metamorphosis metamorphosis

growth and development of an insect undergoes during its METAMORPHOSIS It is the change in growth and development of an insect undergoes during its life cycle from birth to maturity

types of metamorphosis There are four basic types of metamorphosis in insects. No metamorphosis Gradual metamorphosis (Paurometabola) Incomplete metamorphosis ( hemimetaboa) Complete metamorphosis

Ametabola (No metamorphosis) e.g. Silver fish

Life stages young one adult Egg

It is most primitive type of metamorphosis. The hatching insect resembles the adult in all respects except for the size.

(Incomplete metamorphosis) Hemimetabola (Incomplete metamorphosis) e.g. Dragonfly, damselfly and mayfly

Life stages naiad adult Egg

The young ones are aquatic and are called naiads They are different from adults They breath by means of tracheal gills The lower lip is called mask, which is hinged and provided with hooks for capturing prey Their habit and habitat vary. After final moult, the insects have fully developed wings suited for aerial life

(Gradual metamorphosis) Paurometabola (Gradual metamorphosis) e.g. Cockroach

Life stages Egg nymph adult

The young ones are called nymphs They are terrestrial They resemble the adults in general body form Their compound eyes and mouth parts are similar to that of adults

Both nymphs and adults share the same habitat They lack wings and external genitalia Wing buds externally appear in later instars The genitalia development is gradual Later instar nymphs closely resemble the adult with successive moults

Fig. 20.27

(Complete metamorphosis) Holometabola (Complete metamorphosis) e.g. Butterfly and moth

larva pupa Egg adult

Majority of insects undergo complete metamorphosis Larva of butterfly is called caterpillar Larva differs greatly in form from adult. Compound eyes are absent in larva Lateral ocelli or stemmata are the visual organs.

Their mouth parts and food habit differ from adults Wing bud development is internal When the larval growth is completed, it is followed by a period of in activity (prepupa) and transforms into pupa In the pupal stage, the larval tissues disintegrate and adult organs are built up

Hypermetamorphosis Blister beetle

Triangulin Pupa Grub Life stages adult Egg

Common in hemi and holometabolous insects More than one larval stage is common