Insect Stages, Growth and Development

Reported by:Arenda, Clarise D.Valdecantos, Anjeline R.

DEFINITION OF TERMS:• Metamorphosis - the transformation of a larva, nymph,

or naiad into an adult insect.• Hemimetabolous Metamorphosis – incomplete

metamorphosis• Holometabolous Metamorposis - complete

metamorphosis• Ametabolous Metamorposis- no change in the body

form of insect.• Eclosion- is used to denote the process of hatching or

exciting from the egg.

• Instar - a developmental stage of arthropods, such as insects, between each molt (ecdysis), until sexual maturity is reached.

LIFE CYCLES

• The vast majority of insects lay eggs, and the development of the embryo progresses outside the mother’s body.

• Most species undergo metamorphosis. Nearly all insects display either hemimetabolous metamorposis or holometabolous metamorposis.

• Few change so little, except in size, that they said to have ametabolous metamorposis.

INCOMPLETE METAMORPHOSIS

HEMIMETABOLOUS insects are usually distinguished by immature stages, called nymph, that resemble adults, the main changes being an increase in size and the development of sexual organs and wings.

Examples: Dragonflies, damselflies, mayflies and stoneflies.

COMPLETE METAMORPHOSIS

HOLOMETABOLOUS insects consists of four distinct stages:1. From the egg hatches a larva.2. Larvae molt several times to accommodate growth. 3. At the end of the larval stage, a final molt may occur with the pupa emerging. • A great transformation is occurring. The developing wings

can often be seen, as can the compound eyes, antennae, mouthparts and legs.

4. At the eclosion, the adult emerges, within hours the wings unfurl, becoming stronger as the veins dry and stiffen, and the exoskeleton dries, hardens and gains pigments.

INSTAR• It denote the developmental stage of

the larval or nymphal forms of holometabolous (complete metamorphism) or hemimetabolous (incomplete metamorphism) insects, but the term can be used to describe any developmental stage including pupa or imago (the adult, which does not molt in insects).

AMETABOLOUS METAMORPHOSIS

AMETABOLOUS insects emerge from eggs into immatures of virtually the same shape as the adults. They're considered ametabolous because the insects simply get bigger and do not undergo any distinct rearrangements of body structures between the immature and adult stages.

EGG STAGE

• Eggs are laid on plants by the adult female butterfly. These plants will then become the food for the hatching caterpillars.

• Eggs can be laid from spring, summer or fall. This depends on the species of butterfly. Females lay a lot of eggs at once so that at least some of them survive.

• Butterfly eggs can be very small.

LARVAL STAGE OF INSECTS

• Primary functions are to eat and grow.• Wormlike in appearance • Posses a series of simple eyes, chewing-

sucking mouthparts, a pair of very short antennae, and sometimes three pairs of true legs.

• Developing wings are hidden in the cuticle.

PUPA STAGE• When the caterpillar is full grown and stops

eating, it becomes a pupa. The pupa of butterflies is also called a chrysalis.

• Depending on the species, the pupa may suspended under a branch, hidden in leaves or buried underground. The pupa of many moths is protected inside a cocoon of silk.

• This stage can last from a few weeks, a month or even longer. Some species have a pupal stage that lasts for two years.

• Special cells that were present in the larva are now growing rapidly. They will become the legs, wings, eyes and other parts of the adult butterfly. Many of the original larva cells will provide energy for these growing adult cells.

ADULT STAGE OF INSECTS

• The adult stage - also called the imago - is often capable of moving quite long distances in order to colonize new areas, and insects may perform special routines in order to find or attract a mate.

• After mating and (internal) fertilization, eggs are laid, usually near to a potential source of food.

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