THE CANADIAN ENTOMOLOGIST. 175 



other main branch at once gives off the anterior dorsal girdle, and soon 

 after divides into two about equal branches, one of which is the ventral 

 trunk, and the other proceeds directly towards the mouth. This cephalic 

 trachea divides into two main branches, the dorsal one of which subdivides 

 into about eight long convoluted tubes that supply the sides of the head, 

 the other proceeding almost to the mouth-opening, sweeps around in a 

 conspicuous curve of over 90°, and then, breaking up into about three 

 twigs, continues straight forward to the edge of the body. 



The trunks from the second pair of spiracles divide each into two 

 main branches, each of which gives off a small branch, the lower 

 anteriorly and the upper posteriorly ; these branches at once divide into 

 a small number of convoluted twigs serving the immediately adjacent 

 viscera. The ventral branch proceeds to the ventral trunk, and the 

 dorsal forms the dorsal girdle. The third spiracle opens into a trunk that 

 immediately divides into an external and an internal branch. The 

 external branch soon separates into an anterior and a posterior division, 

 each of which breaks up into about twelve long twigs, serving the edge of 

 the body along the posterior part of the thorax and anterior part of the 

 abdomen. The internal branch proceeds to the ventral trunk, but first 

 gives off a small branch, which serves the adjacent viscera with about five 

 convoluted twigs. The anal spiracles are nearly as large as the anterior 

 ones. From each arises a ventral and a dorsal trunk, and at the point 

 of separation a third main branch at the side. From this branch arise 

 successively a series of about twenty-five long twigs serving the sides of 

 the abdomen. Besides these tracheal there are a few convoluted visceral 

 branches given off from the trunks as follows : About eight on the 

 anterior dorsal girdle, the same number on the anterior section of the 

 ventral trunk, two on the middle division, and about eight in the posterior 

 section, and the dorsal trunk gives rise to about four in the abdomen. 

 These branches, counting those on the two sides of the body, amount 

 altogether to about 264 twigs. The finer trachese divide rarely, if at all, 

 and are quite constant in their numbers. 



Some of the most striking points in this tracheation are : The sharp 

 distinction both in structure and origin of the visceral and lateral twigs ; 

 the fact that the twigs from one spiracle rarely invade the territory 

 occupied by those of another ; and, most peculiar of all, that the twigs 



