STRUCTURES USED IN CLASSIFICATION. 



19 



cuneus. Where the two clavi (plural of clavus) meet behind the 

 apex of scutellum their suture or line of union is known as the 

 commissure. The membrane, or apical membranous portion of 

 the elytron, is usually veined, and in certain families, as the 

 Miridae, the veins unite to form one or more closed cells or 

 areoles. The elytra in some of the individuals of many species 

 of Heteroptera are often abbreviated. These are termed 

 brachypterous forms and in them the membrane, and sometimes 

 the clavus, is often absent or much shortened. 



The inner or hind wings of a bug are almost wholly mem- 

 branous and are little used in classification. When at rest they 

 are folded across the apical portion and concealed beneath the 

 elytra. 



The legs of a bug are six in number, arranged in pairs, one 

 pair being joined to each of the divisions of the thorax. They 

 are composed of five parts, viz. : the coxa or basal segment 

 which in the terrestrial families is united by a ball and socket 

 joint to the thorax; the trochanter, a small triangular segment 

 united to the base of femur and apical part of coxa ; the femur, 

 a long and usually stout segment which is often more or less 

 clavate and toothed or spined beneath ; the tibia, also long but 

 more slender, and usually with two or more rows of slender 

 spines or setae, and the tarsus or foot, which is composed of 

 one to three movable joints, the terminal one usually end- 

 ing in a pair of claws. In 

 many species the claws 

 have attached to their 

 bases a pair of slender 

 appendages known as 

 aro/ia, and sometimes an 

 accessory pair of pseuda- 

 rolia. In many species 

 of predaceous bugs the 

 front tarsi and femora 

 are raptorial or armed 

 beneath and otherwise 

 modified to form (fig. 3) 

 grasping or prehensile 

 organs, which are used to 

 catch and hold their prey. In the aquatic bugs part or all of 

 the tibise are often more or less flattened and beset with nu- 

 merous ciliae for aid in swimming. 



Fig. 3. Prehensile fore legs of bugs, a, of a 

 hog-louse : b, of a soldier bug, Podisus ; c, of an 

 ambush bug, Phymata. (After Lugger). 



