70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



the coxal muscles "extensors" and "flexors," the "extensors" being 

 the lateral muscles, the "flexors" the mesal muscles, but this nomen- 

 clature ignores the relation of the muscles to the natural movements 

 of the coxae. Morison adds, however, that a further study "would 

 doubtlessly result in a better nomenclature" for the muscles and a 

 "more accurate statement of their functions." 



The fore coxae are attached by articular membranes to the pleuro- 

 sternal suspensorium of the prothorax with somewhat obliquely trans- 

 verse axes between weak pleural articulations and the furcasternum 

 (fig. II G) ; sternal articulations are absent, but the mesal angles of 

 the coxae overlap the furcasternal margins. Though the fore coxae 

 are thus freely suspended, their principal movements are forward and 

 backward. 



Each fore coxa has six muscles (fig. 13 C, D), two of which are 

 promotors, three remotors, and one an intersegmental retractor of 

 the propectus. Of the promotors, one (55) arises on the episternum 

 and is inserted laterally on the anterior margin of the coxa, the other 

 (34) takes its origin on the side of the prothoracic endosternum and 

 is inserted mesally on the anterior coxal margin. The remotors in- 

 clude two lateral muscles and one mesal muscle. The first lateral re- 

 motor is a long muscle (C, D, G, ^§) arising on the side of the pro- 

 notum at the base of the spiracular lobe (fig. 17 C), the second (jd) 

 a broad, fan-shaped muscle taking its origin on the ventral surface 

 of the supraneural bridge of the endosternum (figs. iiC, 12 C) ; 

 both muscles are inserted close together on the coxal rim shortly be- 

 hind the pleural articulation (fig. 13 D, §j, 56). The mesal remotor 

 {^y) is a slender muscle with its origin on the pleural apophysis 

 (fig. II C) and its insertion on the posterior mesal angle of the coxal 

 base (fig. 13 C, D). 



The sixth muscle of the fore coxa (fig. 13 C, D, G, j8) comes from 

 the mesothorax, where it arises on the anterior part of the median 

 sternal ridge that supports the superstructure of the pterothoracic 

 endosternum (fig. 22 C) ; it extends horizontally forward and laterally 

 (fig. 12 C, ^8) to its insertion on a small point of the coxal base 

 mesad of the pleural articulation (fig. 13 D). The pull of this muscle 

 can have little specific motor action on the coxa, but the two muscles 

 diverging from the mesosternal ridge to the fore coxae are evidently 

 retractors not only of the coxae but of the entire propectus, being thus 

 adjuncts of the intersegmental ventral thoracic muscles (fig. 12 C, 5^). 

 The intersegmental coxal muscle is classed as an "extensor" of the 

 coxa by Morison (1927), but the corresponding muscle in Vespula 



