20 HETEROPTERA OF EASTERN NORTH AMERICA. 



The Abdomen. — The abdomen or hind portion of the body of 

 a bug is composed of nine or ten more or less complete seg- 

 ments, so united as to be movable in a small degree. Each 

 segment is composed of two parts, a tergum or upper portion, 

 and a ventral or under piece. The ventral of the first or basal 

 abdominal segment is united firmly to that of the metathorax. 

 Seven or eight of the ventral segments of the bug have a small 

 opening near the ends or lateral margins. These are spiracles 

 or external openings of tubes which serve as air passages. The 

 side margins of the abdomen in the Heteroptera are usually 

 more or less flattened and expanded to form the connexivum (see 

 fig. 17), the upper and lower surfaces of the abdomen proper 

 meeting along its inner edge. 



The eighth and ninth ventrals of the bug are more or less 

 modified in both sexes. In the female they are known as genital 

 segments and in many species each bears a pair of processes so 

 modified as to form an ovipositor. This serves both as a cut- 

 ting instrument to make slits in the epidermis of plants and 

 also as a tube-like organ to place the eggs therein. In repose 

 the ovipositor is in great part concealed. In the male the last 

 ventral is modified to form a secondary sexual organ, also 

 known as the genital segment. It bears a pair of clasping 

 organs, the variations of which are, by some authors, much 

 used in classification. 



The above constitute the more important external parts of 

 a true bug, the characters of which are used in determining 

 the name and position of any member of the order Heterop- 

 tera. As will be seen in the pages which follow, these different 

 parts vary much in size and in form, but the names given to 

 them apply as well to the members of one family as to an- 

 other. By referring to the accompanying figures, and by ob- 

 serving carefully the parts of the specimen in hand, the be- 

 ginner need have little hesitation in deciding as to whether the 

 description agrees with that specimen. 



In order to simplify and shorten the keys and descriptions in 

 the main body of this work I have used in a modified form 

 many of the terms above mentioned. I thus use beak for ros- 

 trum, cheeks for jugae, elytra for hemelytra, joint for segment, 

 and antennal, dorsal, ventral, connexival, tarsal, etc., for the 

 different segments or divisions of the parts to which they per- 

 tain. 



