meta morphosis in insects and hormonal control of metamorphosis

1. By
IQRA ASLAM

2. Metamorphosis in Insects
The transformation of an immature insect from a larva to a pupa to an adult

3. Types of metamorphosis
• Ametabolous metamorphosis
• Gradual metamorphosis
• Incomplete metamorphosis
• Complete metamorphosis

4. Ametabolous metamorphosis
• (Ametamorphosis )"without metamorphosis
• eggs ……………..immatures
• same shape as the adults.
• get bigger no distinct rearrangements of body
structures .

5. • Immatures ……….juveniles.
• Changes in form during growth are minor
• all immature stages resemble adults.

6. Examples
• Springtails
• silverfish
• firebrats

8. Gradual metamorphosis
• 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.
• grasshoppers ,crickets and true bugs

10. Complete metamorphosis
(Holometabolous)
• Immatures are called larvae and pupae.
• Butterflies, moths, beetles, flies, ants, bees and wasps.
• 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.
• Instar: The insect itself between molts ... "third instar
(larva)"

12. Incomplete metamorphosis
(Hemimetabolous)
• Immatures are called naiads.
• Mayflies ,dragonflies ,damselflies and
stoneflies.
• Immatures do not closely resemble adults
• naiads have tracheal gills.
• transition to adult form is gradual
• Nymphs and adults dwell in different habitats.

14. Hormonal control of metamorphosis
• 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).

15. • approach of sexual maturity
• brain neurosecretory cells
• brain hormone "reactivates" the corpora
allata
• juvenile hormone.
•

16. • 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.

17. Hormonal Control of Insect Metamorphosis
Brain
Temperature,
Light, Stress,
etc.
Corpus Allatum
Juvenile
Hormone (JH)
Larva
Pupa
Adult