In insects, juvenile hormone (also neotenin) refers to a group of hormones which ensure growth of the larva, while preventing metamorphosis. It is secreted by a pair of endocrine glands behind the brain called the corpora allata. Juvenile hormone is also important for the production of eggs in female insects. Most insect species contain only juvenile hormone (JH) III. To date JH 0, JH I, and JH II have been identified only in the Lepidoptera (butterflies and moths). The form JHB3 (JH III bisepoxide) appears to be the most important JH in the Diptera, or flies. Certain species of crustaceans have been shown to produce and secrete methyl farnesoate, which is juvenile hormone III lacking the epoxide group. Methyl farnesoate is believed to play a role similar to that of JH in crustaceans. Orders See taxonomy Insects are invertebrates that are taxonomically referred to as the class Insecta. ... A hormone (from Greek horman - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... A Pieris rapae larva An older Pieris rapae larva A Pieris rapae pupa A Pieris rapae adult Metamorphosis is a process in biology by which an individual physically develops after birth or hatching, and involves significant change in form as well as growth and differentiation. ... Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. ... An endocrine gland is one of a set of internal organs involved in the secretion of hormones into the blood. ... In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... Super Families Butterflies Hesperioidea Papilionoidea Moths Micropterigoidea Heterobathmioidea Eriocranioidea Acanthopteroctetoidea Lophocoronoidea Neopseustoidea Mnesarchaeoidea Hepialoidea Nepticuloidea Incurvarioidea Palaephatoidea Tischeriodea Simaethistoidea Tineoidea Gracillarioidea Yponomeutoidea Gelechioidea Zygaenoidea Sesioidea Cossoidea Tortricoidea Choreutoida Urodoidea Galacticoidea Schreckensteinioidea Epermenioidea Pterophoroidea Aluctoidea Immoidea Axioidea Hyblaeoidea Thyridoidea Whalleyanoidea Pyraloidea Mimallonoidea Lasiocampoidea Geometroidea Drepanoidea Bombycoidea Calliduloidae Hedyloidea Noctuoidea Families About... Suborders Nematocera (includes Eudiptera) Brachycera Diptera (di - two, ptera - wings), or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. ... Classes Remipedia Cephalocarida Branchiopoda Ostracoda Maxillopoda Malacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum. ...

Control of development

The titre of JH found in the haemolymph of the developing insect controls the stage of development that the insect is in. During ecdysis the form of the new cuticle laid down before the next moult is controlled by the JH level in the insect. JH maintains a juvenile state, and so the level of it gradually decreases during the development of the insect, allowing it to proceed to successive instars with each moult. Hemolymph (or haemolymph) is the blood analogue used by those animals, such as all arthropods and most mollusks, that have an open circulatory system. ... Ecdysis is the molting of the cuticula in arthropods and related groups (Ecdysozoa). ... An instar is a developmental stage of arthropods, such as insects, between each molt. ...

This has been demonstrated in various studies, most prominently that by V. B. Wigglesworth. In this two adult Rhodnius had their blood systems linked, ensuring that the JH titre in both would be equal. One was a third instar Rhodnius, the other was a fourth instar. When the corpora allata of the third instar insect were removed, the level of JH was equal in both insects to that in the fourth instar animal, and hence both proceeded to the fifth instar at the next moult. When the fourth instar Rhodnius had its corpora allata removed, both contained a third instar level of JH and hence one proceeded to instar four, and the other remained at this instar. The Genus Rhodnius Stal, 1859 belongs to the subfamily Triatominae. ...

Generally, the removal of the corpora allata from juveniles will result in a diminutive adult at the next moult. Implantation of corpora allata into last larval instars will boost JH levels and hence produce a supernumary (extra) juvenile instar. A diminutive is a formation of a word used to convey a slight degree of the root meaning, smallness of the object named, encapsulation, intimacy, or endearment. ...

Use as an insecticide

Synthetic analogues of the juvenile hormone are used as an insecticide, preventing the larvae from developing into adult insects. At high levels of JH, larva can still molt, but the result will only be a bigger larva, not an adult. Thus the reproductive cycle is broken. One insecticide, methoprene, is approved by WHO for use in drinking water cisterns to control mosquito larvae. An insecticide is a pesticide used against insects in all developmental forms. ... Methoprene is a general use insecticide that acts as a growth regulator. ...

Forms

• Juvenile hormone 0
  • CAS methyl (2E,6E)-10R,11S-(oxiranyl)-3,7-diethyl-11-methyl-2,6-tridecadienoate
  • Formula: C₁₉H₃₂O₃
• Juvenile hormone I
  • CAS methyl (2E,6E)-10R,11S-(oxiranyl)-7-ethyl-3,11-dimethyl-2,6-tridecadienoate
  • Formula: C₁₈H₃₀O₃
• Juvenile hormone II
  • CAS methyl (2E,6E)-10R,11S-(oxiranyl)-3,7,11-trimethyl-2,6-tridecadienoate
  • Formula: C₁₇H₂₈O₃
• Juvenile hormone III
  • CAS methyl (2E,6E)-10R-(oxiranyl)-3,7,11-trimethyl-2,6-dodecadienoate
  • Formula: C₁₆H₂₆O₃
• Juvenile hormone JHB3
  • CAS methyl (2E,6E)-6S,7S,10R-(dioxiranyl)-3,7,11-trimethyl-2,6-dodecadienoate
  • Formula: C₁₆H₂₆O₄
• Methyl farnesoate
  • CAS methyl (2E,6E)-3,7,11-trimethyl-2,6-dodecadienoate
  • Formula: C₁₆H₂₆O₂

Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ... Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ... Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ... Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ... Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ... Chemical Abstracts Service (CAS) is a division of the American Chemical Society which produces the Chemical Abstracts, an index of the scientific literature in chemistry and related fields. ...

References

• Wigglesworth, VB. (1964) The hormonal regulation of growth and reproduction in insects. Adv. Insect Physiol. 2: 247-336
• Wigglesworth, VB. (1939) The Principles of Insect Physiology. Cambridge Univ. Press. Cambridge.
• Laufer, H, Borst, D, Baker, FC, Carasco, C, Sinkus, M, Reuter, CC, Tsai, LW, and Schooley, DA. (1987) Identification of a juvenile hormone-like compound in a crustacean. Science 235: 202-205.