Hexapoda 3 (insects)

Flight and wings - Flight data - antennae - legs - mouthparts - breathing - Insect records - Insects as Vectors of diseases in humans - 4 main functions of a sense of smell in insects - behaviour patterns - identification - insect FAQ

How insects breathe

Unlike our blood insect blood rarely has any special substances, such as haemoglobin, for absorbing oxygen, and the blood plays only a minor part in the breathing process. Oxygen in carried directly to the tissues through branching tubes called trachea, which are found in all but the most primitive of insects, and some very specialised internal parasites. A trachea is a flexible tube which branches into smaller tubes called tracheoles (see the drawing of a flea showing the trachea and spiracles below). The tracheal opening to the exterior is called a spiracle. These usually run down the sides of the insect body, and are most easily seen in a large caterpillar.In small insects diffusion through the tracheoles is sufficient to supply their needs. In larger insects abdominal pumping is necessary. This can be seen by watching a stationary insect, especially a bumblebee, its abdomen will pulsate. The spiracles act as valves to the outside, and most can be partly or completely closed. This also helps to reduce water loss from the body. Carbon dioxide escapes through the exoskeleton. Some insect living in water have a siphon, or breathing tube, (Water stick insect, Water scorpion), others have gills, (damsel fly nymphs, may fly nymphs), and others hold a bubble of water, (water beetles).

Frequently asked questions about insects

Does every insect go through metamorphosis?

No. Some such as the Thysanura (bristletails and silverfish) look the same all theri life after harching from the egg. Others are termed hemimetabolous, this means they go through a partial metamorphosis, e.g. the Orthoptera (crickets, grasshoppers and locusts). The young do resemble the adults, but often the adults will have wings, and these wings will develop more at each moult, so the metamorphosis is gradual. Others go through a complete metamorphosis and are termed holmetabolous, e.g. Lepidoptera (butterflies and moths). These have a resting stage (chrysalis, pupa, etc.) where the body changes completely from the young larval form to the adult form

Does every bug have compound eyes?