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Caterpillars With Spines: A Quick and Easy Guide (With Photos)

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Read on and learn to identify spiny caterpillars. Pictured above is the zebra butterfly's very spiny caterpillar.

Read on and learn to identify spiny caterpillars. Pictured above is the zebra butterfly's very spiny caterpillar.

Identification of Caterpillars With Spines

The caterpillars in this guide all have one thing in common: spines. Some, like the stinging buck moth caterpillar, are covered with dense, branching spines; others, like the fearsome hickory horned devil, have only a few (but the few it does have are pretty impressive).

The insects described in this guide are all the larvae of Lepidoptera species—that is, butterflies and moths. There is about an even split between moth and butterfly species; in fact, spiny species are likely to be either moth or butterfly, with no particular way of telling the difference at first glance.

All of these species can be raised to adulthood if you choose, except for the gypsy moth caterpillar, an invasive species that is actually illegal to propagate intentionally. The buck and io moth caterpillars possess a significant sting, so if you decide to raise or handle these caterpillars, please use caution!

Here are the 15 caterpillars this guide covers:

  1. The Io Moth
  2. The Gypsy Moth
  3. The Regal Moth
  4. The Mourning Cloak Butterfly
  5. The Saddleback Caterpillar
  6. The Giant Leopard Moth Caterpillar
  7. Buck Moths
  8. The Painted Lady Butterfly
  9. The Red Admiral
  10. Fritillary Caterpillars
  11. The Smeared Dagger Moth
  12. The Gulf Fritillary
  13. The Variegated Fritillary
  14. Zebra Longiwng Butterfly
  15. The Question Mark
The io moth caterpillar is covered with venomous spines

The io moth caterpillar is covered with venomous spines

1. The Io Moth

The io moth (Automeris io) belongs to the group of giant silk moths that includes the cecropia and polyphemus moths, whose larvae have a few spines, but nothing like the io.

This is one of the few caterpillars in our area that has stinging spines, and contact with them results in a sting not unlike a honey bee—that is, painful but not serious. This species is related to the buck moth, which has a more potent sting.

This beautiful caterpillar turns into a beautiful moth. The false eyespots on the hind wing are very realistic and come complete with reflected-light markings, making them extra realistic.

The Basics:

  • Does it sting? Yes. This species protects itself with venomous spines
  • What does it eat? Birch, willow, dogwood, ash and many more trees
  • Will it seriously damage plants or trees? Not usually an issue
  • Is it rare? No, but it is not seen very often
  • What does it turn into? The striking io giant silk moth
  • Can you raise it to an adult? Yes, but be very careful when handling this species
The spiny caterpillar of the gypsy moth is a major pest of forests

The spiny caterpillar of the gypsy moth is a major pest of forests

2. The Gyspy Moth

The gypsy moth (Lymantria dispar) is an introduced species that has caused real havoc in areas where it has spread. It can multiply out of control and strip entire trees down to the branch in some places.

In some cases, whole forests lose their leaves to hordes of these caterpillars. If you walk into a forest under attack from gypsy moth caterpillars, you will hear millions of tiny jaws munching away on the leaves and feel a steady light rain of caterpillar poops.

Attempts have been made to control this caterpillar by spraying infested forests with a kind of bacteria that kills the caterpillars, which works, but sometimes too well—the bacteria also attacks innocent non-pest species. In some cases, this control method proves to be worse than the actual infestation.

The Basics:

  • Does it sting? No, although the spines are sharp and stiff
  • What does it eat? Everything, and a lot of it
  • Will it seriously damage plants or trees? Yes—this is one of the most serious insect pests on the planet
  • Is it rare? No
  • What does it turn into? The gypsy moth
  • Can you raise it to an adult? Raising this species is actually illegal in some areas
The very spiny caterpillar of the regal moth is one of the largest in the world -- this is a small one!

The very spiny caterpillar of the regal moth is one of the largest in the world -- this is a small one!

3. The Regal Moth

The regal moth caterpillar (Citheronia regalis) is perhaps the spiniest of all the species listed in this guide, which is saying something. It's known as the "hickory horned devil," and it truly earns that name—it looks like a miniature dragon.

Aside from the sharp black spines that occur on every body segment, the hickory horned devil has several huge curved red-and-black horns on its foremost segments. Combine this with the huge size of the insect. At over six inches, it's one of the largest caterpillars anywhere on the planet—according to some sources, it's the biggest caterpillar in the entire world. The hickory horned devil is likely the largest and fiercest-looking caterpillar in North America. Full-grown, they are nearly half a foot long and will rear up and make a clicking sound if you bother them.

Amazingly, hickory horned devils are totally harmless—all those fierce horns and spines are only for show.

The hickory horned devil turns into the regal moth, a gigantic, beautiful insect that most people will never see in nature.

The Basics:

  • Does it sting? No, even though it looks really fierce
  • What does it eat? Walnut, oak, persimmon, and hickory
  • Will it seriously damage plants or trees? Not usually
  • Is it rare? Common the American South
  • What does it turn into? A huge, beautiful moth, it's the biggest in North America in terms of mass
  • Can you raise it to an adult? Yes, although it pupates in soil (no cocoon)
The mourning cloak butterfly has a spiny caterpillar that eats elms and other plants

The mourning cloak butterfly has a spiny caterpillar that eats elms and other plants

4. The Mourning Cloak Butterfly

The Mourning Cloak Butterfly caterpillar (Nymphalis antiopa) eats elm leaves and is known in some places as "the spiny elm caterpillar." It is the larval stage of one of the best-known butterflies in the world, the mourning cloak. This beautiful insect is native to the US and Europe. This species is incredibly rare in the UK, and entomologists can spend a lifetime waiting for one to show up (it's known as "the Camberwell Beauty" in England).

Up close, the upper side of the mourning cloak is gorgeous. The underside is considerably drabber; the dark colors give the insect its common name because early entomologists thought it looked like the drab cloaks worn by mourners at funerals.

Mourning cloaks often winter in a shelter and begin flying on the first warm days of spring. Keep an eye out for these big, beautiful butterflies on warm spring days, even when there are still patches of snow on the ground.

The Basics:

  • Does it sting? No, although the spines are sharp
  • What does it eat? Elm leaves
  • Will it seriously damage plants or trees? Not usually
  • Is it rare? Not in North America, but in England, it is very rare
  • What does it turn into? A gorgeous burgundy and yellow butterfly
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves
The saddleback caterpillar has stinging spines

The saddleback caterpillar has stinging spines

5. The Saddleback Caterpillar

The Saddleback Caterpillar (Acharia stimulea) species belongs to the family Limacodidae, a group of moths better known as caterpillars. They move with suction-cup feet and sort of glide along and are therefore commonly known as "slug caterpillars."

Nearly all of them can sting, even though their spines and hairs are not always noticeable. The stinging rose caterpillar is one of them, as is the spine oak slug. There are many others, some of which have truly bizarre appearances.

For true spines, though, the saddleback caterpillar has them all beat. It has obvious spines protruding from four fleshy tubercles. These spines bear a kind of venom that causes welts, pain, and itching when touched. Stay away from the spines, and you'll be safe—like all caterpillars, saddlebacks move slowly and cannot fling or launch their spines, or themselves, at you or anything else.

The moth of this interesting species is a pretty chocolate brown, with tan and green markings. It is very seldom seen.

The Basics:

  • Scientific name: Acharia stimulea
  • Food Plant: an extensive variety of plants, including maple, dogwood, pecan, and crepe myrtle
  • Range: Southeastern US
  • Adult Moth: The adult is small and stout with dark-brown wings
  • Severity of Sting: This caterpillar has a sharp, painful sting, similar to a honeybee
The spiny caterpillar of the giant leapord moth shows bright crimson bands when it rolls up

The spiny caterpillar of the giant leapord moth shows bright crimson bands when it rolls up

6. The Giant Leopard Moth Caterpillar

The giant leopard moth caterpillar (Hypercompe scribonia) is likely the spiniest in this guide. It is covered in sharp, stiff spines that have the feel of sharp needles—they are not venomous, but the effect of so many truly sharp, stiff spines makes handling a giant leopard moth caterpillar somewhat hazardous. When it rolls into a ball, it shows bright crimson bands between its body segments.

This large caterpillar can sometimes be found curled up under stones or logs, where it overwinters. The adult moth is one of the most beautiful insects in North America.

The Basics:

  • Scientific name: Hypercompe scribonia
  • Food Plant: Many low plants, including plantain
  • Range: Ranges across the US and into Canada; similar species south into Mexico
  • Adult Moth: The adult moths are large, beautiful insects
  • Severity of Sting: Does not sting, but the spines are surprisingly stiff and sharp
The spiny caterpillar of the buck moth has a venomous sting

The spiny caterpillar of the buck moth has a venomous sting

7. Buck Moths

There are several closely related moths in the genus Hemileuca, and the larvae of all of them can sting—they are known collectively as "buck moths." On occasion, they will undergo a population explosion; at these times, they will be found crawling around on the ground and gathering in large mats of several dozen individuals on tree trunks. This provides the species with increased protection from predators since an encounter with a large number of this stinging caterpillar is a truly intimidating event.

Buck moths are related to the io moth, which also has several less-well-known species and sub-species. In general, it's best to be cautious around caterpillars with bright colors and multiple sets of rosette spines.

The Basics:

  • Scientific name: Hemileuca species
  • Food Plant: Mostly oaks
  • Range: Several species, ranging across the US and into Canada and Mexico
  • Adult Moth: The adult moths are large, beautiful insects
  • Severity of Sting: Can be very painful, especially if you contact a group of the caterpillars
The painted lady caterpillar makes a nest in nettles

The painted lady caterpillar makes a nest in nettles

8. The Painted Lady Butterfly

If you buy a commercially available butterfly raising kit, the painted lady butterfly (Vanessa cardui) is the species you will most likely get. One reason for this is that the species is distributed worldwide, so releasing them into nature once they have hatched out is not an issue. Another reason is that they do very well in captivity and will thrive eating the mixture provided with the kit.

In the wild, painted lady butterflies occur in almost all parts of the world. They are thought to mimic monarchs, and they show the red and black warning colors that are thought to signal "danger" to predators like birds and lizards.

The spiny caterpillar of Vanessa cardui is totally harmless. It has no venom or other chemical protection that would affect humans.

The Basics:

  • Scientific name: Vanessa cardui
  • Food Plant: Thistle and hollyhock
  • Range: Essentially worldwide
  • Adult: The adult butterflies are large, beautiful insects
  • Can You Raise it to the Adult: Yes, this species is very easy to raise
The red admiral caterpillar showing its spines

The red admiral caterpillar showing its spines

9. The Red Admiral

The Red Admiral (Vanessa atalanta) is a very common species and is one of the most often-seen butterflies in urban areas. It has a quick and nervous flight, but it lands frequently; males will often patrol areas around porches and yards in the late afternoon, returning to the same perch after each tour of its territory. This butterfly is also well-known for its habit of landing on people, which it evidently regards as a suitable perch.

The caterpillar of this charming butterfly feed in groups on nettles. You will sometimes find their nest in the summer, with many individuals and a whole lot of poop as well. They likely gain some protection by making this stinging plant their home.

Red admiral caterpillars are dark, with jagged yellow markings on the side. Their black spines cover most of the body, making it even more difficult for a predator to get anything more than a mouthful of prickles should they decide to attack.

The Basics:

  • Does it sting? No, although the spines are sharp.
  • What does it eat? Nettles
  • Will it seriously damage plants or trees? Not usually.
  • Is it rare? No—this species is among the most common of North American butterflies
  • What does it turn into? A pretty red and black butterfly
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves
The spiny caterpillar of Edith's checkerspot is typical of the Nymphalidae family

The spiny caterpillar of Edith's checkerspot is typical of the Nymphalidae family

10. Fritillary Caterpillars

Taken as a group, fritillary caterpillars (genus speyeria and others) are uniformly spiny. There are many different kinds that fall under the umbrella of "fritillary," and even more if you include the checkerspots and crescents. These butterflies are generally orange with black spots and chevrons. Some have silvered spots on the underside. They are among the most beautiful insects in North America.

The great spangled fritillary, Speyeria cybele, is representative of the group. It flies throughout the Eastern United States in open spaces. The spiny caterpillar, which is dark-colored with many yellow-orange spines, feeds on violets and other low plants. It's unusual to find this caterpillar, but in my experience the species is far from rare.

The Basics:

  • Does it sting? No, although the spines are sharp
  • What does it eat? Violets and other plants
  • Will it seriously damage plants or trees? Not usually
  • Is it rare? No
  • What does it turn into? A pretty orange and black butterfly with silvered spots on the underside
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves
The smeared dagger moth has a very spiny caterpillar

The smeared dagger moth has a very spiny caterpillar

11. The Smeared Dagger Moth

The adult smeared dagger moth (Acronicta oblinita), like all dagger moths, is gray with black spots and chevrons, including a vaguely dagger-shaped mark at the lower corner of the upper wing; this is where the group gets its common name.

The spiny caterpillar of the smeared dagger moth feeds on many plants and is among the more common moth caterpillars in the eastern US. It has a characteristic jagged yellow line down its side, which makes it look quite similar to another spiny caterpillar in this guide, the red admiral butterfly.

This species is common enough that it can sometimes be considered a pest in the fruit industry due to the spiny caterpillar's ability to strip small trees of leaves if there are enough of them.

The Basics:

  • Does it sting? No, although the spines are sharp
  • What does it eat? Many plants and trees
  • Will it seriously damage plants or trees? Yes, occasionally
  • Is it rare? No
  • What does it turn into? A drab gray moth
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves
The beautiful spiny caterpillar of the gulf fritillary

The beautiful spiny caterpillar of the gulf fritillary

12. The Gulf Fritillary

The gulf fritillary (Agraulis vanillae) is a simply gorgeous butterfly, one of the most striking insects in North America. It has the orange and black upperside of most fritillary species, but underneath, it is shaded with crimson, rich coffee-brown, and bright metallic silver spots.

Interestingly, it is not a true fritillary; it's a member of a tropical group of butterflies sometimes called longwings or Heliconiids. There are no other members of this group that resemble the gulf fritillary. The group is well known for its mimicry of other species, so the gulf fritillary is likely "copying" the colors of true fritillaries to gain protection from predators. Of course, it could also be the other way around, an idea supported by the fact that Heliconiid caterpillars feed on vines—in this case, Passiflora vines—that are known to have toxic sap.

Whatever the case, the spiny caterpillar of the gulf fritillary, is sometimes found on passion flower vines, especially in Florida and Texas. It is a southern species, but is sometimes found as far north as the Great Lakes.

The Basics:

  • Does it sting? No, although the spines are sharp
  • What does it eat? Passion flower vines
  • Will it seriously damage plants or trees? Yes, it can occasionally remove the leaves from the host plant
  • Is it rare? Not in the South, but in the North, it is seldom seen
  • What does it turn into? A gorgeous butterfly
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves
The caterpillar of the variegated fritillary is covered in spines

The caterpillar of the variegated fritillary is covered in spines

13. The Variegated Fritillary

Like the gulf fritillary, the variegated fritillary (Euptoieta claudia) is not a true fritillary, despite superficially resembling members of that group. This butterfly is like a paler version of the gulf fritillary, with a "smeared" look to the underside and no metallic silver markings. While it is related to the true fritillaries, the variegated fritillary exhibits some distinct differences:

  • Variegated fritillaries have two or three broods per year vs. one per year in Speyeria
  • They are nomadic vs. sedentary
  • They use a wide range of host plants vs. just violets
  • Variegated fritillaries also have taxonomic links to the heliconians
  • Their flight is low and swift, rather than high and gliding

Another characteristic of this species is that they are very hard to approach; accordingly, its genus name was taken from the Greek word euptoietos, meaning "easily scared."

The beautiful spiny caterpillar becomes an even more beautiful pupa, marked with cream, orange, and metallic silver spines. The caterpillar's food plants include moonseed, flax, passionflower, plantain, pansy, and violets.

The Basics:

  • Does it sting? No, although the spines are sharp
  • What does it eat? Many plants (see above)
  • Will it seriously damage plants or trees? Not usually
  • Is it rare? No, although it is more common in the South
  • What does it turn into? A pretty orange and black butterfly
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves
spiny-caterpillar-identification

14. Zebra Longwing Butterfly

The Zebra Longwing Butterfly (Heliconius charithonia) is an unmistakable butterfly. It is not only the state butterfly of Florida, it's also one of the most striking and beautiful insects to be found in the American South. It generally flies in forests and overgrown areas, where its black-and-yellow stripes and slow, fluttering flight serve to announce to predators that it is toxic and should not be pursued.

The spiny caterpillar is whitish with long spines. It feeds on passionflower (Passiflora), and the toxic sap of the vines gives the caterpillar and adult butterfly protection from predators.

This species occurs in the deep South, through Mexico, Central America, and into South America.

The Basics:

  • Does it sting? No
  • What does it eat? Passionflower
  • Will it seriously damage plants or trees? Not usually
  • Is it rare? No, although it is only found in the South
  • What does it turn into? A beautiful black and yellow butterfly
  • Can you raise it to an adult? Yes, if you give it plenty of fresh Passiflora leaves
The caterpillar of the question mark butterfly

The caterpillar of the question mark butterfly

15. The Question Mark

The Question Mark (Polygonia interrogationis) species vaguely resembles the fritillaries but is in a completely separate group, the angle wings. You can tell if a butterfly is an angle wing when they land—they have very irregular wing margins, and the underside is designed to resemble a dead leaf.

This very effective camouflage, combined with the orange upperside, gives the butterfly the ability to seemingly "disappear" when it lands, confusing any hungry birds attempting to follow it. The common name is due to a small metallic silver mark on the underside, which is in the shape of a perfect little question mark.

The very spiny caterpillar of the question mark butterfly is representative of the group. They are all covered with branching spines, which may keep parasitic wasps and flies from being able to land and lay their eggs. The caterpillar eats various kinds of elm, and can often be found in mid-summer on the lower branches of elm trees and saplings, as well as hackberry, nettles, and several other plants.

The Basics:

  • Does it sting? No, although the spines are sharp
  • What does it eat? Elm, hackberry, and nettles
  • Will it seriously damage plants or trees? Not usually
  • Is it rare? No, this species is quite common
  • What does it turn into? A very cool orange butterfly
  • Can you raise it to an adult? Yes, if you give it plenty of fresh leaves

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