1916] Thoracic and Cervical Sclerites of Insects 59 



become fused with the sternum. Many workers have con- 

 sidered this fusion product of sternum and lower portion of the 

 episternum as the entire sternum and accordingly termed it the 

 sternum. This misinterpretation has led to great confusion in 

 the terminology. In the mesothorax, Lowne termed this 

 composite region the "mesoplastron. " He also applied the 

 term, " metaplastron " to the meropleurite (lower portion 

 of epimeron fused with the meron) of the mesothorax (Fig. 

 11, mp). Chabrier had originally used the term "plastron" 

 to designate the pleuron of the prothorax, so that Lowne is 

 incorrect in stating that the " mesoplastron " is the "plastron" 

 of Chabrier. Packard, '80, used the terms sub- and infra- 

 episternum to designate the fusion product of the sternum and 

 lower region of the episternum. Snodgrass, '10, and several 

 other workers termed it the "sternum." Osten-Sacken, '89, 

 used the term " sternopleura. " Crampton, '09, designated it 

 by the component parts entering into its composition, but later 

 Crampton, '14, adopted Osten-Sacken's terminology, slightly 

 modified, calling it the sternopleurite. The latter term will 

 be used in this paper. 



The lower portion of the episternum in Chrysopa and like 

 insects has a new region marked off, which is composed of a 

 different combination of sclerites than the region representing 

 the sternopleurite in Tabanus, and hence has been termed 

 pleurotrochantin, (Crampton, '14) (Fig. 13, pltn). This term 

 will be retained in this paper. The pleurotrochantin is com- 

 posed of the lower part of the episternum, most of the trochantin 

 and the antecoxale. The term sternopleurite, however, will 

 still be applied in Chrysopa and like insects, to the pleuro- 

 trochantin plus the precoxale and sternum (Fig. 13, stp), since 

 this region would then be identical with the sternopleurite of 

 Diptera (Fig. 11, stp). In this way a uniformity of terminology 

 is retained. 



The upper region of the episternum is a more or less square 

 sclerite, which has become pushed forward in the mesothorax 

 of such insects as Tabanus (Fig. 11, esp), due to the shifting 

 forward of the parts as previously mentioned. The upper margin 

 of this sclerite and also the pteropleurite (upper portion of the 

 epimeron) often contain clefts of varying depth and width 

 (Figs. 2 and 11). The shifting forward of sclerites naturally 

 led to their misinterpretation by different workers and finally 



