Insect developmental biology

thumb|Euthalia aconthea (baron butterfly) caterpillar found in India thumb|Caterpillar of Papilio machaon thumb|upright|A monarch butterfly (Danaus plexippus) caterpillar feeding on an unopened seed pod of [[swamp milkweed]]

thumb|250px|Larva of the Papilio xuthus [[butterfly]] thumb|Eurosta solidaginis goldenrod gall fly larva

thumb|upright=1.6|Pupa of the rose chafer beetle, Cetonia aurata thumb|Tumbler (pupa) of a mosquito. Unlike most pupae, tumblers can swim around actively. A pupa (; : pupae) is the life stage of insects from the Holometabola clade undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages thereof being egg, larva, pupa, and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoraci

thumb|upright=.8|Last Moulting|molting of a [[cicada giving rise to the winged imago]]

immature form of insects and some other invertebrates

thumb|Maggots on a porcupine carcass thumb|Maggots feeding on an opossum [[carrion]] thumb|Common wild pig (boar) corpse decomposition timelapse. Maggots are visible. A maggot is the larva of a fly (order Diptera); it is applied in particular to the larvae of Brachycera flies, such as houseflies, cheese flies, hoverflies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and crane flies.

thumb|upright=1.5|Eight locust instars illustrate the gradual change in hemimetabolous insects. Hemimetabolism or hemimetaboly, also called partial metamorphosis and paurometabolism, is the mode of development of certain insects that includes three distinct stages: the egg, nymph, and the adult stage, or imago. These groups go through gradual changes; there is no pupal stage. The nymph often has a thin exoskeleton and resembles the adult stage but lacks wings and functional reproductive organs. The hemimetabolous insects differ from ametabolous taxa in that the one and only adult instar underg

thumb|150px|Lifestages of a holometabolous insect (wasp). Egg is not shown. Third, fourth, and fifth images depict different ages of pupae. Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphic trait of all insects in the clade Holometabola. Immature stages of holometabolous insects are very different from the mature stage. In some species, a holometabolous life cycle minimizes competition between larvae and adults by separating their ecological niches. The m

Ecdysone is a prohormone of the major insect molting hormone 20-hydroxyecdysone, secreted from the prothoracic glands. It is of steroidal structure. Insect molting hormones (ecdysone and its homologues) are generally called ecdysteroids. Ecdysteroids act as moulting hormones of arthropods but also occur in other related phyla where they can play different roles. In Drosophila melanogaster, an increase in ecdysone concentration induces the expression of genes coding for proteins that the larva requires. It causes chromosome puffs (sites of high expression) to form in polytene chromosomes. Recen

thumb|300px|Imperial moth (Eacles imperialis) development from egg to pupa, showing all the different instars

class of chemical compounds

one of the parts of a holometabolous insect larva

Hypermetamorphosis, or heteromorphosis, is a term used mainly in entomology; it refers to a class of variants of holometabolism, that is to say, complete insect metamorphosis. Hypermetamorphosis is exceptional in that some instars, usually larval instars, are functionally and visibly distinct from the rest. The differences between such instars usually reflect transient stages in the life cycle; for instance, one instar might be mobile while it searches for its food supply, while the following instar immediately sheds its locomotory organs and settles down to feed until it is fully grown and re

Ametabolism is a type of growth or life cycle in insects in which there is slight or no metamorphosis, only a gradual increase in size. It is present only in primitive wingless insects: the orders Archaeognatha and Zygentoma.

embryogenesis of the fruit fly Drosophila, a popular model system

heterodimeric complex containing the products of the insect genes Ecdysone receptor (EcR) and ultraspiracle (usp). Binding of ecdysone promotes association between the two subunits, and the receptor complex then initiates molting and metamorphosis