66 Annals Entomological Society of America [Vol. IX, 



conditions of the trochantin are illustrated in such insects as 

 Corydalis, Capnia, some Orthoptera, Trichoptera, Diptera, 

 'Coleoptera, etc. When the trochantin is present and not 

 ■completely fused with other sclerites, it always articulates 

 with the coxa. 



In the prothorax of Periplaneta the trochantin has become 

 transversely split into two sclerites, the upper and larger of 

 which has been termed trochantinus major (Crampton, '09) 

 (Fig. 3, tnm), and the lower and smaller the trochantinelle 

 (Crampton, '14) (Fig. 3, tnl). Other writers consider the 

 trochantinelle as the entire trochantin, but this is a mistake 

 as one can readily see by comparing the trochantin of the 

 prothorax with that of the meso- and metathorax, in which 

 it is not divided transversely into two sclerites. The end of 

 the trochantin which articulates with the coxa is constant in 

 position in all three thoracic segments and bears at its extremity 

 a small inward projecting process (Fig. 3, atn). In the pro- 

 thoracic segment the trochantin is fused with the episternum 

 for a short distance and is separated from the rest of the epi- 

 sternum and antecoxale, partly by suture and partly by mem- 

 brane (Fig. 3, tni). In the meso- and metathorax, the trochantin 

 is entirely marked off from the episternum and antecoxale by 

 membrane (Fig. 3, tno). 



In Periplaneta, the trochantin also has a distinct, heavy, 

 longitudinal suture, dividing it into an anterior and posterior 

 region, termed ante-trochantin and post-trochantin (Crampton, 

 '14) respectively (Fig. 3, atn, ptn). This suture occurs in the 

 trochantin of the pro-, meso-, and metathorax of the roach and 

 can be plainly seen. In the prothorax (Fig. 3, tni) where the 

 trochantin is divided into tw^o sclerites, this longitudinal 

 suture extends through both, thus showing that these two 

 sclerites are equivalent to the sclerites in the meso- and meta- 

 thorax which everyone admits is the entire trochantin. 



In the mesothorax of Corydalis the trochantin is partly 

 fused with the episternum and antecoxale. A part of it which 

 corresponds to at least a portion of the trochantinelle, projects 

 free and is partly constricted off from the rest of the trochantin 

 (Fig. 10, tnl). This would indicate that the trochantinelle 

 in the prothorax of Periplaneta is a detached portion of the 

 trochantin. In Corydalis the portion of the trochantin which 



