Metamorphosis in insects

By

IQRA ASLAM

Metamorphosis in Insects

Metamorphosis in InsectsThe transformation of an immature insect from a larva to a pupa to an adult

Types of metamorphosis

• Ametabolous metamorphosis• Gradual metamorphosis • Incomplete metamorphosis• Complete metamorphosis

Ametabolous metamorphosis

• (Ametamorphosis )"without 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

• Springtails• silverfish• firebrats

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

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)"

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.

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).

• approach of sexual maturity• brain neurosecretory cells • brain hormone "reactivates" the corpora

allata• juvenile hormone. •

• 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.

Hormonal Control of Insect Metamorphosis

BrainTemperature, Light, Stress, etc.

Corpus Allatum

Juvenile Hormone (JH)

LarvaPupa

Adult

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