Caterpillar

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

As with most common names, the application of the word is arbitrary and the larvae of sawflies commonly are called caterpillars as well.[1][2]

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.

Caterpillars as a rule are voracious feeders and many of them are among the most serious of agricultural 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.

Classification

The geometrids, also known as inchworms or loopers, are so named because of the way they move, appearing to measure the earth (the word geometrid means earth-measurer in Greek); the primary reason for this unusual locomotion is the elimination of nearly all the prolegs except the clasper on the terminal segment.

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 beocelli on the head capsule, and an absence of the upside-down Y-shaped suture on the front of the head.^[5]

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 

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).
• sawfly larvae have an invariably smooth head capsule with no cleavage lines, while lepidopterous caterpillars bear an inverted "Y" or "V" (adfrontal suture).