Insect metamorphosis























                 METAMORPHOSIS IN INSECTS

Metamorphosis : Metamorphosis (meta = change; morph =  form) is the cyclic and sequential developmental process occurring in the form of an insect from hatching (eclosion) to adult (imago) stage. It involves growth and development. Growth is increase in size of the body as a whole but development implies differential growth.
Stadium: The time between two consecutive ecdyses.
Instar: The age and form of insects during a particular stadium.

Types of metamorphosis

Ametabola : (Apterigotes: eg. Silverfish)
There is no distinct external change in the form of insects during its life cycle, except in size. Young ones or juviniles resemble like the adults.Both the juvenile and adults will undergo several moultings. The juvenile and adult occupies same habitate and have similar feeding habits. In protura, during each moult in the juvenile stage, in addition of abdominal segments anterior to the telson is witnessed and this is termed as anamorphosis.

Metabola: In this type, there are distinct changes in growth, development, habit, habitat in the life stages of insects.

  1. Incomplete metamorphosis: these insects undergo simple metamorphosis, the immature stages lack fully developed wings and genitalia and there is no inactive pupal stage. The wings or wing buds develop externally (exopterygotes).
  1. Paurometabola. Eg. Grass hoppers, plant bugs.
    • Thisis simple type of metamorphosis
    • The immature stages are called nymphs that resemble the adults except in size. They lack fully developed wings and genitalia.
    • Both the nymphs and adults present in same habitat and have similar feeding habits.
  2. Hemimetabola. Eg: Dragonfly, Damselfly , Mayfly. (Exopterygotes)
    • The immature forms are called naiads and they differ in form, habitat and habit from the adults. The naiads are aquatic, breathing through tracheal gills and have external wing pads.
    • Adult stages are aerial.
2. Complete metamorphism. Eg: Butterflies, Moths
    • It is a complex metamorphosis and it is also called Holometabola.
    • Immature stages are called as larvae and it differ fully from the adult in form, mouthparts,habitat and habits. They also undergo an inactive stage called pupa (pl:pupae), from which  the adult emerges. The wing buds develop internally (Endopterygotes).
 Hypermetamorphosis. Eg: Blister beetles, stylopids and parasitic hymenopterans
          These insects undergo complete metamorphosis, but the larval instars differ in form, feeding habit and habitat.. The first instar larva is called triangulin and this type of development is called hypermetamorphosis.

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