88 CLARENCE HAMILTON KENNEDY Vol. XXII, No. 3 



metathoracic spiracular trunks to the region of the gut just back 

 of the gizzard and two others that run from the spiracular 

 trunks in abdominal segment 8 to the region of the intestine 

 just back of the malpighian tubules. The tracheation of the 

 head is very definite but so far has not been homologized with 

 the parts of the system in the thorax and abdomen unless the 

 tracheas of the labium can be homologized with leg trachece. 



This study supports the theory that the wings are developed 

 from pleural folds as this feature can be positively homologized 

 from the larval pleural fold stage to the adult winged stage. 



The only other order the writer has examined is the Plecop- 

 tera. Here the tracheal system is greatly distorted by the 

 thoracic gills and the depressed body. A pair of neural trunks 

 are formed in the abdomen by the fusion of the sternal trachece. 

 A lateral abdominal trunk is well developed which is probably 

 homologous with the lateral trunk of the Zygoptera though 

 this may be found to be homologous with the dorsal trunk of 

 the Zygoptera. The thoracic trachea are less changed. 



The writer believes that this reference of the tracheal 

 branches back to those in a generalized abdominal segment 

 will give a solution to the homolgies of the tracheal systems in 

 the various orders of insects. He hopes soon to carry the 

 study farther. 



