Entomology 10

Pupal stage of a moth species

Metamorphosis and Molting

  1. Metamorphosis
    1. Exoskeleton
    2. Growth through molting
  2. Types of Metamorphosis
    1. Hemimetabolous - incomplete metamorphosis
      1. Egg to nymph (several molts) to adult
      2. Ex. Cockroaches, grasshoppers, earwigs, termites, aphids, leafhoppers, bugs, lice, etc.
    2. Holometabolous - complete metamorphosis
      1. Egg to larva (several molts) to pupa to adult
      2. Ex. Butterflies, moths, flies, fleas, beetles, bees, wasps, etc.
  3. Molting Process
    1. Apolysis
    2. Epicuticle formed
    3. Procuticle formed
    4. Ecdysis (middorsal ecdysial suture)
    5. Expansion
    6. Hardening and darkening
    7. Endocuticle deposition
  4. Hormones and Metamorphosis
    1. Hormone - a chemical that transmits information from one part of body to another to regulate a physiological process
    2. Neurosecretory cells in brain - production of Prothoraciotropic hormone (PTTH)
    3. Corpus cardiacum (storage of PTTH) (corpora cardiaca pl)
    4. Corpus allatum (juvenile hormone production) (corpora allata pl)
    5. A few examples of insect hormones
      1. Prothoraciotropic hormone (PTTH)
        1. Activates prothoracic gland to produce ecdysone (molting hormone)
        2. Ecdysone initiates molting process
        3. Prothoracic gland degenerates in adults
      2. Eclosion hormone
        1. Controls emergence pattern of adults
        2. Daily rhythm of adult emergence
        3. Produced in neurosecretory cells - stored in corpus cardiacum
      3. Juvenile hormone (JH)
        1. Produced in corpus allatum
        2. Maintains juvenile characteristics (high titer); High JH plus ecdysone molts to next larval instar
        3. Pupal and/or adult characteristics (low titer); Low JH plus ecdysone molts to pupa and/ or adult
        4. In adults, stimulates vitellogenin production
  5. Derivation of scientific words or prefixes
    Apolysis - (Gr. apo, away; lysis, loosen) The first process of molting, characterized by the detachment of the old cuticle from the underlying epidermal cells.
    Chitin - (Gr. chiton, tunic) A linear polysaccharide that resembles cellulose and constitutes one-fourth to one-half of the dry weight of the exo- and endocuticle.
    Corpus allatum - (L. corpus, body; allatum, brought) Endocrine gland that secretes juvenile hormone and stores and releases some brain hormone.
    Corpus cardiacum - (L. corpus, body; Gr. kardia, heart) Neurohemal organ where some brain hormones are stored and released.
    Ecdysis - (Gr. ekdysis, getting out of) Molting, the process of shedding cuticle or exoskeleton.
    Ecdysone - A hormone that initiates the growth and molting activity of the epidermal cells (i.e., ecdysis).
    Eclosion - (F. eclosion, emerge) The act or process of emerging from the egg or pupal case.
    Epicuticle - (Gr. epi, upon; L. cutis, skin) Unpigmented outer layer of the insect cuticle.
    Epidermis - (Gr. epi, upon; derma, skin) The cellular layer of the insect integument.
    Endocuticle - (Gr. endo, within; L. cutis, skin) - the inner, unstabilized layer of the chitinous cuticle that is digested during molting.
    Exo - (Gr. out of)
    Hemimetabolous - (Gr. hemisys, half; metabole, change) Undergo gradual change in form with the nymphs similar in body form to the adults; incomplete metamorphosis.
    Holometabolous - (Gr. holos, whole; metabole, change) Metamorphosis with a larva, pupa and adult; complete metamorphosis.
    Metamorphosis - (Gr. after, change of; morphe, form) A change in form.
    Neuro - (Gr. neuro, nerve)
    Pro - (Gr. pro, before)
    Vitellogenin - (L. vitellus, yolk, gigere, to produce) Protein produced in the fat body that is transferred to oocytes during vitellogenesis.
    Vitellogenesis - Producing yolk.

Suggested Readings: Gullen, P. J. and Cranston, P. S. (1994).
pp. 61-68, Sections 3.2 and 3.3; pp. 160-164, Section 6.3.

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