Monday, April 23, 2007

Life of an Insect

Because insects have a tough, non-living outer covering or exoskeleton, they cannot grow steadily, but have to grow in stages by periodically shedding the exoskeleton. This process is called moulting or ecdysis. The stages between moults are called instars.

Although some insects give birth to active young (notably the summer generations of aphids), the vast majority of insects lay eggs. When the young insect is ready to leave the egg it either chews its way out or bursts the egg shell by muscular action, sometimes assisted by sharp spines on its body covering.

The apterygote (or wingless) insects, and some of the species which have lost their wings secondarily during the course of evolution, hatch in a form very like that of the adult except for the lack of reproductive organs. Apart from an increase in size there is little visible change in appearance as the insect grows (i.e., little or no metamorphosis).


Angela Ward said...

Do the new shells form underneath the old shell until it is complete, then the old shell is shed? Or, do the new shells form after the shedding of the old one?

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