Caterpillars are not separate species, but they are larvae of butterflies and moths

Are caterpillars insects? The answer is yes, but they are an incomplete form of certain insects4. Caterpillars are the larval stage of 180,000 insects belonging to the order Lepidoptera, which includes butterflies and moths. Caterpillars develop to become their winged adult form.

Generally, caterpillars have a cylindrical body shape with a segmented structure. Each body segment typically bears a pair of legs. 

They live on every continent except Antarctica. Some countries known for their diverse caterpillar populations include the United States, Brazil, Australia, India, China, and African and European countries.

They have three pairs of true legs and multiple prolegs

One interesting fact about caterpillars is that they have two types of legs: true legs and prolegs or false legs.

The true legs are the three pairs of jointed legs located on the Caterpillar's thoracic segments closest to its head. These legs are"true" because the Caterpillar retains them into adulthood when it transforms into a butterfly or moth. They use these legs to crawl and walk.

Additionally, on their abdomen, caterpillars possess several pairs of fleshy, unjointed prolegs adorned with tiny hooks called crochets. A caterpillar may have up to five pairs of prolegs, but the number can vary among species. These prolegs firmly grip surfaces as they move about while feeding or resting.

However, caterpillars shed these prolegs as they approach pupation, developing structures needed for metamorphosis into chrysalides or pupae during their transition to adult butterflies or moths.

Additionally, sometimes larvae from the Hymenoptera order - which includes ants, bees, and wasps - get mistaken for caterpillars. However, there are key differences. For example, sawfly larvae superficially resemble caterpillars but have unique features. They sport prolegs on each abdominal segment, unlike caterpillars. Caterpillars have hooks on their prolegs, a feature not found in sawfly larvae.

Some species prefer specific plants

Different caterpillar species have evolved to feed on specific host plants1, a fact often reflected in their common names. For example, the Monarch Butterfly Caterpillar feeds exclusively on a milkweed plant5, while the Swallowtail Caterpillar consumes plants from the Apiaceae (carrot) family.

However, few caterpillar species have evolved to be carnivorous or omnivorous. These caterpillars have adaptations that allow them to eat insects or other small animals. Examples of carnivorous caterpillars include the Harvester Caterpillar, which feeds on aphids, a favorite of the ladybug, and the Lacewing Caterpillar, which preys on small insects.

Caterpillars can sting

Next on our caterpillar facts is their stinging abilities. Stinging caterpillars, like the Puss Caterpillar, Io Moth Caterpillar, and Flannel Moth Caterpillar, possess specialized structures with venomous spines or irritating substances as a defensive adaptation. Found in various regions of North and South America, these caterpillars deliver painful stings when touched, deterring predators and potential threats.

Contact with the venomous spines can cause localized reactions, such as an intense burning sensation, swelling, and redness.

While the stings can be uncomfortable and lead to allergic reactions in some cases, they are generally not life-threatening for humans and subside over time without medical intervention.

However, it is best to avoid handling or touching caterpillars in the wild, especially if unsure of their identification, and exercise caution when exploring natural habitats where other caterpillars may reside.

They have multiple eyes

Did you know that caterpillars have a unique feature called "stemmata" or "ocelli" that function as simple eyes?

These light-sensitive cells differ from the compound eyes found in adult insects on the sides of the Caterpillar's head in pairs. The number of ocelli can vary from species to species, with most having six arranged in three pairs.

However, some caterpillars may have fewer or additional ocelli. Despite their small size, these ocelli play an essential role in helping caterpillars detect changes in light intensity and navigate their environment, especially during low-light conditions.

Silkworm Caterpillars produce silk

Another caterpillar fact that you might be interested in is that silkworm caterpillars can spin silk threads from a particular protein in their salivary glands.

They use this silk to weave a cozy cocoon for protection as they transform into pupae. The silken thread spun by a single silkworm can be up to 900 meters long, over half a mile! Humans have been breeding silkworms for their silk for thousands of years, a practice known as sericulture.

While silk and silk fabric have many uses, including in fashion and medicine, silk production involves boiling the cocoon killing the moth.

Scientists are exploring ways to use silk in medical applications like stitches, artificial skin, and drug delivery systems because our bodies accept silk more quickly than other materials.