Insect Metamorphosis (Theory)

Metamorphosis in Arthropods

Some insects, fishes, amphibians, molluscs, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a  change of nutrition source or behavior.

Metamorphosis is the common phenomenon occurs in arthropods. The arthropods passes between stages by moulting its exoskeleton. After moulting new exoskeleton get inflated and then hardens. By successive several moulting an insect reaches final adult stage.

“Metamorphosis is a biological process by which physical development of an animal is takes place  after birth or hatching”.

Or

Thus, Metamorphosis is the process in which transformation of an immature larva into a sexually mature reproducing adult of vary different forms, structure, and habits.

Insect Metamorphosis (development).

The young creature of insect just hatching from an egg  is called either a larva, nymph, or naiad. After emergence from egg larva feed and grows faster. When these larvae or insects grows is size their skin shed off at regular interval called as instars and finally develops into an adult. The instar is differing from insect to insect. The instar also affected by environmental factors such as temperature, humidity and supply of food.

Thus  during development insects go through a series of changes as they develop from the egg to adulthood. This process of growth is called metamorphosis.

Types of metamorphosis in insects:

1.     No-metamorphosis

2.     Incomplete metamorphosis

3.     Gradual metamorphosis

4.     Complete metamorphosis

1.     No-metamorphosis : it is also called as ametabolous development. After hatching young creature of nymphs are resembles with adult in food and habitats except size. The adults and nymphs are wingless. The nymphs grows in size with each instar until reaches maturity.

         Eg. Silver fish.  (Lepisma ), Spring tail.

2.     Incomplete metamorphosis : it is also known as hemimetabolus development.  

In this type of metamorphosis  young creature pass through three stages of development viz.

1.    Egg,

2.    Naiad

3.    Adult

Young creature hatches from egg and then through several stage of development are nymph or naiads. Nymph look like adult except size and absence of wing nymph. Nymphs or naiad are aquatic and respire through gills.  The adult have wings and leads terrestrial or aerial mode of life near water  and respire with trachea. The nymph under goes moulting and at the final nymphal stage then moults into the adult.

Eg. Dragonflies, Mayflies, Stoneflies etc.

4.     Simple or Gradul metamorphosis : such type of metamorphosis is also known as pauro-metamorphosis. In this type of metamorphosis newly hatched creatures resembles with an adult in general body form, but they lack wings and external genital appendages. The youngs or nymphs undergoes several nymphal stages through successive moulting to become an adult.

Eg. Grasshopper, Aphids, Sting bug etc.

Gradual metamorphosis in bug

5.    Complete metamorphosis : it is also known as Holometabalous development.

In this type of metamorphosis the creature has to pass four developmental stages to become adult includes,

1.     Egg      

2.     Larva    

3.     Pupa         

4.     Adult. 

Complete or Holometabolous metamorphosis in butterfly

 The young is called larva which are familiar as caterpillar, magots or grubs which are completely different from adults. After hatching from eggs larva get moults several time to become full grown before pupating within a secreted case around body called the puparium. In this stage  larva get differentiate into adult within pupa having legs, wings antennae. The young breaks the puparium and adult insect emerges from the pupa having fully functional reproductive organs.  

Eg: Buterfly, Mosquito, Housefly etc.