Doering: Lepyronia quadrangularis. 551 



is irregular in shape, about as wide as long;, and approximately 

 equal to the lengtli of the sternum. It is separated from the sternum 

 by a distinct transverse suture. There is no precoxale bridge. 



The epimeron (pi. LVH, fig. 10) is an elongate selerite extending 

 the entire length of the mesothorax. It is widest just behind the 

 middle when \ie\ved ventrally, and bears the postalare bridge, 

 connecting it with the postscutellum just cephahid of its broadest 

 point. The epimeron is partly divided longitudinally by a suture 

 which runs parallel to the pleural suture, but which extends for only 

 lialf its length. Like the episternum, it is fused to the sternum, 

 being separated by the pleural suture. 



The sternum (pi. LVII, fig. 10) of the mesothorax is composed of 

 three sclerites — the presternum, the sternum proper, and the 

 sternellum. The anterior one is the presternuni (pi. LVII, fig. 10), 

 which is a narrow collarlike selerite, bounded laterad by the 

 episterna and caudad by the sternum itself. It is slightly less 

 chitinized than the sternum, especially towards its lateral margins. 

 Along its anteromedian margin is a broad indentation into which 

 the troughlike sternum of the prothorax is inserted. 



The sternum (pi. LVII, fig. 10) is the major selerite of the ventral 

 part of the mesothorax. It is a bilobed selerite, each lobe being 

 somewhat inflated. They are separated from each other by a heavy, 

 dark median line which resembles a suture. Just before this line 

 reaches the caudal margin of the sternum it extends laterad as a 

 short cleft which marks off a little flap on each lobe. The sternum 

 is heavily chitinized and very dark colored. It is closely associated 

 with the pleural sclerites, as was mentioned above, but is separated 

 from both by very distinct and heavy sutures. 



The sternellum (pi. LVII, fig. 10) is a partly membranous, partly 

 chitinous selerite, lying directly caudad of the sternum. It is a 

 rather ill-defined region, somewhat semicircular, with its caudal, 

 convex margin joined to the concave cephalic margin of the pre- 

 sternum of the metathorax. The chitin is deposited along the 

 middle line of this selerite as a broad, longitudinal band which sends 

 out two lateral arms at its cephalic end which are entirely hidden 

 by the overlapping sternum, and two lateral arms at its caudal 

 end. The part of the sternellum which is chitinized is not very 

 heavy, due to the fact that the large coxae entirely cover it. 



The trochantin (pi. LVII, fig. 10) is a very small but distinct 

 selerite, located between the laterocaudal angle of the sternum and 

 the laterocephalic angle of the coxa. 



