Vol. XXV ] ENTOMOLOGICAL NEWS 21 



In front of the pleural plate, there occur, in some insects, a 

 small group of plates, the interpleurites, Ip (Figs. 2, 3 and 4) 

 which will be discussed with the remainder of the interseg- 

 mental plates under the heading intersegmentalia. In addi- 

 tion to these may be mentioned the peritreme, Pt (Figs, i, 2, 4, 

 5 and 6), which surrounds the spiracle or breathing pore. The 

 spiracle is regarded by many investigators as belonging to the 

 segment behind it. 



STERNITES In such primitive insects as the stoneflies 

 Ca\pnia and Leuctra, there are five distinct sclerites in the ster- 

 nal region, and traces of certain of these sternites are pre- 

 served in some insects, although the most of them disappear 

 in the higher forms, either through fusion with each other, or 

 through a fading out of the pigment and the softening of the 

 chitinous deposits which formed them. 



The sternite which is tentatively designated as the fore- 

 most of the principal sternal sclerites, is the prebasisternite. 

 Pbs (Figs. 2, 3 and 5), which is probably a derivative (or de- 

 tached portion) of the large sternite behind it, called the 

 basisternite, Bs (Figs, r, 2, 3, 4, 5 and 6). The basisternite, 

 as the name implies, forms the lower portion of the sternum 

 in many insects ; its lateral wings Lst, previously described, 

 forming the sternal portion of the flanks. These lateral ex- 

 tensions may become detached to form separate plates, the 

 latero sternites, Lst ( Fig. i ) as in the earwig, or they may re- 

 main connected with the sternum, and unite witjj the pleural 

 plate to form a pre-coxal bridge extending between the pleural 

 and sternal regions. The basisternite may be split up by 

 diagonal fissures, into four sclerites, as in the prothorax of the 

 roach Ectobia (Fig. 3, Bs). The basisternite is retained in 

 practically all insects, and forms the principal sclerite of the 

 sternal region. 



Behind the basisternite is the fur cast emit e, Fs (Figs, i, 2, 

 3, 4, 5 and 6). As the name implies, it bears the furca, or 

 fork-like apophyses (internal sternal processes). The 

 apophyses may be separated from each other, one on either 

 side of the median ventral line (i. e., diapophyses), or they may 

 approach each other in the median line, and their bases unite, 



