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For other uses, see Caterpillar (disambiguation).
Caterpillar of Papilio machaon
A monarch butterfly (Danaus plexippus) caterpillar feeding on a leaf of the swamp milkweed (Asclepias incarnata) in a private garden in Lancaster, Pennsylvania.

Caterpillar /ˈkætərˌpɪlər/ is the common name for the larvae of members of the order Lepidoptera (the insect order comprising butterflies and moths).


Caterpillars of most species are herbivorous, but not all; some are insectivorous, even cannibalistic. Some feed on other animal products; for example clothes moths feed on wool, and horn moths feed on the hooves and horns of dead ungulates.





A geometrid caterpillar or inchworm
Crochets on a caterpillar's prolegs


Caterpillars have soft bodies that can grow rapidly between moults. Only the head capsule is hardened. The mandibles are tough and sharp for chewing leaves (this contrasts with most adult Lepidoptera, which have highly reduced or soft mandibles). Behind the mandibles of the caterpillar are the spinnerets, for manipulating silk. Antennae are present on either side of the labrum, but small and relatively inconspicuous.[4]

Some larvae of the Hymenoptera order (ants, bees and wasps) can appear like the caterpillars of the Lepidoptera. Such larvae are mainly seen in the sawfly family. However while these larvae superficially resemble caterpillars, they can be distinguished by the presence of prolegs on every abdominal segment, an absence of crochets or hooks on the prolegs (these are present on lepidopteran caterpillars), prominent ocelli on the head capsule, and an absence of the upside-down Y-shaped suture on the front of the head.[5]

Caterpillars can be confused with the larvae of sawflies (see image on right). Lepidopteran larvae can be differentiated by:

  • the numbers of pairs of pro-legs; sawfly larvae have 6 while caterpillars have up to 5 pairs.
  • the number of stemmata (simple eyes); the sawfly larvae have only two, while a caterpillar has six.
  • the presence of crochets on the prolegs; these are absent in the Symphyta (sawflies).


Many animals feed on caterpillars as they are rich in protein. As a result, caterpillars have evolved various means of defense. The appearance of a caterpillar can often repel a predator: its markings and certain body parts can make it seem poisonous, or bigger in size and thus threatening, or non-edible. Some types of caterpillars are indeed poisonous.

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[6] apart from physiological adaptations to remain in a dormant state.[7]



Many caterpillars are cryptically colored and resemble the plants on which they feed. They may even have parts that mimic plant parts such as thorns. Their size varies from as little as 1 mm to about 75 millimetres (3.0 in). Some look like objects in the environment such as bird droppings. Many feed enclosed inside silk galleries, rolled leaves or by mining between the leaf surfaces. Caterpillars of Nemoria arizonaria that grow in spring feed on oak catkins and appear green. The summer brood appear like oak twigs. The differential development is linked to the tannin content in the diet.[8]

Chemical defenses[edit]

More aggressive self-defense measures are taken by some caterpillars. These measures include having spiny bristles or long fine hair-like setae with detachable tips that will irritate by lodging in the skin or mucous membranes.[5] However some birds (such as cuckoos) will swallow even the hairiest of caterpillars. Other caterpillars acquire toxins from their host plants that render them unpalatable to most of their predators. For instance, ornate moth caterpillars utilize pyrrolizidine alkaloids that they obtain from their food plants to deter predators.[9] The most aggressive caterpillar defenses are bristles associated with venom glands. These bristles are called urticating hairs. A venom which is among the most potent defensive chemicals in any animal is produced by the South American silk moth genus Lonomia. Its venom is an anticoagulant powerful enough to cause a human to hemorrhage to death (See Lonomiasis).[10] This chemical is being investigated for potential medical applications. Most urticating hairs range in effect from mild irritation to dermatitis.

Giant swallowtail caterpillar everting its osmeterium in defense



Defensive behaviors[edit]

Some caterpillars, like 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.[11] 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.[12] Pine processionary (Thaumetopoea pityocampa) caterpillars often link into a long train, moving through trees or over the ground like a snake.[citation needed] The head of the lead caterpillar is visible, but all other heads are hidden.

Eight caterpillars linked together into a train; the head of the lead caterpillar is visible, but the other seven heads are hidden.

Use of other insects[edit]


Some caterpillars are gregarious; large aggregations are believed to help in reducing the levels of parasitization and predation.[14] Clusters amplify the signal of aposematic coloration, and individuals may participate in group regurgitation or displays.


The caterpillar suffers predation from a number of species. The European pied flycatcher is one species that preys upon caterpillars. The flycatcher typically finds caterpillars amongst oak foliage. Paper wasps, like Polistes metrics, Polistes apachus, and Polistes instabilis', also catch caterpillars to feed their young and themselves. Green and brown caterpillars are the most common prey for Polybia sericea.


A pasture day moth caterpillar feeding on capeweed


A gypsy moth caterpillar

Most caterpillars are solely herbivorous. Many are restricted to one species of plant, while others are polyphagous. A few, including the clothes moth, feed on detritus. Most predatory caterpillars feed on eggs of other insects, aphids, scale insects, or ant larvae. Some are predatory, and others prey on caterpillars of other species (e.g. Hawaiian Eupithecia). A few are parasitic on cicadas or leaf hoppers.[17] Some Hawaiian caterpillars (Hyposmocoma molluscivora) use silk traps to capture snails.[18]

Many caterpillars are nocturnal. For example, the "cutworms" (of the Noctuidae family) hide at the base of plants during the day and only feed at night.[19] Others, such as gypsy moth (Lymantria dispar) larvae, change their activity patterns depending on density and larval stage, with more diurnal feeding in early instars and high densities.[20]

Economic effects[edit]




Human health[edit]


Caterpillar hair can be a cause of human health problems. Caterpillar hairs sometimes have venoms in them and species from approximately 12 families of moths or butterflies worldwide can inflict serious human injuries ranging from urticarial dermatitis and atopic asthma to osteochondritis, consumption coagulopathy, renal failure, and intracerebral hemorrhage.[23] Skin rashes are the most common, but there have been fatalities.[24] Lonomia is a frequent cause of envenomation in Brazil, with 354 cases reported between 1989 and 2005. Lethality ranging up to 20% with death caused most often by intracranial hemorrhage.[25]




In popular culture[edit]

Caterpillars have been used symbolically in media to symbolize characters' positioning at or reluctance to progress past an early stage of development (e.g., in the Mad Men season 3 episode, "The Fog", in which Betty Draper has a drug-induced dream, while in labor, that she captures a caterpillar and holds it firmly in her hand[28]) or in combination with butterflies to show their maturation (e.g., in The Sopranos season 5 episode, "The Test Dream", in which Tony Soprano dreams that Ralph Cifaretto has a caterpillar on his bald head that changes into a butterfly).


See also[edit]


  4. ^ "Caterpillar Head Anatomy". 
  6. ^ Kukal, O.; B. Heinrich & J. G. Duman (1988). "Behavioral thermoregulation in the freeze-tolerant arctic caterpillar, Gynaeophora groenlandica". J. Exper. Biol. 138 (1): 181–193. 
  7. ^ Bennett, V. A. Lee, R. E. Nauman, L. S. Kukal, O. (2003). "Selection of overwintering microhabitats used by the arctic woollybear caterpillar, Gynaephora groenlandica" (PDF). Cryo Letters. 24 (3): 191–200. PMID 12908029. 
  8. ^ Greene, E (1989). "A Diet-Induced Developmental Polymorphism in a Caterpillar". Science. 243 (4891): 643–646. Bibcode:1989Sci...243..643G. doi:10.1126/science.243.4891.643. PMID 17834231. 
  10. ^ Malaque, Ceila M. S., Lúcia Andrade, Geraldine Madalosso, Sandra Tomy, Flávio L. Tavares, And Antonio C. Seguro.; Andrade; Madalosso; Tomy; Tavares; Seguro (2006). "A case of hemolysis resulting from contact with a Lonomia caterpillar in southern Brazil". Am. J. Trop. Med. Hyg. 74 (5): 807–809. PMID 16687684. 
  14. ^ Entry, Grant L. G., Lee A. Dyer.; Dyer (2002). "On the Conditional Nature Of Neotropical Caterpillar Defenses against their Natural Enemies". Ecology. 83 (11): 3108–3119. doi:10.1890/0012-9658(2002)083[3108:OTCNON]2.0.CO;2. JSTOR 3071846. 
  15. ^ Monarch Butterfly. Retrieved on 2012-08-14.
  17. ^ Pierce, N.E. (1995). "Predatory and parasitic Lepidoptera: Carnivores living on plants" (PDF). Journal of the Lepidopterist's Society. 49 (4): 412–453. 
  19. ^ "Caterpillars of Pacific Northwest Forests and Woodlands". USGS. 
  21. ^ Tent Caterpillars and Gypsy Moths. Retrieved on 2012-08-14.
  25. ^ Kowacs, PA; Cardoso, J; Entres, M; Novak, EM; Werneck, LC (December 2006). "Fatal intracerebral hemorrhage secondary to Lonomia obliqua caterpillar envenoming: case report". Arquivos de neuro-psiquiatria. 64 (4): 1030–2. doi:10.1590/S0004-282X2006000600029. PMID 17221019. 
  27. ^ Balit, C. R.; Ptolemy, H. C.; Geary, M. J.; Russell, R. C.; Isbister, G. K. (2001). "Outbreak of caterpillar dermatitis caused by airborne hairs of the mistletoe browntail moth (Euproctis edwardsi)". The Medical journal of Australia. 175 (11–12): 641–3. ISSN 0025-729X. PMID 11837874. 
  28. ^ What's Alan Watching?: Mad Men, "The Fog"

External links[edit]