The outside skeleton of an insect gives it no room for expansion. One would expect the inside of the insect to grow faster than the outside since the skeleton of most insects is made of keratin and that forms slowly. So growing insects must periodically moult. Moulting is a form of 'undressing'. The horny casing splits and the insect creeps out in such a soft skin that for a brief period it looks naked, or boneless if we have to say. To ensure the new skeleton forms in a suitably bigger size, the insect swallows air or water, gulping and swelling until it attains a size bigger than its normal size. Then the insect waits while its roomier skeleton hardens around it. It may take several hours, like the shell of a bird that is laid soft and hardens on contact with outside air.
The insect’s blood is not confined by any system of veins like ours is. From its single great artery, which runs from the heart through the chest, the blood surges and seeps through the whole body. The blood is forced to the far tips of the thread-fine extremities by little auxiliary hearts – call them 'pump stations' – with sets of powerful muscles, located along the pipeline wherever there is some difficulties and a little boosting is required. A cockroach, which most of us are familiar with, has a heart in its head, which pumps blood through its long feeler that grows from the side of its head just above the eyes. Without the heart, it would be difficult to keep the feelers alive with blood circulation since the feeler are in use all the time that the cockroach is moving about. Some water insects have hearts on their legs to booster perfect circulation of blood as the insects uses the legs to swim.
For an insect, drawing the breath of life involves another remarkable process because it has no lungs, nor does it breath with mouth or nostrils. Along its side are symmetrical rows of tiny perforations. Each of these perforations is an air duct. Inside the body, they link into two main trunk lines, which branch into hundreds of air lines running to every area of its body. Thus the whole insect is continuously ventilated by a flow of air which it controls by opening and closing of the air ducts, just like the musical organ player pulls stops and opens others to produce a sound he chooses.
When an insect is resting it needs relatively little oxygen. But in flight, it must breathe fast and prodigiously. It must be able suddenly to call upon as much as 50 times as much air as it would normally require. Its beating wings bring this about. As the wing muscles contract, they force out almost all the air in the system. As the wing muscles relax, fresh air from outside rushes in to occupy the vacuum. The oxygenation provided by the action of a flying insect is so complete that even in its wing muscles there occurs an almost complete change of air at every wing beat.
No aspect of the dynamics of an insect’s body presents more striking powers than its wings. A dragonfly, carrying its long body on a pair of wings thinner than a fine paper edge, can reach a speed of about 60 kilometres per hour. A mosquito, gorged on blood to the full, performs an extraordinary aerodynamic feat of flying off carrying a load twice its own weight. To do so, it has to beat its wings more than 300 times a second. Such a furiously rapid wing beat is by no means a unique performance. When we hear the high, thin whine of a midge, so small a fly that it is almost invisible as it moves around our eyes irritating us incessantly, the midges wings are beating at close to 1000 times per second.
Insects that do not fly, their blaze of energy is concentrated in special adaptations that result in equally impressive display of power. Look at the flea. Either jigger flea or dog flea can be able to power up its jumping feat and hop over an object 100 times its height. If that was a human, we are talking of a man able to jump over KICC building, or higher, in one leap. That is not all about insects. Take time to learn about an insect that you see regularly at home. It is an interesting affair.