504 



THE STUDY OF INSECTS. 



tions by a suture which extends transversely a short distance in front 

 of the caudal margin ; the smaller sclerite which borders the posterior 

 coxae in front and often passes between them is called the ante-coxal 

 piece of the metasterum (Fig. 611, 16 z 1 ). 



The openings in the thoracic segments in which the legs are in- 

 serted are termed the coxal cavities. Much use is made in the classi- 

 fication of beetles of the form of the coxal cavities of the prothorax. 

 When the epimera of the prothorax extend behind the coxae and 

 reach the prosternum, the coxal cavities are said to be closed (Fig. 612) ; 



FIG. 612. Prothorax of 

 Harfalus; c, coxa ; em, 

 epimeron ; es, epister- 

 num; /, femur ; , pro- 

 notum ; s, s, s, proster- 

 num. 



u 



FIG. 613. Prothorax of 

 Pent he ; c, coxa ; cc, 

 coxal cavity; _/", femur; 

 j, prosternum; t, tro- 

 chanter. 



FIG 614. 



when the epimera do not extend behind the coxae to the prosternum, 

 the coxal cavities are described as open (Fig. 613). 



The Legs. The parts of the leg are described on page 62. In ad- 

 dition to what is said there it should be noted that in beetles the 

 coxae of the hind legs are frequently broad plates which appear to 

 belong to the fixed parts of the thorax, differing greatly in form from 

 the fore and middle coxae (Fig. 611, i7 a ). 



In many beetles there is a small sclerite which is supposed to be an 

 appendage of the coxa ; this is the trochantin (tro-chan'tin) ; the tro- 

 chantins of the fore and hind coxae are represented in Fig. 6n,and 

 are lettered i7 al . 



The student should understand clearly the numbering of the seg- 

 ments of the tarsi. In counting these segments the claws borne by 

 the last segment are not included, but the segment that bears these 

 claws is counted. This fact should be carefully noted. We have 

 found that students are very apt to omit counting this segment, espe- 

 cially when it differs in form from the preceding segments. Two of 

 the more common types of the tarsi of beetles are represented in Fig. 

 614, with the segments numbered. 



Students wishing to carry their study of beetles beyond the scope of 

 this text-book should procure the" Classification of the Coleoptera of 



