Many caterpillars have setae and spines. Only a few species, though, have hair that can actually sting. If you cannot tell the venomous ones apart, it is safest to avoid touching them. Caterpillars are a key stage in the life cycle of butterflies and moths. That life cycle has four stages: eggs, caterpillars (larvae), pupae, and adults.
Caterpillars are the larval stage of butterflies and moths. Other insects also have larval stages, and some of those larvae look a lot like caterpillars, which can make telling them apart tricky. On top of that, the huge number of butterfly and moth species means identifying exactly which caterpillar you have found can be a real challenge.
🔎 Quick ID, what did you find?
Tap an answer in each row. We will tell you what the color and texture are usually telling you, then scroll the family field guide below to match a photo.
1. What color is it?
2. What is the texture?
3. How does it move or rest?
How to Identify a Caterpillar
- In general, almost all caterpillars have some common physical features.
- They have tubular bodies, which are segmented.
- Most of them have three pairs of true legs on their thoracic segments.
- The number and location of prolegs on the abdominal segments may differ from one type to another.
- Some types of caterpillars have their bodies covered with hair.
Muscular Body
Studies show that a caterpillar has around 4000 muscles in its body. It moves by squeezing the muscles in its rear segments forward in a wave, almost like a slow ripple running along its body.
How Do Caterpillars Breathe?
Butterfly larvae breathe through tiny holes called spiracles. These are spaced along the sides of their thoracic and abdominal segments. Some caterpillars even have gills, so they can live underwater.
Can Caterpillars See?
Yes! Caterpillars have around six small eyelets on each side of their head. They are not very sharp-sighted, but they can detect light and movement well enough to find their way around.
How Do Caterpillars Feed?
Caterpillars use their antennae to sense vibrations and track down food. Their jaws are strong enough to chew through tough leaves. Most caterpillars eat plant matter, but some species eat other insects.
Caterpillars, Worms, and Other Insect Larvae
- Caterpillars and worms both have soft bodies, but caterpillars have legs and worms do not.
- Another clue is the prolegs. Most insect larvae other than caterpillars have prolegs on nearly every body segment. Caterpillars only have them on a few.
- Caterpillars usually have five pairs of prolegs on their abdominal segments. Each proleg has tiny grasping hooks, a feature that other insect larvae do not have.
Frequently Asked Questions
What is a caterpillar?
A caterpillar is the larva (the baby stage) of a butterfly or a moth. The life cycle has four stages: egg, caterpillar, pupa, and adult.
How many legs does a caterpillar have?
Most caterpillars have three pairs of true legs on the thoracic segments near the head, plus several pairs of soft gripping prolegs along the abdomen, usually five pairs.
How can you tell a caterpillar from a worm?
Caterpillars have legs and grasping hooks on their prolegs; worms have no legs at all. Other insect larvae usually have prolegs on every body segment, while caterpillars have them on only a few.
Are caterpillars with a horn dangerous?
No. The horn on a hornworm is not a stinger and cannot hurt you. It mimics a real thorn and helps camouflage the caterpillar.
Which caterpillars should you not touch?
Caterpillars that are distinctively colored or covered in dense hair or spines may sting. The safe rule is to look but not touch the hairy or brightly colored ones.
A Field Guide to Caterpillar Families
Identifying a caterpillar is not easy. The order Lepidoptera (which includes all butterflies and moths) has more than 150,000 species spread across 126 families. No one can know every single one. Some caterpillars have dense hair, others have warts, spikes, spots, or stripes. Some are only found on certain plants. A good starting point is to work out which family a caterpillar belongs to. The families below are a great place to start, once you spot the family, you are well on your way to a name, and to knowing which moth or butterfly it will become.
Inchworms & Loopers (Thysanopyga intractata)
Members of this family are called geometer moths. Their larvae are known as inchworms, spanworms, or loopers, names that come from the way they move. When an inchworm crawls, it looks as if it is measuring the surface beneath it.
Physical Characteristics
Unlike most caterpillars, loopers have their prolegs bunched at both ends of their bodies. They grip with their front and back ends and pull their middle into a loop as they inch forward. Most are green, gray, or brown, great colors for hiding on leaves and bark. When threatened, some stand perfectly still and straight, pretending to be a twig.
Skipper Larvae
The name "skipper" comes from the darting flight of the adult butterflies in this family. The caterpillars of the Hesperiidae family are easier to recognize once you know what to look for. Most skipper larvae have large heads and a noticeably narrow neck. The body is widest near the abdomen and tapers toward the back end.
Physical Characteristics
Skipper caterpillars have a special anal comb, a tiny structure that flicks waste away from their shelter and feeding spots. The ring-like body segments are covered in fine hair. Most are active at night and build shelters by rolling or folding leaves around themselves. They usually have a single, plain body color.
Hornworms (Mimas tiliae)
Caterpillars of hawk moths in the Sphingidae family are called hornworms. Their name comes from the horn-like spike at the back end of the abdomen, usually on the eighth abdominal segment. Every segment along the body has shallow diagonal creases.
Physical Characteristics
The anal prolegs of a hornworm are flat and form a triangle under the anal plate. When it is time to pupate, most hornworms climb down to the ground and burrow in. They are among the largest and most common caterpillars in many parts of the world.
Hickory Horned Devils (Citheronia regalis, Antheraea polyphemus)
The Saturniidae family includes some of the largest caterpillars in the world, many with long setae, dramatic horns, and knobbly bumps. The caterpillars of regal moths (Citheronia regalis), which belong to the subfamily Ceratocampinae, are called hickory horned devils, and they live up to that name.
Physical Characteristics
A silk moth caterpillar can grow to around 3 to 4 inches long. Most have scoli (branched, thickened spines) running along their back and sides. They live in trees and shrubs. In late summer they come down to the ground, burrow into leaf debris, and spin cocoons that can be used to make silk. However, the silk is not as fine as that produced by Bombyx Mori.
Take the Caterpillar Detective Quiz!
5 quick questions straight from this guide. Find out how sharp your caterpillar eye really is.
Swallowtail Caterpillars (Papilio polyxenes)
The Papilionidae family contains some of the largest and most colorful butterflies in the world. Their common name, swallowtails, comes from the forked shape of their hind wings. The caterpillars are mostly brightly colored and covered in very fine hair.
Physical Characteristics
The most famous feature of a swallowtail caterpillar is the osmeterium, a forked, fleshy organ that hides behind the head in the second body segment. When a predator comes too close, the caterpillar pops it out and releases a foul smell to drive the attacker away. The widest part of a swallowtail caterpillar's body is where the thorax meets the abdomen.
Tussock Moth Caterpillars (Halysidota tessellaris)
The tussock moth gets its name from the dense tufts of hair on its larvae. Most tussock moth caterpillars are striking and easy to recognize, with bunches of hair sticking out in all directions. Those hairs come off very easily and can cause a rash or allergic reaction if they touch your skin, that is their defense. Even the cocoons are woven with the caterpillar's own body hair.
Woolly Bears (Pyrrharctia isabella)
Tiger moths belong to the family Arctiidae. Their caterpillars are often called woolly bears or woolly worms, because of the thick hair that covers their bodies. Not all members of this family are hairy, larvae of lichen moth species feed on lichens and moss and are mostly bare. Most tiger moth caterpillars have brightly colored bodies. They are easiest to spot in fall, when they wander around looking for a good spot to hibernate.
Physical Characteristics
Woolly bears enjoy basking in the sun to warm up and speed up digestion. When threatened, most of them curl up tightly into a ball. Lichen moth caterpillars are dark-colored with dark hair. Some have extra tufts of hair along their back. (Note: some caterpillars are also called tussock moths, but that name properly belongs to the family Lymantriidae.)
Prominents (Stauropus fagi)
Prominents are a family of large moths. Their common name comes from the tufts that stick up from the wings of adults, and from the raised humps on the backs of their larvae. Most prominent caterpillars have colorful, smooth (hairless) bodies with bumps, spines, or humps. Some can squirt acid from a gland on the underside of their thorax to drive off attackers.
Physical Characteristics
Not every species uses that acid defense. Prominent caterpillars have extra setae above the prolegs in the middle of their abdomen. The anal prolegs are either very short or very long and tail-like. When resting, most prominents hold both ends of their body raised off the surface, a posture that makes them fairly easy to spot.
Slug Caterpillars (Acharia stimulea)
The Limacodidae family has some of the most unusual-looking caterpillars of all. They are called slug moth caterpillars because their flat, oval bodies look a lot like slugs. The family is also known as cup moths, from the cup-shaped cocoons they spin. Most species have flat-bodied larvae with sucker-like pads where normal prolegs would be.
Physical Characteristics
Slug caterpillars are usually green and smooth, and they glide along in a gentle wavy motion. Other species in this family, however, are brightly colored and armed with tubercles and stinging (urticating) hair, a reminder to look but not touch. Most slug caterpillars keep their head tucked out of sight inside a fold of the thorax.
Tent Caterpillars (Malacosoma californicum)
This moth family has around 200 species. The adults are also called snout moths (from their pointed snouts) or eggars (from their egg-shaped cocoons). The hairy caterpillars of these species have flaps of skin over their prolegs, which is why they are also known as lappet moths. Hair is mostly concentrated along the sides of the body. In some species, caterpillars build big communal nests of silk in tree forks and live inside them together, giving rise to the name tent caterpillars.
Cutworms (Acronicta psi, Colocasia coryli)
Noctuidae is the largest family in the order Lepidoptera. Their larvae are called cutworms. With around 35,000 known species, the caterpillars in this family are so varied that it is hard to list features they all share. In general, they tend to have sturdy, chunky bodies and setae that are hard to see. A few species are hairy, a bit like tiger moth caterpillars.
This is only a brief overview of some commonly found caterpillars, sorted by family. The best way to get really good at identification is to learn about the species in your local area, especially any that are crop pests or are venomous. The more caterpillars you watch in the garden, the quicker the clues start to click into place.
Explore More Animals
Types of Moths: A Guide to the 9 Major FamiliesMoths make up 90% of Lepidoptera, and most species are still unnamed. Meet the 9 major moth families, from silk-spinning Bombycidae to the hovering hawk-moths
Green Caterpillar IdentificationHow to identify a green caterpillar by its shade, body pattern, hair and unique features, with pictures of the luna moth, hornworms, swallowtails and more.
An Awesome Explanation of the Life Cycle of a CaterpillarThe caterpillar life cycle is explained in short in this article, along with some interesting facts about caterpillars.
5 Poisonous Caterpillars You Didn't Know AboutThink caterpillars are harmless? Think again. Meet 5 crazily poisonous caterpillars, from the fuzzy Puss Caterpillar to the spine-covered Io Moth Caterpillar,
Fun fact for today!The order Lepidoptera (moths and butterflies) has more than 150,000 species. That is why caterpillars come in so many shapes and colors!