326 ZOOLOGY 
long, and are closely applied to the outside of the alimentary 
canal (Fig. 187). Each of them consists of a free end, which is 
usually white, and of a brown portion which bears numerous 
small side diverticula, giving the tubule a feathered appear- 
ance; they open into the small intestine. The cells lining 
the tubule contain crystals of uric acid, which are excreted 
through the rectum. 
The tracheal system, which carries air to every part 
of the body, communicates with the exterior by eight pairs 
of stigmata. The first two of these are situated close behind 
the base of the first and second legs, between the pro- and 
meso-, and meso- and meta-thorax respectively. The remain- 
ing six are found on the soft integument which unites the 
terga and sterna of the seven anterior abdominal segments. 
Each stigma is surrounded by an oval ring of chitin, and the 
opening can be closed by the action of certain muscles. It 
leads into a large trachea, which in the first thoracic stigma 
swells into a considerable vesicle ; from this two branches pass 
off and enter the head. The most dorsal of these unites with 
its fellow of the opposite side, and the single trunk gives 
branches both to the eyes and to the brain; the other branch 
also unites with its fellow, and supplies the antennae and 
mouth appendages. A third branch arises from the same 
enlargement and runs to the anterior pair of legs, and several 
smaller branches supply muscles. Besides these, a stout branch 
runs backward and opens into the main trachea of the second 
stigma; this bears in its course many oval tracheal vesicles 
(Fig. 187), and gives off branches to the elytra; two or three 
other branches with vesicles also pass backwards, and one of 
them supplies the second pair of legs. The main trachea from 
the second stigma gives branches to the membranous wings, 
the third pair of legs, and longitudinal branches which open 
into those of the adjacent stigmata. 
The abdominal tracheae are very regularly arranged; the 
six stigmata on each side open into a trachea, which immedi- 
ately divides into a dorsal and a ventral branch; these arch 
round, pass backward, and meet together again in the main 
trachea of the next segment. The dorsal and ventral arches 
of the last stigma unite to form a ring, and at the point of 
