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Metamorphosis in insects

There are three main types of metamorphosis in insects: ametabolous, gradual (incomplete), and complete. Ametabolous insects like springtails undergo simple growth without morphological changes between immature and adult stages. Gradually metamorphosing insects like grasshoppers change gradually through nymph stages that resemble adults. Completely metamorphosing insects like butterflies undergo a dramatic transformation through distinct larva and pupa stages before emerging as adults. The production and cessation of juvenile hormone by the corpora allata gland controls whether an insect remains immature or undergoes metamorphosis into an adult form.

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By IQRA ASLAM
Metamorphosis in Insects The 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 Brain Temperature, Light, Stress, etc. Corpus Allatum Juvenile Hormone (JH) Larva Pupa Adult
Metamorphosis in insects