metamorphosis in insects
TRANSCRIPT
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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