88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



The remoter (/) may comprise several tergal muscles inserted on 

 the meron region of the coxa. Besides the principal abductor (M), 

 there are usually several smaller muscles from the episternum to the 

 anterior lateral part of the coxal rim, some of which are probably 

 accessory promoters. The adductor (A^) and the rotators (K, L) 

 arise upon the sternum or upon the sternal apophysis. The posterior 

 rotator may be broken up into a group of muscles. In addition to 

 the muscles just described the coxal musculature of a wing-bearing 

 segment includes the epipleural muscles {E, F), already described 

 in connection with the wings. The first (£) may be regarded as 

 a part of the abductor system of the leg in its origin, but the second 

 {F), having no representative in the prothorax, would appear to be 

 a secondarily developed muscle. Both the epipleural muscles are 

 present in nymphal Orthoptera, where they apparently function as 

 leg muscles, since the basalar and subalar plates are here not separated 

 from the pleuron (fig, 26 B). 



The actual arrangement of the coxal muscles and their attachmer,\ts 

 to the base of the coxa are seldom so diagrammatically simple as 

 shown in figure 37 B. There are likely to be several muscles in each 

 set, and again it is not always possible to find a representative of 

 each group. The coxa itself is usually turned more or less at an 

 angle to the body, and its base is seldom a symmetrical plane at right 

 angles to its length. It is, therefore, often difficult to determine the 

 exact function of any particular muscle or set of muscles. Moreover, 

 it appears that the action of individual muscles may be changed in 

 consequence of modifications in the coxal articulations. When the 

 coxa, for example, is hinged to the sternum, and has its motions 

 limited to a forward and backward turning on a transverse or vertical 

 axis, its musculature is correspondingly reduced, and such muscles 

 as remain become either promoters or remotors. In the Dytiscidae 

 the hind coxae are immovable, constituting solid bases for the telo- 

 podites of the hind legs, which are the swimming organs. In Dytiscus, 

 according to Bauer (1910), each hind coxa retains, besides the sub- 

 alar wing muscles, only two of the normal coxal muscles, and these, 

 having their origin on the tergum, serve probably as accessory eleva- 

 tors of the wings. Since the data for a comparative myology of 

 insects are not yet at hand, no attempt can be made here to follow 

 the modifications of the coxal musculature in the various groups of 

 insects. 



In the telopodite, or that part of the leg beyond the coxa, the joints 

 bend either forward and backward, or up and down. The most 

 precise terms for the motions at the two types of joints are produc- 



