INTRUDUCTIUX. XXIU 



Legs. — Tlie first joint of tiie legs, or that by wliicli they are 

 attached to the body, is called the coxa, and is received in appro- 

 priate cavities ; the anterior coxal cavities are surrounded by the 

 .prosternum and adjoining- pieces, usually the epiuiera, the epi- 

 sterna never reaching the coxal cavity proper; the cavities are 

 frequently open behind, and rarely in such cases completed by 

 the close apposition of the niesosternum. On the outer side of 

 the ^interior and middle coxie, an additional piece is sometimes 

 observed, which is sometimes connate with the coxa>, and often 

 independently movable, this is called the trochantin, and to the 

 additional space formed for the reception of it, the episterua 

 often reach - 



The middle coxte are surrounded by the nieso- and metasternum ; 

 when the closure is not complete the coxal cavities are said to be 

 open externally, in which case a trochantin is often visible, and 

 the epimera reach the cavity; occasionally, as in CarabintB, the 

 epimera form part of the outer margin of the cavity without any 

 trace of trochantin. 



The hind coxte are placed between the metasternum and the 

 first segment of the abdomen ; the latter extends along the outer 

 edge anteriorly so as to reach the side pieces of the metathorax, 

 though frequently this junction can only be seen on raising the 

 elytra. 



The form of the coxae is of the greatest importance in distin- 

 guishing the families. 



On the under side of the prothorax a breathing ])ore, s/icpno. 

 or spiracle, is sometimes observed ; it is usually placed behind 

 the outer limit of the coxal cavity. 



At the extremity of the coxa, and between it and the femur is 

 situated a small piece called the trochanter ; it varies in form, 

 being usually situated in the axis of the thigh, and is more or less 

 obliquely cut off; in many families the trochanters of the hind 

 legs are quite prominent at the inner margin of the thighs, and 

 connected witli them only at the base; rarely the trochanters are 

 greatly prolonged, and in one species of Patrobus are even slightly 

 longer than the femur. 



The first long piece of the legs is called the thigh ov femur ; 

 following it is the ti.lna. The form of the legs varies greatly in 

 d liferent families; being either fitted for walking, ambulatoiial ; 

 digging, /ossor/'a/,- or i^\s\\\n\Vm^, natatorial : in the latter form, 



