|A caterpillar: The larva form of insects from the Lepidoptera order or butterflies. Caterpillars – the larva form of sawflies are affined to caterpillars (the family group of the Hymenoptera order). Unlike caterpillars, abdominal legs are developed on 2nd and 10th segments of the belly in caterpillars of sawflies.
The head with thick sclerite covers and the rest of the body is mainly soft without large sclerites. Bristles, located strictly in the manner specific to individual families, are developed all over the body. Apart from these primary bristles, a thick cover of secondary bristles is found in the advanced ages of many open-living forms (mostly thick in caterpillars from the moth family (Arctiidae)).
The eyes are represented by individual eyes (4-6 pairs) located on each side of the head. Feelers or antennas are short but trinomial. The upper jaws or mandible are for gnawing. Lower jaws (maxilla) and lower lip (labium) are merged as in the case of many other insects with a complete transformation into a uniform labio-maxillary complex. The salivary glands are altered into silk glands.
Three pairs of peraeopods are developed in the majority of caterpillars (a pair on each of the breast segments) and five pairs of false abdominal legs on the 3rd, 4th and 10th segments of the belly. The abdominal legs have small crochets, located in various Lepidoptera groups differently - in the form of a circle, longitudinal or cross-section rows.
Deviations from the specified leg positioning variant are found in different groups of butterflies. The most popular are the geometrid caterpillars, the majority of which have only two pairs of abdominal legs (on the 6th and 10th segments). As a result, geometrid caterpillars move as though “walking”. In Russian as well as German (German: Spannern) the name occurs due to the similarity in movement of the caterpillar to movements of a person’s hand, measuring the length of a strand. The Latin name of the geometrid family - Geometridae (from the Latinized Greek work “Land Surveyor”) also is given to them in connection with this feature. It is less known that abdominal legs can be reduced on the 3rd and 4th segments of the belly in caterpillars of some nuctuid moths (Noctuidae).
More than five pairs of abdominal legs are found in some caterpillars. Micropterigidae have eight pairs, Megalopygidae - seven (on the 2nd, 7th and on the 10th segment), one of the types of tiny moths-miners (Stigmella from Nepticulidae family) - six (on the 2nd and 7th segments) pairs.
Also, legs (both abdominal as well as peraeopods) can be completely reduced in tiny leaf-miner lepidopterous insects.
The majority of the caterpillars are herbivorous, however, caterpillars eating mushrooms and also vegetative and animal remains, and even though extremely rare, predators, hunting on sedentary preys (basically, on various sucking insects) are found. Quite often, the herbivorous kinds harm agricultural crops (for example, cabbage white butterflies or winter moths) and forest plantations (for example, unpaired silkworm). The kinds which can feed on vegetative and animal remains are capable of damaging food stocks and clothes, especially woolen clothes (for example, many kinds of snout moths and so-called real moths). Predatory caterpillars of some Geometridae can be used for the biological fight against scaled insects.
Caterpillars are day creatures, or rhopalocera, butterflies and also the majority of other large lepidopterous insects live in the open on fodder plants. Caterpillars of many moth type Lepidoptera families conduct a reserved way of life: in soil, litter or sod grasses (frequently in silky threads); inside fodder plants, miner leaves, sprouts and fruits; making various covers, which the caterpillar, creeping, drags behind it (the most popular caterpillars for dragging covers are Psychidae, but dragging the covers is widespread). Very few types of caterpillars live in water eating water plants.
All caterpillars are capable of releasing silk. The majority of the caterpillars use silk for binding them to the substratum while creeping. The caterpillar, creeping along the plant or on soil, constantly leaves behind a thin silk thread path. If it falls from a branch, then it will hang on silk thread. Caterpillars of some moth and pyralid families construct tunnels using silk (silky paths). Everyone who has seen the damage done by the caterpillar moths to fur or woolen products noticed silky paths in the under-fur or on the surface of hairy or knitted items. Psychidae and others use a silk thread as the base for making a portable cover. Caterpillars of ermels and some Notodontidae make silk nests on fodder plants. In some families, for example, in eggars, giant silk moths and present silkworms, the caterpillar makes a silk cocoon before molting to a chrysalid. The cocoons of silkworm and some giant silk moths (for example, ailanthus silkworm) are used as raw materials for manufacturing silk.