18 HETEROPTERA OF EASTERN NORTH AMERICA. 



ments are called respectively the mesosternum and metasternum, 

 and their side pieces the meso- and metapleura. 



In most of the plant-feeding Heteroptera there is present 

 each side on the inner end of the metapleuron and near the 

 hind coxa a small opening known as the osteole (or ostiole). It is 

 usually borne upon a somewhat elevated and delimited area 

 of the metapleuron known as the osteolar peritreme. This osteole 

 is the external orifice of the stink gland, and through it is 

 emitted at the will of the bug a liquid or vapor which gives 

 off the characteristic odor of the insect. The visible portion 

 of the osteole varies greatly in form. Sometimes the rim of 

 the opening is expanded to form an auricle or is prolonged out- 

 wardly as an open canal-like duct. Again, the opening may be 

 at the end of a closed tube which extends outwardly on the 

 peritreme for some distance from the coxa. These variations 

 are used extensively in the classification of the Scutelleridae, 

 Anthocoridae and other families. 



Behind the pronotum and lying above the meso- and meta- 

 thorax and between the bases of the outer wings is the scutellum 

 or shield. This, in the Heteroptera, is usually much larger and 

 better developed than in other insects, sometimes covering al- 

 most the entire abdomen and outer wings. It is usually more 

 or less triangular in shape and, in certain families, its side 

 margins are furnished with a ridge or fold known as the fre- 

 iiiaii on which in repose the inner edge of the clavus rests. The 

 shape, size and sculpture of the scutellum are much used in 

 classification. 



The outer or front wings of the Heteroptera are known as 

 hemelytra (or in this work as elytra). They differ greatly in 

 texture and form from the inner ones and this, taken in con- 

 nection with their peculiar structure, gives name to the order, 

 the word Heteroptera meaning "diverse-winged." They close 

 above and in great part or wholly cover the abdomen, the basal 

 portion being more or less horny in texture, the apical one 

 usually membranous and overlapping. The thicker basal por- 

 tion of the elytron is divided into two parts, the corium or larger 

 outer portion and the clavus or narrow part lying next to the 

 scutellum and separated from the corium by the claval suture. 

 In the Miridae and allied families (fig. 1) the outer or costal 

 part of the corium is usually sharply delimited by a suture and 

 is called the embolium, while the apical triangular portion of 

 the corium is separated by the fracture and is known as the 



