58 Annals Entomological Society of America [Vol. IX, 



region by Knoch. Kirby termed the epimeron and episternum, 

 the parapleuron, an interpretation accepted by Smith, '06. 

 Burmeister and also Voss applied the term parapleuron to the 

 episternum. Kolbe used it for a sclerite occurring in beetles, 

 situated behind the wing and between the tergum and pleuron. 

 Ritter's parapleuron is equivalent to the anepisternum or 

 upper region of the episternum. Others have used the term 

 parapleuron to designate various sclerites of the thorax. At 

 present there is no uniformity of opinion concerning the applica- 

 tion of the term even among Coleopterologists, by whom it is 

 chiefly used. 



Episternum. The episternum is also subject to great 

 variation in insects. It may consist of a single sclerite as in 

 the earwig (Fig. 8, esi), or it may be subdivided into an upper 

 and lower region as in Mantispa, Chrysopa, Corydalis, Tipula, 

 etc. -(Fig. 2, es2). The suture which divides the episternum 

 into two regions may extend clear across, making a complete 

 division, as in the mesothorax of Tabanus (Fig. 11, g) or only 

 part way, as in the mesothorax of Tipula (Fig. 1, g). In 

 Chrysopa and Mantispa (Fig. 13), the division is represented 

 by a narrow strip of chitin of varying width, extending inward 

 midway between the two subdivisions. This strip is probably 

 a part of the episternum which has become fused with the 

 precoxal bridge (Crampton, '14). It may, however, belong 

 entirely to the precoxal bridge, a projection of which extends 

 between the two subregions, but this latter alternative is very 

 improbable. The formation of this region in other insects 

 seems to indicate that it is a part of the episternum. Crampton, 

 '09, applied the term "median region," to this narrow strip of 

 chitin. This seems to be the only term which has been applied 

 to it. It hardly seems necessary to give this region a name 

 and consequently none will be used in this paper. 



When the episternum is subdivided, a condition found in a 

 great many insects, the lower division may be fused with the 

 sternum (Figs. 1, 2 and 11, stp). The episternum is separated, 

 from the epimeron by the pleural suture. In all insects, both 

 the episternum and epimeron extend from the coxal process to 

 the pleural wing process. This condition can be plainly seen 

 in most insects, but in some such as Tabanus, etc. (Fig. 11, stp), 

 the lower portion of the episternum of the mesothorax has 



