44 PROC. ENT. SOC. WASH., VOL. 20, NO. 3, MAR. 1918 



segments composing the typical segment; and suggested that at 

 some time there might be found four sterna for these hypotheti- 

 cal sub-segments, proposing for them the designations praester- 

 num, sternum, sternellum, and poststernum (not " poststernel- 

 lum," which is Comstock's term), although he was unable to 

 detect them himself in any insect, and was therefore unable to 

 either figure or define them, merely supposing that they should 

 occur in some hitherto unstudied insect, on the erroneous suppo- 

 sition that each segment is composed of four subsegments. The 

 subsequent search for the sterna of these nonexistent subsegments, 

 has led to a chaotic confusion in the application of McLeay's 

 undefined terms, since any four consecutive sternal subdivisions 

 of the six shown in figure 14, is, ps, bs, fs, pfs, or ss could be desig- 

 nated by these terms; and if one is to use them at all, it will be 

 necessary to state in each case, that his application of the term 

 used is not that of this or that entomologist, for practically all 

 possible applications of these terms have been made, as will be 

 seen from the following discussion. 



Meinert, 1867, was among the first entomologists to apply 

 McLeay's terms to actual sternal subdivisions in insects. Meinert 

 employs the terms presternum, "sternum" and poststernum, to 

 designate three sternal subdivisions in Japyx, but, while the 

 plate which he calls the presternum, is the presternum, ps, of 

 figure 14, unfortunately, the plate which he terms the "post- 

 sternum," is homologous with the anteriormost sternite is of 

 figure 14, so that this usage of the term poststernum is hardly 

 admissible. Amans, 1885, on the other hand, applies the term 

 poststernum to any part of the sternum between and behind 

 the coxal cavities, while Petri, 1899, designates the region homol- 

 ogous with the meral region of the coxa as the "poststernum," 

 in the Diptera. 



Comstock and Kochi, 1902, erroneously conclude that the typi- 

 cal segment is composed of two subsegments, and propose that 

 the terms "sternum" and sternellum be applied to the ventral 

 rplates of these imaginary subsegments. In the only two instances 

 in which they apply the term sternellum to sclerites other than 

 rthe neck plates namely in their figures 12 and 13 of the meta- 

 sternum of Pteronarcys and Stenopelmatus the plate designated 

 as the metathoracic "sternellum" is the sternum of the first 

 abdominal segment in both cases. In the only other instances in 

 which they employ the term sternellum, the plates so designated 

 are in the neck region, and are the anteriormost sternites of the 

 prothorax. Thus, in their figure 5, of the head of Corydalis, 

 the "sternellum" is plate is of figure 4 (of the present paper), 

 while in their figure 22 of the head of Stenopelmatus, the "sternel- 

 lum" is plate ps of figure 14 (of the present paper) , the "sternellum " 



