Ant colonies > Internal structure of ants > Respiratory system

Respiratory system

The Respiratory System

The tracheae of ants are not unlike those of many other insects, as shown by Janet's studies (1902) Of Myrmica and other genera. In all ant-larvae there are ten pairs of stigmata or tracheal orifices occurring on the meso- and metathoracic and first to eighth abdominal segments. These stigmata also persist in the adult ant as small, round openings. According to Janet the meta­thoracic pair is closed in the Myrmicinae (Myrmica), but remains open in the Camponotinae (Formica) and Dolichoderinae (Tapinoma). Each stigmatic orifice leads into a short stigmatic trunk which is furnished with a very interesting valve by means of which it can be closed (Fig. 25).

The stigmatic trunks of the thorax and gaster bifurcate in an anterior and posterior direction and the two branches fuse on each side of the body to form a continuous longitudinal trunk. This is very large in the gaster, but much more tenuous in the thorax, where a second pair of more dorsal longitudinal trunks is formed, which, in the queens and males, supplies the wing muscles with air. The gastric trunks dilate and contract with the so-called respiratory movements of the external skeleton and in this manner the air is pumped into and out of the finest ramifications of the tracheae.

The gastric trunks are united by ventral, transverse, anastomosing tracheae and also give off segmental dorsal branches which break up into finer and finer ramifi­cations to supply the various viscera.