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INSECTS II

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Complete metamorphosis: an insect progresses through several distinct stages: ... O. Orkin Insect Zoo. http://insectzoo.msstate.edu ... – PowerPoint PPT presentation

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Title: INSECTS II


1
INSECTS II
What stages of life do insects go through? How do
caterpillars relate to butterflies? Larvae,
Nymphs Adults Exoskeletons
2
Stages of Life
  • Incomplete metamorphosis an egg becomes a
    nymph, which evolves gradually into an adult.
  • Complete metamorphosis an insect progresses
    through several distinct stages egg to larva to
    pupa to adult.

3
Incomplete metamorphosis
Nymphs and adults eat the same food and live
in the same surroundings.
4
Complete Metamorphosis
Larvae and adults may eat different foods, thus
avoiding competition for a single resource.
5
The Life Cycle of a Butterfly
  • The first stage is called the egg stage. The
    mother butterfly lays eggs on a leaf.
  • In the larva (2cd) stage, the egg hatches on the
    leaf and out comes a caterpillar.
  • In the pupa (3rd) stage the caterpillar grows and
    it pops out of its old skin, already wearing a
    new one.
  • The adult (4th) stage is also called the Imago.
  • The Imago (5th) stage begins when the chrysalis
    is broken and the butterfly breaks out.

6
The Larva Stage
  • The caterpillar grows and it pops out of its old
    skin, already wearing a new one four or five
    times, after which the caterpillar begins to
    produce silk. With this silk, it attaches its
    body to a leaf or twig. It then sheds its furry
    skin for the last time. Under the skin is a hard
    form called chrysalis. The caterpillar's body
    turns to a soft liquid, from which the wings,
    legs and other body parts of the butterfly will
    form.

7
Exoskeletons I
  • An insect's exoskeleton serves as a
  • protective covering over the body
  • a surface for muscle attachment
  • a water-tight barrier against desiccation
  • sensory interface with the environment

8
Exoskeletons II
  • Composed of overlapping, hardened plates, with
    membranous areas between the plates, for maximum
    strength with flexibility
  • Good at reducing water loss to the environment,
    which is critical for a small organism with a
    large surface area to volume ratio

9
Exoskeletons III
  • The exoskeleton is composed of chitin surrounded
    by a matrix of protein that varies in composition
    from insect to insect
  • Our fingernails are composed of chitinthe same
    material in an insects exoskeleton!

10
Molting I
11
Molting II
  • The destruction of old cuticle, formation of new
    and larger cuticle, and shedding of remnants of
    old cuticle.
  • Old cuticle is partially used to make new one.
  • Newly molted insect appears whitish, since no
    color in cuticle. They are NOT albinos.
  • New cuticle tans (like a hide), hardens, and
    takes color in short time.

12
Molting II continued..
13
Controls of Molting
  • Controlled by endocrine system, and by brain.
  • Gut receptors, elsewhere indicate stretching.
  • Cells in brain secrete hormone that stimulates
    prothoracic gland. This gland produces a molting
    hormone called ecdysone.
  • Molting controlled by brain and prothoracic gland
    in prothorax.

14
Sources
  • 1. Insects and Human Society
  • http//www.ento.vt.edu/ihs/distance/lectures/abun
    dance/abundance_slide04.shtml
  • O. Orkin Insect Zoo
  • http//insectzoo.msstate.edu
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