By Mary Hoff Wild

S o m e t i m e s Wa n doolly

These creep along, munching on leaves. chubbyinsects

I a bright spring day, perfect for playing catch. But you and your t’s friend are still a little out of practice from the long winter, so you end up in the bushes, looking for an overthrown ball. What is that!? The brightly colored, stumpy-legged creature looks like nothing you’ve ever seen. Welcome to the wild—and sometimes woolly—world of Minnesota caterpillars. A caterpillar is a wormlike called a larva. When fully grown, a caterpillar will turn into a or a butterfly. Caterpillars come in many shapes, sizes, and colors. Some are smooth, fat, and green. Others are hairy, prickly, and brown. Some have spines that look like horns. Others have spots that look like eyes. Some caterpillars live in trees. Others spend their time on flowers. Minnesota is home to at least 800 species of and about 140 butterfly species. That means almost 1,000 different species of caterpillars are creeping, crawling, and munching their way through summer days.

This story introduces a few you might find in your yard or at the park. BILL JOHNSON

44 Minnesota Conservation Volunteer naturalists Y oung ▼

Colorful fleshy knobs, known as tubercles, grow on the body of the cecropia moth caterpillar. Black spikes on the tubercles warn potential May-June 2016 predators to look for an easier meal. 45 Some are smooth spiracles White-lined sphinx moth anatomy (breathing holes) open to take in oxygen and close THORAX ABDOMEN to keep out water 3 segments

horn HEAD

stemmata 4 pairs of stumpy anal prolegs abdominal prolegs mandibles 3 pairs of true (thoracic) legs Final instar can be spinneret up to 3 inches long

3rd instar head anatomy head capsule clypeus (front of face)

stemmata 2nd instar (eyes)

1st instar antenna

mandibles (jaws) spinneret Egg on leaf

Some are hairy Forest tent caterpillar (Malacosoma disstria)

This camouflaged-looper caterpillar glues flower petal bits to its back with silk from its spinneret.

Some decorate themselves The caterpillar of the wavy-lined emerald moth is called a camouflaged-looper caterpillar 2 pairs ( aerata). abdominal prolegs Like every insect, a caterpillar has six true legs. It also Fun has pairs of stumpy parts called prolegs to help grip and Fact crawl. Prolegs have muscles but no hard parts.

Moths and butterflies are that be- frogs, spiders, bears, or other predators. long to a group called Lepidoptera. Look Sometimes wasps, flies, or other insects lay for butterflies during the day when they eggs inside a caterpillar. When those eggs are sipping nectar from blossoms. Most hatch, the young insects, or parasitoids, eat moths are active after dark, but many the caterpillar from the inside. moths are day fliers. You can see hungry If a caterpillar survives long enough, it moth and butterfly caterpillars eating eventually stops eating and gets ready for almost anytime in summer. its next stage of life. It changes into a pupa, Even though different kinds, or species, a new form with hardened, shell-like skin. of caterpillars look very different from By its jaw, a caterpillar has a little nozzle each other, they all share some common called a spinneret. It can force a unique body parts. See if you can find the parts liquid out of its spinneret. The liquid on the next caterpillar you spy. hardens into silk. Some moth caterpillars use silk to make a cocoon. Like a sleeping A Wonderful Life. A caterpillar’s story bag, the cocoon covers the pupal shell. A starts when a female moth or butterfly lays butterfly pupa, usually called a chrysalis, at- a tiny egg, most likely on a leaf or twig. After taches itself to a silk pad by hooks on its rear. a week or two, a little larva hatches from the During its pupal stage, the caterpillar egg. A caterpillar has one job: Eat! Chomp- goes through a change called metamor- ing leaf after leaf with its jawlike mandibles, phosis. Inside the shell, the caterpillar’s it grows astoundingly quickly. In a week or muscles and other tissues break down, dis- two, some caterpillars can gain hundreds of solving into a soupy mix. From this mushy times their hatching weight. caterpillar, tiny “seeds” of adult moth or The different stages of a caterpillar’s life butterfly parts, calledimaginal discs, build are called instars. A newly hatched caterpil- an adult insect with wings. lar is a first instar larva. When it grows too After two weeks, or sometimes longer, big for its skin, the caterpillar splits and sheds an adult moth or butterfly emerges from its skin. Then it’s a second instar larva. Most the pupal shell. It stretches its wings and caterpillars go through four or five instars. flies off to begin its most important job: It’s an eat-and-be-eaten world for cat- Reproduce! The caterpillar-turned-flying- erpillars. Before they get a chance to grow insect mates and lays eggs to make the

ILLUSTRATION BY TAINA LITWAK TAINA BY ILLUSTRATION up, most become juicy tidbits for birds, next generation of caterpillars.

May-June 2016 47 Moth Caterpillars OS BY BILL JOHNSON T PHO

IsabellaTiger Moth Pyrrharctia isabella Also known as a woolly bear, this is one place. A chemical in its hemolymph—the of Minnesota’s best-known caterpillars. insect equivalent of blood—helps keep it Fuzzy and black with a fat orange-brown from freezing to death. band around the middle, it grows to about When spring comes, the woolly bear 2 inches long. Some people think that the warms up and starts eating again. After wider a woolly bear’s brown band, the a few days to weeks, it spins a cocoon. In- milder the winter will be. In reality, the side, it changes to a pupa and then finally band gets wider as the woolly bear grows. an adult moth. The moth emerges in People often spy this caterpillar cross- midsummer. It mates, lays eggs, and dies ing a road, sidewalk, or bike path in the within a few days. The caterpillars that fall as it searches for shelter from the cold. hatch from those eggs might have time to A woolly bear spends winter curled into a become moths that same summer. Their ball in a pile of dead leaves or another cozy offspring then overwinter.

48 Minnesota Conservation Volunteer ForestTentCaterpillar Moth Malacosoma disstria Walking through the woods in May, you oak, and other trees, this caterpillar can might see a tree that seems like it forgot grow to be 2 inches long. to grow some of its leaves. Looking a little Sometimes mistakenly called “army- closer, you might notice that its twigs are worms,” which is a different species, these swarming with hairy black-and-blue cat- caterpillars often gather in “conventions” erpillars. Chomping on leaves, they have of 100 or more on a silk mat attached to almost stripped the tree bare. branches. They make the mat by laying Forest tent caterpillars hatch in early down several layers of silk. spring from egg bundles wrapped About mid-June, the caterpillars stop around branches. At first, a larva is about eating. They make silk cocoons. A week or as long as a grain of rice. Voraciously gob- two later, furry brown moths emerge. They bling tender new leaves of aspen, birch, lay eggs, and the cycle begins again.

May-June 2016 49 Moth Caterpillars WHITE-LINED SPHINX MOTH BY BILL JOHNSON SPHINX MOTH WHITE-LINED

White-LinedSphinx Moth COURTESY OF ROBERT DANA Hyles lineata Also known as a hornworm, this mainly grape and tomato plants, the hornworm green-and-black caterpillar has a horn- can grow to be more than 3 inches long. like spike sticking up from its back near When full-grown, it burrows into the soil its rear end. No one knows for sure how and becomes a pupa. the spike helps the caterpillar. What do An adult sphinx moth emerges from you think? the pupal shell after a couple of weeks. White-lined sphinx moths migrate into With its long tongue, it drinks nectar Minnesota from the southern United from flowers, just as hummingbirds do. States in spring. They mate and lay eggs. When finished drinking, the moth coils Tiny caterpillars hatch from eggs in July. its tongue up neatly below its face. Nibbling leaves of primrose, fireweed, White-lined sphinx moths cannot sur- apple and elm trees, and sometimes vive in Minnesota during winter.

50 Minnesota Conservation Volunteer CECROPIA MOTH BY BILL JOHNSON

CecropiaMoth COURTESY OF ROBERT DANA Hyalophora cecropia One of Minnesota’s biggest caterpil- this caterpillar on a tree or shrub dur- lars (along with the big poplar sphinx, ing summer. Pachysphinx occidentalis), this creepy Because the cecropia moth does not crawler can stretch up to 5 inches long have mouthparts or digestive organs, it when fully grown. When it first hatch- must survive on fat stored up during its es, it has black skin covered with bris- days as a caterpillar. tles. Later it turns yellow, then green This species goes through one genera- with brightly colored knobs. Look for tion each year.

May-June 2016 51 Moth Caterpillars PHOTOS BY BILL JOHNSON PHOTOS

Wavy-LinedEmerald Moth Do you like to dress up? The caterpillar of with its true legs and lifting its body into the wavy-lined emerald moth does. Called the shape of a loop. This motion brings the a camouflaged-looper, it feeds on flowers rearmost prolegs up next to the true legs. and camouflages itself by using silk to stick By letting go with the true legs and stretch- bits of blossoms to its back. The picture ing its head forward, the caterpillar moves above shows how flowers help it hide from along—inch by inch. hungry birds and other predators. Look for the tiny camouflaged-looper It is a smallish member of a group of caterpillar in fields and meadows between caterpillars known as inchworms. An early spring and October. The adult moth inchworm travels by gripping a leaf or twig has green wings with wavy white lines.

Caterpillar Haven Here are some pointers for making a friendly place for Lepidoptera to live. • Plant milkweeds and other Minnesota wildflowers for flying insects to sip nectar from the flowers and lay eggs on the plant. • Leave caterpillars on the plants where you find them. • Do not spray chemicals on plants to kill insects you don’t want because moths and butterflies are insects too and they will die.

52 BY BILL JOHNSON QUESTION MARK BUTTERFLY • Put big rocks in sunny spots for butterfliesMinnesota to warm Conservation up in the morning. Volunteer Butterfly Caterpillars MONARCH BUTTERFLY BY BILL JOHNSON MONARCH BUTTERFLY

MonarchButterfly Danaus plexippus COURTESY OF ROBERT DANA The monarch caterpillar starts life as an A monarch caterpillar has wiggly, long, egg the size of a pencil point. A female black feelers—two close to its head and butterfly lays the egg on the underside two near its rear. These feelers might help of a milkweed leaf. The newly hatched the caterpillar sense the world around itself. larva eats its eggshell, then starts chewing After a week or two of gobbling and leaves. One of nature’s pickiest eaters, this growing, the caterpillar attaches itself to a caterpillar eats only milkweed leaves. The plant or other object. It sheds its skin one leaves contain nasty-tasting chemicals last time and hardens into a bright green that don’t bother monarch caterpillars pupa. About two weeks later, an adult but discourage hungry birds and other butterfly emerges. In the fall, the adults predators from having a larva for lunch. migrate all the way to Mexico.

May-June 2016 53 Butterfly Caterpillars BILL JOHNSON JEFF PIPPEN WhiteAdmiral Butterfly Limenitis arthemis arthemis The white admiral caterpillar looks a lot May in northeastern and central Minne- like a bird dropping. How do you sup- sota. It especially likes forests near lakes, pose that helps it survive? rivers, and wetlands. In late fall, a recently Growing up to 2 inches long, it feeds hatched white admiral caterpillar uses on leaves of trees such as aspen and birch. silk to tie a leaf into a tube, then tucks Start watching for this caterpillar in late itself inside for winter.

Work With Insects Robert Dana works for the Department of Natural Resources as an ecologist, studying relationships between living things and their environment. Robert has been fascinated by insects as long as he can remember. Even before he was old enough to go to school, he raised a caterpillar AMANDA PLAIN, DNR AMANDA and watched it turn into a moth. One day, when tomology at the University of Minnesota, where he was about 4 years old, he found a moth on he learned how caterpillars accomplish their amaz- his windowsill and decided to find out if a moth ing transformation. As an ecologist, he works to could turn back into a caterpillar. He pulled off protect native insects and other creatures that its wings and legs, but he quickly realized he had call Minnesota’s forests, prairies, lakes, and rivers made a bad mistake. home. Robert helped choose caterpillars to include As a young man, Robert earned a degree in en- in this story and shared photos and fun facts. BLACK SWALLOWTAIL BUTTERFLY BY BILL JOHNSON BUTTERFLY SWALLOWTAIL BLACK

BlackSwallowtail Butterfly Papilio polyxenes COURTESY OF ROBERT DANA You can find black swallowtail caterpil- ment of its green body. When threatened, lars in gardens because they love to eat the caterpillar pops a bright orange, foul- plants such as carrots and dill. Also look smelling, antler-shaped body part out of for them eating wild Queen Anne’s lace the first segment behind its head. in fields. Did you know these plants are The caterpillar will grow to be about 2 closely related? These caterpillars know. inches long during the 10 to 30 days before When a black swallowtail caterpillar it becomes a pupa, or chrysalis. Besides hatches from its egg in June, it looks like being hooked to a silk pad on a plant, the a small black-and-white blob—like a bird chrysalis has a silk belt around the middle. dropping. As it grows bigger, this cater- Like a safety belt worn by a pole climber, pillar develops a pair of rings on each seg- it helps keep the chrysalis from falling. nV

Teachers resources Find a Teachers Guide and other resources for this and other Young Naturalists stories at mndnr.gov/young_naturalists. 55