cause contact dermatitis and are shed into the cocoon, so old cocoons on siding also itch. In the record 24,554 georeferenced records · half of them Jun–Aug · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/5925317)

13. ### Hickory tussock moth Handle with care Lophocampa caryae White and fluffy with a row of black tufts down the back and four long black pencils at each end, found on hickory, walnut and ash — and very often crossing a sidewalk in August. Size 3.5–4.5 cm Where Eastern North America, conspicuous in late summer. Risk A common cause of childhood rashes because it is white, fluffy and irresistible. The hairs sting on contact. In the record 41,768 georeferenced records · half of them Aug–Sep · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/1817732)

14. ### Milkweed tussock moth Euchaetes egle Clusters of caterpillars covered in dense tufts of black, orange and white hair, stripping a milkweed leaf together late in the season after the monarchs have gone. Size 3 cm Where Eastern and central North America. In the record 31,712 georeferenced records · half of them Aug–Aug · most distinctive in August · mostly from the United States [check on GBIF](https://www.gbif.org/species/5116353)

15. ### Puss caterpillar Can injure you Megalopyge opercularis Looks like a small toupee or a tuft of cotton wool, tan to grey, with a pointed tail of longer hair. The venomous spines are hidden entirely under the soft outer fur. Size 2–3.5 cm Where Texas east to Florida and north to Maryland; outbreak years bring hospital visits. Risk The most painful caterpillar sting in the United States: immediate throbbing pain radiating up the limb, a gridded red rash, sometimes nausea and shock. Tape off the spines, ice, and seek care for systemic symptoms. In the record 9,349 georeferenced records · half of them Apr–Jul · most distinctive in November · mostly from the United States [check on GBIF](https://www.gbif.org/species/1751572)

16. ### Saddleback caterpillar Can injure you Acharia stimulea A brown slug-like body with a bright green blanket across the middle carrying a purple-brown oval "saddle", and four stout horned spine clusters at the corners. Size 2–2.5 cm Where Eastern United States. Risk Severe burning sting with swelling that can last a day. Common on garden shrubs and blueberry, so it gets grabbed while picking. In the record 6,702 georeferenced records · half of them Jul–Aug · most distinctive in September · mostly from the United States [check on GBIF](https://www.gbif.org/species/9776414)

17. ### Io moth caterpillar Can injure you Automeris io Pale green with a red-and-white stripe along each side and dense clusters of branched, bright green venomous spines over the whole body. Size 5–6 cm Where Eastern and central North America. Risk The spines break off and inject venom; expect intense stinging for an hour and a welt for days. In the record 24,812 georeferenced records · half of them May–Jul · most distinctive in December · mostly from the United States [check on GBIF](https://www.gbif.org/species/1866085)

18. ### Buck moth caterpillar Can injure you Hemileuca maia Dark purple-black speckled with white dots and armed with rosettes of branched, hollow, cream-tipped spines. Feeds in groups on oak, often dropping on people below. Size 5–6 cm Where Oak woodland in the eastern US; a public-health nuisance in New Orleans. Risk Stings on contact and the spines remain active in the shed skins and on the ground beneath infested oaks. In the record 1,061 georeferenced records · half of them Sep–Oct · most distinctive in October · mostly from the United States [check on GBIF](https://www.gbif.org/species/1865313)

19. ### Spiny oak slug Can injure you Euclea delphinii Flat, oval and slug-shaped with no visible head, in green or yellow, edged with paired spiny horns and usually carrying four dark spots on the back. Size 1.5–2 cm Where Eastern United States. Risk A mild-looking caterpillar with a genuine sting. Very often found on the underside of an oak leaf you are turning over. In the record 8,443 georeferenced records · half of them Jun–Jul · most distinctive in June · mostly from the United States [check on GBIF](https://www.gbif.org/species/5105365)

20. ### Luna moth caterpillar Actias luna Fat, bright translucent green with a faint yellow line along each side and small orange knobs down the back, each with a short bristle. It clicks its mandibles if disturbed. Size 6–9 cm Where Eastern North America, on walnut, hickory, sweetgum and birch. In the record 47,535 georeferenced records · half of them May–Jul · most distinctive in March · mostly from the United States [check on GBIF](https://www.gbif.org/species/1865668)

21. ### Cecropia moth caterpillar Hyalophora cecropia The largest caterpillar in North America: a thumb-thick blue-green body studded with blue, yellow and red knobs carrying black spines. Alarming and completely harmless. Size 10 cm Where Eastern North America. In the record 13,844 georeferenced records · half of them Apr–Jun · most distinctive in February · mostly from the United States [check on GBIF](https://www.gbif.org/species/1865839)

22. ### Polyphemus moth caterpillar Antheraea polyphemus Bright apple-green with a diagonal yellow line running back from each pair of legs and small red-and-silver knobs. Body is strongly ridged into fat segments. Size 7–9 cm Where Across North America. In the record 53,407 georeferenced records · half of them May–Jul · most distinctive in February · mostly from the United States [check on GBIF](https://www.gbif.org/species/1866570)

23. ### Mourning cloak caterpillar Nymphalis antiopa Velvety black speckled with white, a row of eight red-orange spots down the back and branched black spines. Feeds in a dense group that strips a whole branch at once. Size 4–5 cm Where North America and Europe, on willow, elm and hackberry. Confused with Spines that look dangerous but are not — this species does not sting. In the record 247,233 georeferenced records · half of them Apr–Jun · most distinctive in April · mostly from Finland [check on GBIF](https://www.gbif.org/species/5130682)

24. ### Great spangled fritillary caterpillar Speyeria cybele Velvety black with orange-based branched spines, feeding only on violets and only at night — which is why it is usually found on the ground rather than on a plant. Size 4–5 cm Where Meadows and woodland edge across North America. In the record 62,911 georeferenced records · half of them Jun–Jul · most distinctive in June · mostly from the United States [check on GBIF](https://www.gbif.org/species/1905172)

25. ### Cabbage looper Trichoplusia ni Smooth pale green with thin white side stripes, tapering towards the head, and it moves by arching its back into a loop because it lacks the middle pairs of prolegs. Size 3–4 cm Where Vegetable gardens worldwide. Confused with Imported cabbageworm, which crawls normally and is velvety rather than smooth. If it loops, it is a looper. In the record 8,810 georeferenced records · half of them Jun–Aug · most distinctive in November · mostly from the United States [check on GBIF](https://www.gbif.org/species/1786360)

26. ### Imported cabbageworm Pieris rapae Velvety, uniformly green with a faint yellow line down the back, matching the leaf so closely it is usually found by its dark green droppings rather than by sight. Size 2.5–3 cm Where Anywhere brassicas are grown, worldwide. In the record 3,687,718 georeferenced records · half of them Jul–Aug · most distinctive in July · mostly from the United Kingdom [check on GBIF](https://www.gbif.org/species/1920496)

27. ### Fall armyworm Spodoptera frugiperda Brown to green with stripes and four black dots in a square on the second-to-last segment, plus a pale inverted Y on the front of the head capsule. Arrives in a lawn as a moving front. Size 3–4 cm Where The Americas, now established across Africa and Asia. Confused with Other cutworms. The inverted Y on the head is the reliable character. In the record 13,635 georeferenced records · half of them Jul–Sep · most distinctive in November · mostly from the United States [check on GBIF](https://www.gbif.org/species/5109855)

28. ### Cutworm Agrotis and Noctua species Dull, greasy-looking and unmarked, found curled into a tight C just under the soil surface beside a seedling that was cut off at ground level overnight. Size 3–5 cm Where Worldwide. In the record 1,987,359 georeferenced records · half of them Jun–Jul · most distinctive in June · mostly from the United Kingdom [check on GBIF](https://www.gbif.org/species/8407958)

29. ### Bagworm Thyridopteryx ephemeraeformis You rarely see the caterpillar at all — only a spindle-shaped bag of silk covered in fragments of the host's own needles or leaves, hanging from a twig and moving slowly. Size Bag 3–5 cm Where Eastern and central United States, mostly on conifers. Confused with A cone or a piece of dead foliage, which is exactly the point. In the record 10,695 georeferenced records · half of them May–Sep · most distinctive in February · mostly from the United States [check on GBIF](https://www.gbif.org/species/1853312)

30. ### Inchworm or cankerworm Geometridae Thin, twig-like, with legs at the front and rear only, so it moves by looping. At rest it holds itself out rigidly from a twig at an angle, imitating a shoot. Size 2–3 cm Where Everywhere. In the record 24,385,819 georeferenced records · half of them May–Jul · most distinctive in February · mostly from the United Kingdom [check on GBIF](https://www.gbif.org/species/6950)

31. ### Spicebush swallowtail Papilio troilus Smooth green with two huge false eyespots on the swollen thorax that make it look like a small snake, resting inside a leaf it has folded and tied with silk. Size 4–5 cm Where Eastern United States, on spicebush and sassafras. In the record 50,421 georeferenced records · half of them Jul–Aug · most distinctive in March · mostly from the United States [check on GBIF](https://www.gbif.org/species/1938104)

32. ### Eastern tiger swallowtail Papilio glaucus Plump smooth green with a swollen front end carrying two yellow-and-black eyespots and a thin yellow-and-black band behind them. Young larvae are brown and white, mimicking bird droppings. Size 5 cm Where Eastern North America, on tulip tree, cherry and ash. In the record 127,549 georeferenced records · half of them Jul–Aug · most distinctive in March · mostly from the United States [check on GBIF](https://www.gbif.org/species/1938016)

33. ### Catalpa sphinx Ceratomia catalpae Black and yellow with a shiny black horn, feeding in large groups that can strip a catalpa completely. Found on catalpa and nothing else, which makes it trivially identifiable. Size 5–7 cm Where The eastern and southern United States, only on catalpa trees. In the record 6,932 georeferenced records · half of them Jul–Aug · most distinctive in September · mostly from the United States [check on GBIF](https://www.gbif.org/species/1861892)

34. ### Hummingbird moth caterpillar Hemaris thysbe Pale green with a yellowish stripe on each side and a short blue-green horn, on honeysuckle. It becomes the clearwing moth people mistake for a hummingbird. Size 4–5 cm Where Eastern North America, on honeysuckle, viburnum and snowberry. In the record 21,951 georeferenced records · half of them Jun–Jul · most distinctive in July · mostly from the United States [check on GBIF](https://www.gbif.org/species/1861851)

35. ### Viceroy caterpillar Limenitis archippus Lumpy, saddle-shaped and mottled olive-brown and cream so it reads convincingly as a bird dropping, with two bristly knobs behind the head. Size 3 cm Where North America, on willow, poplar and aspen. In the record 54,362 georeferenced records · half of them Jul–Aug · most distinctive in June · mostly from the United States [check on GBIF](https://www.gbif.org/species/5132398)

Nothing in this key matches every filter at once. That usually means one observation is
off — a colour read in shade, or a size guessed rather than measured. Clear the filter you
are least sure about and look again.

## Start with the plant, not the picture

Caterpillars are picky in a way that adult butterflies are not. Most species feed on one plant family and many on a single genus, which means the host is doing far more identification work than colour ever will. A green caterpillar could be any of forty things; a green caterpillar on a tomato plant is one of two.

The strongest host associations in North America are worth memorising outright:

*Host plants that effectively name the caterpillar. Associations follow standard regional references and state extension guides.*

| Found on | Almost certainly | Also possible |
| --- | --- | --- |
| Milkweed | Monarch | Queen, milkweed tussock moth |
| Parsley, dill, fennel, carrot tops | Black swallowtail | Anise swallowtail in the west |
| Tomato, pepper, potato | Tobacco or tomato hornworm | Hornworm parasitised by braconid wasps |
| Cabbage, kale, broccoli | Imported cabbageworm or cabbage looper | Diamondback moth, cross-striped cabbageworm |
| Catalpa | Catalpa sphinx | Nothing else, in practice |
| Spicebush or sassafras | Spicebush swallowtail | Promethea moth |
| Wild cherry, in a spring tent | Eastern tent caterpillar | Forest tent caterpillar, on the trunk |
| Violets, at night | Fritillary | Nothing else feeds only on violets |

If the caterpillar is crossing a path or a road it has almost certainly left its host to pupate, and the host filter will not help. That is the one case where you fall back on texture and colour — and it is also why woolly bears, which do exactly this every autumn, are the most photographed caterpillar in North America.

## The stinging ones, and how to recognise them before you touch

Roughly two dozen North American caterpillars can sting, and five of them account for nearly every emergency-room visit. The mechanism is not a bite: hollow spines connected to venom glands break off in the skin and keep releasing venom, which is why the pain builds over the first ten minutes rather than fading.

The reliable warning signs, in order of usefulness:

- **Branched or clustered spines** — io, saddleback, buck moth, spiny oak slug. Simple single bristles are usually harmless; spines that themselves branch into more spines are the dangerous pattern.
- **A slug-like body with no visible head or legs.** The slug caterpillars (family Limacodidae) include most of the worst stingers, and they all look like a small flattened blob glued to the underside of a leaf.
- **Dense fur that looks soft and inviting.** The puss caterpillar hides its venomous spines entirely under a coat of long hair that looks like a scrap of felt. Anything that makes you want to stroke it should not be stroked.
- **Tufts, pencils and toothbrush ridges.** Tussock moths cause dermatitis rather than a true sting, but the reaction can be substantial and the hairs persist on cocoons and shed skins for months.

**If you are stung:** lift the embedded spines out with adhesive tape applied and pulled off repeatedly before you touch the area with anything else — rubbing pushes them deeper. Then wash with soap and water, apply ice, and take an oral antihistamine. Seek medical care for chest pain, difficulty breathing, extensive swelling, stings around the eye, or in a child with a known allergy history.

The reverse rule is worth stating too: a great many alarming-looking caterpillars are entirely harmless. Cecropia, luna, mourning cloak and fritillary caterpillars all bristle with spines and none of them sting.

## Why the same species can look like two different animals

Three sources of variation defeat photo-matching more often than anything else, and knowing about them prevents most misidentifications.

**Instars.** A caterpillar moults four or five times, and the early stages frequently look nothing like the last one. Eastern tiger swallowtail larvae start out brown and white as convincing bird droppings and finish as fat green snake-mimics. Black swallowtails begin black with a white saddle. If your caterpillar is under a centimetre, expect the field-guide picture to be wrong for it.

**Colour morphs.** Many species come in more than one colour with no other difference. Spicebush swallowtails turn yellow-orange before pupating. Buck moths and armyworms range from pale green to near-black depending on density and temperature. Colour is the weakest of the four filters here for exactly this reason, and it is the one most people start with.

**Parasitism.** A hornworm covered in what look like grains of white rice is carrying the cocoons of a braconid wasp that has been eating it from the inside. It is still a hornworm, it will not survive, and gardeners should leave it in place — those wasps are the most effective hornworm control available.

## What it will turn into, and whether that changes anything

The single most common follow-up question is whether the caterpillar becomes a butterfly or a moth. In practice the distinction runs almost exactly along the line this key already uses.

**Smooth, naked caterpillars** — swallowtails, monarchs, cabbageworms, loopers — become butterflies and moths in roughly equal numbers, and they pupate either as a naked chrysalis attached by a silk button and girdle, or underground.

**Hairy, tufted and spiny-with-hair caterpillars** are almost always moths. Butterflies with spiny larvae exist — fritillaries, mourning cloaks, question marks — but no North American butterfly has a furry caterpillar. So a fuzzy caterpillar is a moth, essentially without exception.

Whether it matters depends on why you are asking. For a gardener, the practical split is between the handful of species that actually damage a crop — hornworms, cabbageworms, loopers, armyworms, cutworms — and the great majority that eat a few leaves off a tree that does not notice. Tent caterpillars and fall webworms look catastrophic and are, in a healthy tree, cosmetic. Removing them by hand or with a jet of water is sufficient; spraying a whole tree to control webworm kills the parasitoid wasps that would have done it for you next year.

## Rearing one, if you want to see what it becomes

Raising a caterpillar to adulthood is the most reliable identification method available, and it takes two to four weeks for most species. Four things matter and the rest is detail.

1. **The right host plant, fresh, every day.** Most caterpillars will starve rather than switch. Take the plant it was found on, and if you do not know what that was, this is not going to work.
2. **Ventilation and no standing water.** A jar with a mesh lid beats a sealed container. Condensation kills more reared caterpillars than anything else, and mouldy frass is close behind — clean the container daily.
3. **Somewhere to pupate.** A twig to hang from, or a few centimetres of slightly damp soil or leaf litter for the many species that pupate underground.
4. **Cool for the winter.** A caterpillar collected in autumn will usually overwinter as a pupa and needs a genuinely cold spell — an unheated shed or garage — before it will emerge. Kept warm indoors it either emerges in December and dies, or never emerges at all.

Release the adult where you found the larva, and do not move species between regions. If you did not collect it locally, it should not be released at all.

## What this key covers

34 entries covering the species people in North America actually find: garden pests, the conspicuous large moths, the tent-builders, the stingers, and the butterflies whose larvae are recognisable. North America has over 11,000 moth and butterfly species and the great majority have caterpillars that are small, brown, nocturnal and separable only by an expert with a key and a microscope.

So a specimen that matches nothing here is far more likely to be one of the thousands of unremarkable noctuid and geometrid larvae than something rare. If it matters — a crop problem, a sting, a school project — photograph it in place with the host plant visible and something for scale, and submit it to BugGuide or iNaturalist, where regional specialists identify submissions for free. Include what plant it was eating; without that, even an expert is guessing.

## What the observation record shows

Every entry in this key that carries a scientific name is matched against

- [GBIF](https://www.gbif.org/), the
international register of biodiversity records, and against

- [iNaturalist](https://www.inaturalist.org/).
That puts a hard number behind 34 of the 34caterpillars here:
**5,886,602 georeferenced records** across the 32 entries that resolve to a single species, spanning 12 families, the oldest of them collected in
1958. The snapshot was taken on 2026-09-04.

That evidence is not spread evenly, and it is worth knowing before you trust a narrow
result. The five best-recorded caterpillars in this key hold 85%
of all the records between them: Imported cabbageworm alone accounts for
3,687,718, while Buck moth caterpillar has
1,061. A common thing is common in the data too, so
when a filter narrows to one frequent entry and one rare one, the frequent one is
usually the answer — and the record count is the quickest way to see which is which.
The same skew applies geographically: 37% of these
records come from the United Kingdom, so the key describes what is
reported there far better than it describes anywhere else.

### When these are actually reported

*Half of the 5,326,098 georeferenced records for these 32 caterpillars fall in July–August alone. The bars are the raw share by month, which mostly measures when people go looking; the line divides each month by the baseline for every species in every Orvik key, so a value above 1.0 means these caterpillars are reported more than the season alone explains, and it peaks in August. Source: GBIF, snapshot 2026-09-04.*

Half of every record for this group falls in July–August.
A raw month count measures two things at once — when the organism is about, and when
people are outdoors with a camera — and the second effect is large enough to give
almost anything a summer peak. The line on the figure divides each month by the
baseline for every species in every Orvik key, which answers a different question:
relative to when people record anything at all, when are these caterpillars recorded?
Values above 1.0 are the months that belong to this group rather than to the season.
On that measure 20 of the 32caterpillars here peak
outside the warm half of the year — Monarch, Eastern tiger swallowtail, Black swallowtail among them. Those are the ones a seasonal rule of
thumb gets wrong.

### Records behind each entry

Sorted by how much evidence exists, not by how likely you are to meet one. The peak
month is the effort-adjusted figure, and it is left blank wherever the sample is too
thin for the month-to-month wobble to mean anything.

*GBIF and iNaturalist record counts for the 34 named caterpillars in this key,
 snapshot 2026-09-04. Rows above species rank aggregate everything beneath them and
 are not comparable with the rest. Free to reuse with a link to this page.*

| Entry | Accepted name | Rank | GBIF records | Research-grade | Half fall in | Peak, adjusted | Most reported from |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Imported cabbageworm | [Pieris rapae](https://www.gbif.org/species/1920496) | species | 3,687,718 | 262,993 | Jul–Aug | July | the United Kingdom |
| Monarch | [Danaus plexippus](https://www.gbif.org/species/5133088) | species | 799,895 | 532,510 | Jul–Sep | January | the United States |
| Mourning cloak caterpillar | [Nymphalis antiopa](https://www.gbif.org/species/5130682) | species | 247,233 | 96,125 | Apr–Jun | April | Finland |
| Spongy moth | [Lymantria dispar Linnaeus, 1758](https://www.gbif.org/species/1820406) | species | 146,176 | 83,343 | Jun–Jul | June | the Netherlands |
| Eastern tiger swallowtail | [Papilio glaucus Linnaeus, 1758](https://www.gbif.org/species/1938016) | species | 127,549 | 207,099 | Jul–Aug | March | the United States |
| Black swallowtail | [Papilio polyxenes Fabricius, 1775](https://www.gbif.org/species/1937816) | species | 118,300 | 142,960 | Jun–Aug | February | the United States |
| Woolly bear | [Pyrrharctia isabella J.E.Smith, 1797](https://www.gbif.org/species/1807881) | species | 73,490 | 102,854 | Aug–Oct | October | the United States |
| Great spangled fritillary caterpillar | [Speyeria cybele](https://www.gbif.org/species/1905172) | species | 62,911 | — | Jun–Jul | June | the United States |
| Viceroy caterpillar | [Limenitis archippus Cramer, 1775](https://www.gbif.org/species/5132398) | species | 54,362 | 51,860 | Jul–Aug | June | the United States |
| Polyphemus moth caterpillar | [Antheraea polyphemus Cramer, 1775](https://www.gbif.org/species/1866570) | species | 53,407 | 80,988 | May–Jul | February | the United States |
| Spicebush swallowtail | [Papilio troilus Linnaeus, 1758](https://www.gbif.org/species/1938104) | species | 50,421 | 65,707 | Jul–Aug | March | the United States |
| Fall webworm | [Hyphantria cunea](https://www.gbif.org/species/1817797) | species | 50,172 | 78,851 | Jun–Aug | November | the United States |
| Luna moth caterpillar | [Actias luna Linnaeus, 1758](https://www.gbif.org/species/1865668) | species | 47,535 | 69,812 | May–Jul | March | the United States |
| Eastern tent caterpillar | [Malacosoma americana](https://www.gbif.org/species/5715280) | species | 46,809 | 66,138 | Apr–May | April | the United States |
| Hickory tussock moth | [Lophocampa caryae Harris, 1841](https://www.gbif.org/species/1817732) | species | 41,768 | 60,314 | Aug–Sep | October | the United States |
| Yellow woolly bear | [Spilosoma virginica Fabricius, 1798](https://www.gbif.org/species/1811948) | species | 39,530 | 73,822 | Jun–Aug | October | the United States |
| Milkweed tussock moth | [Euchaetes egle Drury, 1773](https://www.gbif.org/species/5116353) | species | 31,712 | 47,522 | Aug–Aug | August | the United States |
| Forest tent caterpillar | [Malacosoma disstria Hübner](https://www.gbif.org/species/5101763) | species | 29,306 | 41,719 | Apr–Jun | April | the United States |
| Io moth caterpillar | [Automeris io Fabricius, 1775](https://www.gbif.org/species/1866085) | species | 24,812 | 33,351 | May–Jul | December | the United States |
| White-marked tussock moth | [Orgyia leucostigma J.E.Smith, 1797](https://www.gbif.org/species/5925317) | species | 24,554 | 42,821 | Jun–Aug | October | the United States |
| Hummingbird moth caterpillar | [Hemaris thysbe Fabricius, 1775](https://www.gbif.org/species/1861851) | species | 21,951 | 30,581 | Jun–Jul | July | the United States |
| Tobacco hornworm | [Manduca sexta Linnaeus, 1763](https://www.gbif.org/species/1863978) | species | 21,557 | 33,018 | Jul–Aug | October | the United States |
| Cecropia moth caterpillar | [Hyalophora cecropia Linnaeus, 1758](https://www.gbif.org/species/1865839) | species | 13,844 | 20,547 | Apr–Jun | February | the United States |
| Fall armyworm | [Spodoptera frugiperda J.E.Smith, 1797](https://www.gbif.org/species/5109855) | species | 13,635 | 23,372 | Jul–Sep | November | the United States |
| Bagworm | [Thyridopteryx ephemeraeformis](https://www.gbif.org/species/1853312) | species | 10,695 | 18,740 | May–Sep | February | the United States |
| Puss caterpillar | [Megalopyge opercularis](https://www.gbif.org/species/1751572) | species | 9,349 | 13,461 | Apr–Jul | November | the United States |
| Cabbage looper | [Trichoplusia ni](https://www.gbif.org/species/1786360) | species | 8,810 | 5,600 | Jun–Aug | November | the United States |
| Spiny oak slug | [Euclea delphinii](https://www.gbif.org/species/5105365) | species | 8,443 | 10,830 | Jun–Jul | June | the United States |
| Catalpa sphinx | [Ceratomia catalpae Boisduval](https://www.gbif.org/species/1861892) | species | 6,932 | 10,617 | Jul–Aug | September | the United States |
| Saddleback caterpillar | [Acharia stimulea](https://www.gbif.org/species/9776414) | species | 6,702 | 10,281 | Jul–Aug | September | the United States |
| Tomato hornworm | [Manduca quinquemaculatus Haworth, 1803](https://www.gbif.org/species/1864008) | species | 5,963 | 7,530 | Jun–Aug | October | the United States |
| Buck moth caterpillar | [Hemileuca maia Drury, 1773](https://www.gbif.org/species/1865313) | species | 1,061 | 13,677 | Sep–Oct | October | the United States |
| Inchworm or cankerworm | [Geometridae](https://www.gbif.org/species/6950) | family | 24,385,819 | 4,540,304 | May–Jul | February | the United Kingdom |
| Cutworm | [Agrotis Ochsenheimer, 1816](https://www.gbif.org/species/8407958) | genus | 1,987,359 | 159,012 | Jun–Jul | June | the United Kingdom |

This table is assembled from open data and is free to reuse with a link back to this
page. The snapshot behind every Orvik key is published as one downloadable file on the

- [open field data](https://orvik.app/data/) page, with each source's licence terms.

## Questions people ask about this

Which caterpillars sting?

In North America the ones that matter are the puss caterpillar, saddleback, io moth, buck moth and the slug caterpillars including the spiny oak slug. Tussock moths and spongy moth cause an itchy rash rather than a true sting. The visual warning signs are branched spines, a slug-like body with no visible head, or dense soft-looking fur — and the safe rule is simply not to pick up any caterpillar that has spines, tufts or fur.

What is the big green caterpillar on my tomato plants?

A hornworm. If it has seven straight white diagonal stripes and a red horn, it is a tobacco hornworm; eight white V-shapes and a dark blue-black horn make it a tomato hornworm. Both eat tomatoes despite the names. If it is studded with white rice-like grains, those are braconid wasp cocoons — leave that one in place, because the wasps emerging from it will control the next generation.

What are the caterpillars in a web in my tree?

In spring, a dense silk tent in the fork of a wild cherry or apple branch is eastern tent caterpillar; the larvae leave the tent to feed. In late summer, a loose grey web wrapping the leaves at the tip of a branch is fall webworm; those feed inside the web. Both look worse than they are — a healthy tree tolerates the defoliation, and pruning out the tent or blasting it with a hose is enough.

Does the woolly bear's brown band really predict the winter?

No. The width of the rust-coloured band tracks the caterpillar's age and how wet the previous growing season was: the band widens with each moult, so an older, better-fed caterpillar has a wider band. The folklore was tested by an American Museum of Natural History curator in the 1940s and has never held up since.

How do I tell a moth caterpillar from a butterfly caterpillar?

The reliable rule in North America is that no butterfly has a hairy or furry caterpillar, so anything fuzzy is a moth. Butterflies do have spiny caterpillars — fritillaries, mourning cloaks and question marks all do — so spines alone are not the test. Beyond that, moth caterpillars often spin a silk cocoon while butterfly larvae form a naked chrysalis.

Why does my caterpillar look nothing like the pictures?

Most likely because it is an early instar. Caterpillars moult four or five times and can change appearance completely: eastern tiger swallowtails start as brown-and-white bird-dropping mimics and end as fat green snake-mimics. Colour morphs are the other cause — armyworms, buck moths and many others vary from pale green to near-black within one species. Filter by host plant and texture rather than by colour when the picture will not match.

What do I feed a caterpillar I found?

The plant you found it on, fresh, every day. Most caterpillars are restricted to one plant family and will starve rather than switch, so if the host is unknown the honest answer is to put it back where you found it. Keep the container ventilated rather than sealed, clean the droppings daily, and give it a twig or a few centimetres of damp soil to pupate in.

## Still not sure? Point a camera at it

A filter narrows caterpillars down to a shortlist. Orvik reads the photo itself and names the species, with the look-alikes ranked underneath so you can check the call yourself.

- [Get Orvik free](https://orvik.app/app/)

## Keep reading on Orvik

- [Types of caterpillars, with pictures](https://orvik.app/insects/types-of-caterpillars/)

- [How caterpillar identification works](https://orvik.app/insects/caterpillar-identifier/)

- [Larvae identification chart](https://orvik.app/insects/larvae-identification-chart/)

- [Moth identification](https://orvik.app/insects/moth-identification/)

- [Grub identification](https://orvik.app/insects/grub-identification/)

- [What type of bug is this?](https://orvik.app/insects/what-type-of-bug-is-this/)

- [Identify a bug by photo](https://orvik.app/insects/identify-bug-by-photo/)

- [Identify a plant by leaf shape](https://orvik.app/plants/identify-plant-by-leaf-shape/)

## Other free Orvik tools

- [What spider is this?](https://orvik.app/tools/spider-identifier/)
- [What beetle is this?](https://orvik.app/tools/beetle-identifier/)
- [Is that a butterfly or a moth, and which one?](https://orvik.app/tools/butterfly-moth-identifier/)
- [What mushroom is this?](https://orvik.app/tools/mushroom-identifier/)
- [What cloud is that?](https://orvik.app/tools/cloud-identifier/)
- [What shell did I find on the beach?](https://orvik.app/tools/seashell-identifier/)
- [What kind of arrowhead did I find?](https://orvik.app/tools/arrowhead-identifier/)
- [How old is this tree?](https://orvik.app/tools/tree-age-calculator/)

## Where the data comes from

- [Moth Photographers Group — Lepidoptera plates by species](https://mothphotographersgroup.msstate.edu/)
- [University of Florida IFAS — stinging caterpillars of Florida](https://entnemdept.ufl.edu/creatures/misc/stinging_caterpillars.htm)
- [USDA Forest Service — forest insect and disease leaflets](https://www.fs.usda.gov/foresthealth/publications/index.shtml)
- [Wagner, D. — Caterpillars of Eastern North America (Princeton)](https://press.princeton.edu/books/paperback/9780691121444/caterpillars-of-eastern-north-america)
- [GBIF — Global Biodiversity Information Facility](https://www.gbif.org/)
- [iNaturalist](https://www.inaturalist.org/)

---

HTML version: https://orvik.app/tools/caterpillar-identifier/
Structured data for this site: https://orvik.app/api/v1/openapi.json · https://orvik.app/llms.txt
Free to quote and reuse with a link back to the source URL above (CC BY 4.0).