Hormonal Control
Insect growth and metamorphosis are controlled by hormones synthesized by endocrine glands near the front of the body.
Neurosecretory cells in an insect's brain secrete a hormone, the prothoracicotropic hormone (PTTH) that activates prothoracic glands, which secrete a second hormone, usually Ecdysone (a ecdysteroid), that induces ecdysis.
PTTH also stimulates the corpora allata, a retrocerebral organ, to produce juvenile hormone (JH), which prevents the development of adult characteristics during ecdysis. In holometabolous insects, molts between larval instars have a high level of JH, the moult to the pupal stage has a low level of JH, and the final, or imaginal, molt has no JH present at all.
Read more about this topic: Metamorphosing, Insect Metamorphosis
Famous quotes containing the words hormonal and/or control:
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—Robert Musil (1880–1942)
““Have we any control over being born?,” my friend asked in despair. “No, the job is done for us while we’re sleeping, so to speak, and when we wake up everything is all set. We merely appear, like an ornate celebrity wheeled out in a wheelchair.” “I don’t remember,” my friend claimed. “No need to,” I said: “what need have us free-loaders for any special alertness? We’re done for.””
—Marvin Cohen, U.S. author and humorist. The Self-Devoted Friend, New Directions (1967)