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General
There is not much difference between the respiratory and circulatory of caterpillar, pupa or lepidopteran and because most of this can be applied to nearly all insects, I prefer to use insect instead of caterpillar, pupa, moth of butterfly.
Respiratory
Mammals and birds have a substance in the blood called haemoglobin, which gives blood its red colour and allows transport of oxygen and carbon dioxide between the lungs and every cell in the body. Insects don’t usually have haemoglobin in their blood and certainly no lungs, they have a different way of breathing. On the sides of one or more segments there are openings that can be opened and closed, these openings are called spiracles or stigmata. By opening or closing the spiracles, the exchange of oxygen and carbon dioxide is regulated. Behind the spiracles is a very fine amazed system of tubes and trunks, these are called trachea. The walls of the trachea have spiral thickenings of chitin, this prevents the trachea from collapsing and folding. The system is so fine mazed that most cells can be provided of oxygen and carbon dioxide is led out, the remaining cells receive oxygen from hemocyanin that provides the transport of oxygen over short distance. Apart from the tubes of the tracheal system, there are trunks, which can be filled and emptied with muscle contractions and are used for temporary storage of oxygen and carbon dioxide, these also have an important function during the moulting of a caterpillar.
Circulatory
Blood circulation is also something that can’t be compared with the closed circulation we have. The veins and arteries that we have are not present and the insect blood (hemolymph) flows freely through the body of the insect. This is called an open circulatory system and provides the distribution of nutrients throughout the body. To get the hemolymph circulating, an insect has a tubular heart at the backside that runs over the entire length of the thorax and abdomen. Each segment has a heart chamber which is separated by valves which ensure that blood can flow in only one direction. The blood is pumped from the rear body with a peristaltic movement to the thorax, there it ends in an artery and travels a little further to the head where the artery ends. The hemolymph now moves freely through head, thorax and abdomen back towards the end where the cycle begins again.