240 Annals Entomological Society of America [\o\. XI, 



(psl). In most families the scutellum (si) is very prominent, 

 and is always to be seen between the closed forewings, extending 

 backward over the succeeding segment and terminating usuallv 

 in a point. In some forms the scutellum (si) becomes unusually 

 extensive. In the Pentatomidae it reaches beyond the meta- 

 thorax and projects over the abdomen, in the Scutelleridae it 

 extends still farther, while in the Thyreocoridas (Figure 25) it 

 almost conceals the abdomen. The postscutellum (psl) is 

 always closely attached to the anterior part of the next segment 

 so that it is frequently difficult to ascertain its posterior limit. 

 A prealare (pra) is almost invariably found in the mesothorax 

 throughout the Heteroptera, and together with the antero- 

 lateral margin of the mesonotum and the upper anterior margin 

 of the mesopleuron, it forms the boundary of an irregular, often 

 more or less triangular, membranous region (i. e., the region 

 posterior to pra, ventral to psc and dorsal to aba and es). In 

 front of the prealare (pra) the spiracle, surrounded by its peri- 

 treme (pt), is usually to be seen. The postalare (poa) is usually 

 narrow and often almost indistinguishably fused with the 

 prescutum (psc) of the metathorax. 



Pleuron. The mesopleuron exhibits a considerable degree of 

 diversity in the suborder. Along the upper margin of the epi- 

 sternum (es) there is usually marked off a narrow plate (aba), 

 probably the anterior basalare, which has become fused to the 

 episternum. This fusion occurs in most Heteroptera. Often 

 the posterior basalare (pba) is also distinguishable, usually above 

 the anterior basalare; this, too, is often fused to the episternum. 

 This plate (pba) occurs in the Emesidae (Figure 14), Berytid^s 

 (Figure 22) and Coreidae (Figure 23). 



In nearly all the Heteropterous families studied (except in 

 the Notonectidae, Nabidae, Cimicidae and Capsidae) the pleural 

 plates extend down over the upper part of the coxa (ex). In 

 such cases the lower part of the pleuron is divided by a cleft (c) 

 extending lateral to the coxa and terminating in the coxal 

 articulation (x). From this coxal process, as the articulatory 

 projection of the pleuron is called, the pleural suture, when 

 present, extends dorsad. In the Heteroptera it is more often 

 absent, being entirely visible only in the Corixidae (Figure 19), 

 Notonectidae (Figures 15 and 16) and Belostomatidae (Figure 

 18). In the Nepidas (Figure 17), Capsidae, Reduviidae, and 

 Thyreocoridae (Figure 25) it is visible in part, extending dorsal- 



