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Caterpillars ( ) are the larva of members of the order Lepidoptera (the Insect comprising butterfly and ).
As with most common names, the application of the word is arbitrary, since the larvae of sawfly (suborder Symphyta) are commonly called caterpillars as well. Both lepidopteran and symphytan larvae have eruciform body shapes.
Caterpillars of most species herbivore (Folivore), but not all; some (about 1%) insectivore, and some are even cannibalistic. Some feed on other animal products. For example, feed on wool, and horn moths feed on the hooves and horns of dead .
Caterpillars are typically voracious feeders and many of them are among the most serious of Agriculture pests. In fact, many moth species are best known in their caterpillar stages because of the damage they cause to fruits and other agricultural produce, whereas the moths are obscure and do no direct harm. Conversely, various species of caterpillar are valued as sources of silk, as human or animal food, or for biological control of pest plants.
The inchworm, or looper caterpillars from the family Geometridae are so named because of the way they move, appearing to measure the earth (the word geometrid means earth-measurer in Greek language);"Geometridae." Merriam-Webster.com. Merriam-Webster, n.d. Web. 19 September 2017. the primary reason for this unusual locomotion is the elimination of nearly all the except the clasper on the terminal segment.
Lepidopteran caterpillars can be differentiated from sawfly larvae by:
Caterpillars have evolved defenses against physical conditions such as cold, hot or dry environmental conditions. Some Arctic species like Gynaephora groenlandica have special basking and aggregation behaviours apart from physiological adaptations to remain in a dormant state.
Plants contain toxins which protect them from herbivores, but some caterpillars have evolved countermeasures which enable them to eat the leaves of such toxic plants. In addition to being unaffected by the poison, the caterpillars it in their body, making them highly toxic to predators. The chemicals are also carried on into the adult stages. These toxic species, such as the cinnabar moth ( Tyria jacobaeae) and monarch ( Danaus plexippus) caterpillars, usually advertise themselves with the danger colors of red, yellow and black, often in bright stripes (see aposematism). Any predator that attempts to eat a caterpillar with an aggressive defense mechanism will learn and avoid future attempts.
Some caterpillars regurgitate acidic digestive juices at attacking enemies. Many Papilionidae larvae produce bad smells from extrudable glands called osmeterium.
Some caterpillars, like early instars of the tomato hornworm and tobacco hornworm, have long "whip-like" organs attached to the ends of their body. The caterpillar wiggles these organs to frighten away flies and predatory wasps. Some caterpillars can evade predators by using a silk line and dropping off from branches when disturbed. Many species thrash about violently when disturbed to scare away potential predators. One species ( Amorpha juglandis) even makes high pitched whistles that can scare away birds.
Some caterpillars are gregarious; large aggregations are believed to help in reducing the levels of parasitization and predation. Clusters amplify the signal of aposematic coloration, and individuals may participate in group regurgitation or displays. Pine processionary ( Thaumetopoea pityocampa) caterpillars often link into a long train to move through trees and over the ground. The head of the lead caterpillar is visible, but the other heads can appear hidden. Forest tent caterpillars cluster during periods of cold weather.
Most caterpillars are solely herbivore. Many are restricted to feeding on one species of plant, while others are polyphagous. Some, including the clothes moth, feed on detritus. Some are predatory, and may prey on other species of caterpillars (e.g. Hawaiian Eupithecia). Others feed on eggs of other insects, aphids, scale insects, or ant larvae. A few are parasitic on cicadas or leaf hoppers (Epipyropidae). Some Hawaiian caterpillars ( Hyposmocoma molluscivora) use silk traps to capture snails.
Many caterpillars are nocturnal. For example, the "cutworms" (of the family Noctuidae) hide at the base of plants during the day and only feed at night. Others, such as spongy moth ( Lymantria dispar) larvae, change their activity patterns depending on density and larval stage, with more diurnal feeding in early instars and high densities.
Plants evolve mechanisms of resistance to being eaten by caterpillars, including the evolution of chemical toxins and physical barriers such as hairs. Incorporating host plant resistance (HPR) through plant breeding is another approach used in reducing the impact of caterpillars on crop plants.
Some caterpillars are used in industry. The silk industry is based on the bombyx mori caterpillar.
Caterpillar hair has also been known to cause keratin-conjunctivitis. The sharp barbs on the end of caterpillar hairs can get lodged in soft tissues and such as the eyes. Once they enter such tissues, they can be difficult to extract, often exacerbating the problem as they migrate across the membrane.
This becomes a particular problem in an indoor setting. The hair easily enter buildings through ventilation systems and accumulate in indoor environments because of their small size, which makes it difficult for them to be vented out. This accumulation increases the risk of human contact in indoor environments.
Caterpillars are a food source in some cultures. For example, in South Africa mopane worms are eaten by the bushmen, and in China silkworms are considered a delicacy.
The role of caterpillars in the life stages of butterflies was badly understood. In 1679 Maria Sibylla Merian published the first volume of The Caterpillars' Marvelous Transformation and Strange Floral Food, which contained 50 illustrations and a description of insects, moths, butterflies and their larvae. (2025). 9781443830676, Cambridge Scholars Publishing. ISBN 9781443830676 An earlier popular publication on moths and butterflies, and their caterpillars, by Jan Goedart had not included eggs in the life stages of European moths and butterflies, because he had believed that caterpillars were generated from water. When Merian published her study of caterpillars it was still widely believed that insects were spontaneously generated. Merian's illustrations supported the findings of Francesco Redi, Marcello Malpighi and Jan Swammerdam. (2025). 9781443830676, Cambridge Scholars Publishing. ISBN 9781443830676
Butterflies were regarded as symbol for the human soul since ancient time, and also in the Christian tradition. Goedart thus located his empirical observations on the transformation of caterpillars into butterflies in the Christian tradition. As such he argued that the metamorphosis from caterpillar into butterfly was a symbol, and even proof, of Christ's resurrection. He argued "that from dead caterpillars emerge living animals; so it is equally true and miraculous, that our dead and rotten corpses will rise from the grave." (2025). 9789047422365, BRILL. ISBN 9789047422365 Swammerdam, who in 1669 had demonstrated that inside a caterpillar the rudiments of the future butterfly's limbs and wings could be discerned, attacked the mystical and religious notion that the caterpillar died and the butterfly subsequently resurrected. (2025). 9789047422365, BRILL. ISBN 9789047422365 As a militant Cartesianism, Swammerdam attacked Goedart as ridiculous, and when publishing his findings he proclaimed "here we witness the digression of those who have tried to prove Resurrection of the Dead from these obviously natural and comprehensible changes within the creature itself." (2025). 9789047422365, BRILL. ISBN 9789047422365
Since then the metamorphoses of the caterpillar into a butterfly has in Western societies been associated with countless human transformations in folktales and literature. There is no process in the physical life of human beings that resembles this metamorphoses, and the symbol of the caterpillar tends to depict a psychic transformation of a human. As such the caterpillar has in the Christian tradition become a metaphor for being "born again".
Lewis Carroll's Alice's Adventures in Wonderland includes the Caterpillar as a character. When Alice comments on the caterpillar's inevitable transformation into a butterfly, the caterpillar champions the position that in spite of changes it is still possible to know something, and that Alice is the same Alice at the beginning and end of a considerable interval.
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