4. METAMORPHOSISIN INSECTS AND ITS
TYPES
Contents
Metamorphosis
Ametabolous
Gradual metamorphosis
Compelete metamorphosis
Incompelete metamorphosis
Metamorphosis in insects
Metamorphosis in Butterfly
Harmonal control in metamorphosis
5. Metamorphosis
Definition
“Metamorphosis is a biological process by
which an animal physically develops after birth or hatching,
involving a conspicuous and relatively abrupt change in
the animal's body structure through cell growth and
differentiation.”
Four Stages
Egg
Larva
Pupa
Adult
6. TypesOf Metamorphosis
1. Ametabolous metamorphosis
• Little or no metamorphosis
• eggs immatures
• same shape as the adults.
• get bigger no distinct rearrangements of body structures .
• Immatures juveniles.
• Changes in form during growth are minor
• all immature stages resemble adults.
Examples
i. Springtail
ii. silverfish
iii. firebrats
8. 2. Gradual metamorphosis
Paurometabola
Immatures are called nymphs.
Change in form is gradual,
obvious changes involving
development of external wing pads
differences in color or markings.
Nymphs and adults generally share the same
habitat
Examples
i. Grasshoppers
ii. crickets
iii. true bugs
10. Complete metamorphosis
• “In complete metamorphosis a larva completely changes its
body plan to become an adult”.
• Holometabolous
• Four stages
i. Egg
ii. Larva
iii. Pupa
iv. Adult
Immatures are called larvae and pupae.
Larvae do not resemble adults.
Wings and other adult features ….an immobile pupal stage
Immatures and adults may or may not share habitats
Immatures are adapted for feeding
adults are adapted for reproduction and dispersal.
Butterflies, moths, beetles, flies, ants, bees and wasps
12. Incomplete metamorphosis
In incomplete metamorphosis, only some parts of the
animal’s body change during metamorphosis. Animals that
only partially change their bodies as they mature are called
“hemimetabolous,”
Three stages
i. Egg
ii. Nymph
iii. Adult
13. Incompletemetamorphosis
Immatures are called naiads.
Immatures do not closely resemble adults
naiads have tracheal gills.
transition to adult form is gradual
Nymphs and adults dwell in different habitats.
Examples
Mayflies ,dragonflies ,damselflies and stoneflies
14. Metamorphosis in butterfly
Butterfly Life Cycle
• The Egg
• A butterfly lays her eggs
on a leaf.
• The Larva
• The egg hatches and out
comes a caterpillar , this is
the larva stage.
15. The Pupa
• The Caterpillar stops
eating and becomes a
Pupa or chrysalis
19. Metamorphosis in insects
Insect molting and metamorphosis are controlled by two
effector hormones: the steroid 20-hydroxyecdysone and the lipid
juvenile hormone (JH)
in immature insects Corpora allata ………….juvnile
hormone
inhibits the genes ,promote development of adult
causing the insect to remain "immature"
The corpora allata shrink during the last larval or
nymphal instar
stop producing juvenile hormone. and causes the
insect to molt into an adult (hemimetabolous) or a
pupa (holometabolous).
approach of sexual maturity
brain neurosecretory cells
brain hormone "reactivates" the corpora allata
• juvenile hormone.
20. Cont..
In adult females , stimulates production of
yolk for the eggs.
In adult males ,stimulates the accessory
glands to produce proteins needed for
seminal fluid and the case of the
spermatophore.
In the absence of normal juvenile hormone
production, the adult remains sexually
sterile