Science

2. METAMORPHOSIS ININSECTSANDITS
TYPES
Contents
 Metamorphosis
 Ametabolous
 Gradual metamorphosis
 Compelete metamorphosis
 Incompelete metamorphosis
 Metamorphosis in insects
 Metamorphosis in Butterfly
 Harmonal control in metamorphosis

3. Metamorphosis
Definiti
on “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

4. TypesOfMetamorphosis
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

5. Ametabolous metamorphosis

6. 2.Gradualmetamorphosis
 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

7. Gradualmetamorphosis

8. 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

9. Compelete metamorphosis
Four stages
Egg
Larva
Pupa
Adult

10. 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

11. 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

12. 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.

13. The
Pupa
• The Caterpillar stops
eating and becomes a
Pupa or chrysalis

14. The Butterfly Stage
The Butterfly
• Hhh
• From the Chrysalis a butterfly
emerges

15. The Life Cycle of a
Butterfly

16. Metamorphosis in
Ladybug

17. 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.

18. 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

19. 20-
hydroxyecdysone
 20-hydroxyecdysone initiates and coordinates each molt and
regulates the changes in gene expression that occur during
metamorphosis.

20. Harmonal Control in Insects