56 Annals Entomological Society of America [Vol. IX, 



infra-epimeron. Crampton, '08, used the terms hyper- and 

 hypo-epimeron for these regions, but on account of the sim- 

 ilarity of the terms he later (Crampton, '09), discarded them, 

 substituting in their place anepimeron and katepimeron. 



Osten-Sacken's terminology has been widely used for the 

 Dipteron thorax and is very good. Crampton, '14, retains it in 

 a slightly modified form, viz. : changing the ending from pleura 

 to pleurite. Thus in the Diptera, Crampton, '14, terms the 

 upper region of the epimeron the pteropleurite (situated beneath 

 the wing base (Fig. 1, ptp) and the lower region meropleurite 

 (usually fused with the meron, especially in Diptera (Figs. 1 

 and 11, mp). These terms will be adopted in this paper. 



Some Diptera such as Tipiila, Chrysopa, etc., have the lower 

 portion of the epimeron separated from the meron by a suture. 

 In such cases the term katepimeron (Crampton, '09) will be 

 applied to the lower portion of the epimeron (Figs. 1, 2 and 13, 

 kem). The term meropleurite will be applied to the katepimeron 

 plus the meron whether these sclerites are completely fused into 

 one as in the mesothorax of Tabanus (Fig. 11, mp), or separated 

 by a suture as in Tipula and Chrysopa (Figs. 1 and 13, mp). In 

 either case the meropleurite represents identical regions (Figs. 

 11 and 13, mp). 



The subalar plate or its representative is always present 

 behind the pleural wing process (Figs. 1, 2 and 11, sa). It may 

 be partly fused with the epimeron or entirely separated from 

 it by membrane. Both of these conditions can be found in the 

 Diptera {Leptis, Tabanus, etc.. Figs. 1 and 2, sa). Sometimes 

 the subalar plate is divided into two sclerites as in some of the 

 Plecoptera, and in that case will be termed anterior and poster- 

 ior subalar sclerites (Crampton, '14). In some Leptidas and 

 Tabanidae, there is a cleft immediately below the subalar 

 plate (Figs. 2 and 11, sa), which is prolonged downward into 

 the epimeron (pteropleurite, ptp) for a short distance in the 

 form of a suture, but the internal ridge of this suture is not 

 continuous with the pleural suture. Snodgrass, '10, mistook 

 this suture for the pleural suture, which it closely resembles 

 when viewed externally. By carefully examining a specimen 

 which has been boiled in caustic potash, the mistake will be 

 readily discovered and the real pleural suture can be easily 

 traced by means of the apodeme, from the coxal process into 

 the pleural wing process (Figs. 2 and 11, plso). 



