Buzz
While some view caterpillars as cute, charming little beings, others are filled with fear at the sight of them. Yet, most people remain unaware of just how truly fascinating and strange the world of these unassuming creatures can be.
From toxic nicotine breath to 'butt communication,' to an astonishing metamorphosis process, these squishy critters have much more to offer than you'd expect at first glance.
This extraordinary list will unveil mind-boggling feats of control, a surprising new method of movement, ants hypnotized into submission, and even a caterpillar resembling Donald Trump.
10. A Mobile Suit of Armor
A recently discovered species of hermit crab caterpillar from Peru displays a behavior never before observed in caterpillars. This fascinating critter creates its own protective suit of armor, resembling a small, mobile cage made from leaves. It rolls these leaves into a tube and uses its sticky saliva to glue them together. Once inside this leafy shelter, the caterpillar drags itself along the forest floor by pulling the tube behind it with its mouth.
As it searches for food, the caterpillar’s body stays safe, snug inside its portable cocoon. The resourceful insect even leaves a little bulge in the middle of its tube, allowing it to turn around inside if it needs to make a quick escape out the back end.
9. Incredible Camouflage
Caterpillars use all kinds of strange disguises to keep their vulnerable, soft bodies hidden from predators. Some caterpillars mimic bird droppings, others sport markings that look like snake eyes, and a few non-toxic species imitate the patterns of toxic caterpillars to trick would-be predators into staying away.
However, one species stands out from the rest. The camouflaged looper caterpillar is unique in its method of disguise. It decorates its body with petals and other plant pieces it collects from its diet. The caterpillar attaches these bits of plant matter to its back using silk from its own body. When the camouflage begins to fade, the looper sheds its old disguise and starts the process all over again.
8. The Leaping Caterpillar
In the lush forests of Southern Vietnam, one species of caterpillar, known as Calindoea trifascialis, surrounds itself with leaves to create a small, protective sleeping bag as it prepares to pupate. This caterpillar then hops around the forest floor, encased in its leafy cocoon, avoiding sunlight. To propel itself, it anchors its anal prolegs to the bottom of its leafy shelter and uses a piston-like motion to jump, moving away from the direction it’s facing.
The caterpillar hops in this manner for up to three days before settling down to begin its metamorphosis. When Chris Darling first studied this yellow caterpillar in 1998, he and his students noticed it was secreting a strange liquid. In a curious moment, Darling decided to lick the caterpillar to test it. Although it didn’t taste like much, his tongue went numb. This led him to suspect the caterpillar was using a chemical defense. In the lab, Darling discovered that the substance he had licked was a mix of hydrocarbons and hydrogen cyanide, which coats the caterpillar's body. The toxic smell emanating from the caterpillar’s makeshift sleeping bag deters ants and other predators that might otherwise try to feast on it.
7. The Mad Hatterpillar
The gum-leaf skeletoniser caterpillar features a peculiar, fuzzy horn on its head. This odd structure is actually a ‘hat’ made from the old head capsules the caterpillar sheds with each molt. Each time the caterpillar sheds its skin, it places the most recent head capsule on top of its new head, gradually building a small tower of discarded heads.
Each gum-leaf skeletoniser can molt up to thirteen times before its metamorphosis, causing its ‘hat’ to grow taller and taller, eventually towering over its small body. The exact reason for this peculiar behavior remains a mystery, but researchers speculate that the unusual headdress might act as a defense mechanism, tricking predators into attacking the discarded heads rather than the caterpillar itself. While this theory seems reasonable, studies show that when the caterpillar faces off with a deadly predator in the controlled environment of a petri dish, even those with the tallest hats fare no better than their hatless counterparts. Perhaps they simply enjoy creating and wearing hats!
6. The Musical Maestros of the Insect World
One species of caterpillar has developed an impressive form of communication: they converse through their behinds. Researchers at Carlton University in Canada discovered that birch caterpillars have specialized anal ‘oars’ that they drag across leaves to send signals to other caterpillars. This isn't their only method of communication—these caterpillars also shake their bodies and drum their mandibles against leaf blades to create a variety of signals within their group. As one caterpillar begins drumming, shaking, and scraping, others are drawn to the noise, forming small clusters.
While scientists haven’t fully deciphered what each signal means and some debate whether the caterpillars are truly communicating, evolutionary biologist Jayne Yack states, “I have been studying insect sounds for more than 30 years, and I’ve never seen an insect species produce such a diversity of signal types.” This discovery provides the first evidence that caterpillars may rely on vibrations to form social groups.
5. Toxic Nicotine Breath
One of the tobacco hornworm’s preferred meals is the highly toxic foliage of the tobacco plant. The tobacco plant produces nicotine, a deadly poison that serves as a defense mechanism to protect itself from animals that might try to eat it. Remarkably, the tobacco hornworm not only consumes nicotine in quantities that would kill any other creature, but it also possesses a unique gene that allows it to use the nicotine toxins as its own defense system.
The caterpillar absorbs the nicotine into its hemolymph, the insect equivalent of blood. It then opens small pores in its skin, called spiracles, releasing toxic miasmic clouds of poison into the air. This defense mechanism is known as defensive halitosis (meaning bad breath as a defense). When the caterpillar expels these toxic clouds at predators like the wolf spider, it helps ward them off and prevents the caterpillar from being eaten.
4. Hawaii’s Carnivorous Caterpillars
Hawaii is home to several carnivorous caterpillars that lie in wait for unsuspecting prey. One such species, Hyposmocoma molluscivora, refuses to eat plants, even when starving. This tiny caterpillar, measuring only about eight millimeters long, prefers to hunt snails, ambushing and slowly devouring them alive. To keep its prey from escaping, Hyposmocoma molluscivora attaches its snail victim to a leaf using silk, much like a spider cocoons its prey. The caterpillar then crawls into the snail’s shell and traps it, eating the snail alive until only an empty shell remains.
Though Hyposmocoma molluscivora is the only known species of caterpillar that feeds on snails, it holds another remarkable distinction: it is the first fully amphibious insect discovered. This caterpillar can survive just as easily underwater as it can on land, though scientists remain puzzled by how it breathes when submerged. Daniel Rubinoff, from the University of Hawaii, speculates that the caterpillar might have an undiscovered specialized breathing organ or oxygen-diffusing pores in its skin.
Another carnivorous caterpillar species from Hawaii, Eupithecia, resembles a small clawed hand, poised to strike unsuspecting prey. These masters of disguise stretch their bodies alongside leaves, mimicking a harmless stick, until an unsuspecting victim wanders by. In the blink of an eye, Eupithecia snaps its body downward, seizing its prey with its long, claw-like legs before devouring its undoubtedly startled meal. Hawaii is home to 18 different species of carnivorous caterpillar.
3. Caterpillar Soup and Imaginal Disks
Most people know that caterpillars spin cocoons to protect their chrysalis as they undergo metamorphosis. The chrysalis itself grows underneath the caterpillar’s last skin layer, and once the caterpillar sheds its skin, the chrysalis is revealed. Initially soft, the chrysalis hardens to protect the caterpillar inside during its pupation. Here’s where it gets truly bizarre: After encasing itself in the protective shell, the caterpillar releases digestive enzymes that turn its body into a soupy mush. The caterpillar literally dissolves itself, leaving behind important structures known as imaginal disks.
So, what exactly are imaginal disks? To answer that, we must go back to the caterpillar’s earliest stages, when it was still a tiny egg. As it grows, the caterpillar forms clusters of cells inside its body called imaginal disks. Each disk corresponds to a part of the adult moth or butterfly it will become; there are disks for the wings, eyes, antennae, and so on.
Once the caterpillar has liquefied most of its body, leaving only the imaginal disks floating in a liquid soup, these disks use the surrounding goop as fuel for rapid cell division. This allows them to transform into the adult butterfly or moth. The entire process of transformation, from egg to larvae to adult, is known as holometabolism.
It may seem hard to believe, but scientists later found that certain species of moths can actually retain memories from their days as caterpillars. Evolutionary ecologist Martha Weiss conducted an experiment in which tobacco hornworm caterpillars were placed in a Y-shaped tube. One path led to an area filled with the smell of ethyl acetate, while the other led to clean air. The caterpillars that chose the ethyl acetate side were shocked, and 78% of them avoided the chemical’s smell afterward. A month later, after they had undergone metamorphosis, the adult moths were tested again. Remarkably, 77% of them still avoided the ethyl acetate, which, according to Weiss, suggests that “parts of the brain are retained that allow memories to persist through this very dramatic transition.”
+Every Caterpillar’s Worst Nightmare
Glyptapanteles is a name that strikes fear into the heart of any caterpillar. This Brazilian parasitoid wasp species subjects caterpillars to horrifying experiences that make us thankful we aren’t caterpillars living in Brazil. The female Glyptapanteles first inserts her egg-filled stinger into the body of Thyrinteina leucocerae, a harmless caterpillar that’s happily munching on leaves. The eggs hatch and the larvae begin feeding on the caterpillar’s insides while it continues with its everyday activities. The caterpillar even sheds multiple skins as the larvae slowly consume it from the inside out.
After the larvae have consumed most of the caterpillar’s insides, they burrow through its skin and spin themselves cocoons to mature into adult wasps. You might expect the caterpillar to die at this point, but strangely, it continues to protect the larvae with what little remains of its life. The caterpillar stops eating, ceases moving, and even wraps itself around the pupating wasps. It will aggressively thrash around to protect them from any nearby insects. When the adult wasps finally emerge, the caterpillar dies.
Though scientists don’t fully understand why the caterpillar behaves so strangely after its invaders leave its body, they discovered that some larvae remain inside the caterpillar after the others have burrowed out to pupate. Researchers speculate that these remaining larvae might somehow influence the caterpillar’s behavior, possibly sacrificing themselves for the benefit of their kin. This theory, however, still requires further investigation.
2. Free-Floating Guts and Soft-Bodied Robots
Many people are familiar with the way caterpillars crawl in a smooth, undulating motion, but what happens inside their bodies during this movement is entirely unique: their guts move almost a full step ahead of the rest of their body. This intriguing discovery was made by biologists at Tufts University of Arts and Sciences when they x-rayed tobacco hornworm caterpillars to understand their movement mechanics.
X-raying a caterpillar is no simple task because, unlike other animals, caterpillars have no bones. To overcome this challenge, biologist Michael Simon and his team placed their subjects on a custom-built caterpillar treadmill and examined their insides using a special x-ray device powered by a particle accelerator at Argonne National Laboratory in Illinois. What they found was that the caterpillar’s guts move independently, advancing ahead of the body and legs. Simon, the lead author of the study published in Current Biology, explained, 'Although internal tissue movement caused by locomotion has been identified in many organisms, the caterpillars seemed to be propelling themselves forward by means of a two-body system—the body wall container and the gut it contained. This may contribute to the extraordinary freedom of movement seen in these soft-bodied crawlers.' This novel locomotion has been termed visceral locomotive pistoning.
You might wonder why it’s important to understand what happens to a caterpillar’s guts as it moves, but these findings are actually helping shape the design of soft-bodied robots that could be used for transportation. In July 2010, Michael Simon explained to LiveScience, 'One of the big advantages of a soft robot is the ability to move cargo, such as electronics, tools, or chemicals. A robot with a skeleton has a fixed structure, but a soft-bodied robot can deform, both to the outside environment and to the interior contents.'
'There are still opportunities for discovery even in the most humble of places,' Simon remarked, reflecting on the insights his team gained about how caterpillars move.
1. Caterpillar Overlords
The caterpillars of Japan's oakblue butterfly possess a remarkable defense strategy against predators like spiders, wasps, and other insects: they enslave ants and turn them into aggressive bodyguards. The caterpillar does this by secreting a sweet, sugary liquid through its skin, which attracts ants. Once the ants consume this secretion, they become fixated on the caterpillar and abandon their nests, food sources, or any other activities, staying loyal to their new overlord.
In addition to this unusual tactic, the caterpillar can issue an attack command by flipping its tentacles (the small stalks atop its head). This causes the ants to become highly aggressive and attack any nearby threats. Masuru Hojo of Kobe University in Japan speculates that glands near the caterpillar’s tentacles might secrete chemicals that trigger the ants' aggression. Hojo suggests, 'It is possible that both visual and chemical signals are stimulating the ant aggression.' Ants that have not ingested the sugary droplets do not respond to the caterpillar’s command, leading Hojo to believe the secretion contains a chemical that influences the ants' behavior after consumption.
++Trumpapillar
This fuzzy creature, known as the flannel moth caterpillar, earned the nickname 'Trumpapillar' from researchers who encountered it in the Peruvian Amazon, due to its striking resemblance in both color and texture to Donald Trump’s hair. While these caterpillars can appear in various colors such as white, pink, red, and yellow, the 'Trumpapillar' name stuck because of its distinctive, hair-like appearance.
The caterpillar’s body is covered with hairs that closely resemble those of a tarantula, and these hairs are equipped with tiny venomous spines that cause an intense rash upon contact. This defense mechanism is so effective that, in a classic example of Batesian mimicry, the chicks of the cinereous mourner, an Amazonian bird, closely resemble the fuzzy yellow caterpillar. When threatened, the baby bird mimics the caterpillar’s movements exactly, deterring predators such as snakes and monkeys that seek to avoid the venomous Trumpapillar at all costs.
