The feelers are very small and are often hidden in cavities beneath the head.
It is therefore a haemocoel, the coelom of the developed insect being represented only by the cavities of the genital glands and their ducts.
These cavities communicate with the exterior through the gonad ducts, which have nothing to do with them, but whose coelomic funnels are taken up by them in the course of their growth.
The cells which line them and also the cavities of the tubes contain urates, which are excreted from the blood in the surrounding bodycavity.
Crystals are found as a rarity in the amygdaloidal cavities of igneous rocks.