662 Laura Florence 



The muscles controlling the movements of the head lie in the anterior 

 part of the thorax and have their origin in the metathoracic apodeme 

 and in the strongly chitinized tergite of the prothorax. The elevator 

 and retractor muscles are six in number and originate in the metathoracic 

 apodeme, three on either side of the median line; the two median muscles 

 are inserted in the distal ends of the occipital apodeme, and the two lateral 

 muscles on either side pass cephalad and are inserted in the neck. The 

 two depressor muscles are made up each of three strands, and originate 

 in the dorsal wall of the pn.ithorax on either side of the elevator muscles 

 on the transverse median line of the first pair of legs. They pass obliquely 

 ventrad and cephalad, and are inserted as two short, stout tendons in 

 the chitinous ring of the neck on either side of the ventral median line. 

 The lateral movements are controlled by muscles made up each of four 

 strands. They originate in the dorsal wall of the prothorax laterad of the 

 depressor muscles, and pass obliquely centrad, where they are inserted in 

 the lateral borders of the prongs of the occipital apodeme at its distal end. 



The muscles controlling the legs originate in the metathoracic apodeme, 

 and if the dorsal surface of the thorax be carefully removed or if horizontal 

 sections be made through this region, the muscles are seen to have a stellate 

 arrangement with the apodeme as the center point of the star. A similar 

 condition exists in the pediculi infesting man, and has been figured by 

 Miiller (1915). There are in, all eighteen groups of muscle strands 

 originating in the apodeme, and th'-ee of these groups are inserted as stout 

 tendons — two in the dorsal articulation of the coxa with the thorax, 

 and one a short distance within the ventral wall of the coxa, in each leg. 

 Each group is composed of some five to seven strands, which vary in 

 length according to their point of origin in the apodeme. The muscles 

 passing to the first pair of legs are also sujiportcd hy the apodeme,- which 

 pass(>s from the prothorax to the prosternum, and if this be dissected out 

 it is seen to pass through some of the individual strands of the bundles. 



On the ventral surface of the thorax there is no muscle plate resembling 

 that of the pediculi infesting man, but two transverse muscle bundles, 

 passing, respcH-tively, between the ventral borders of the coxae of the 

 second and thii'd pairs of legs, are present and correspond to the intercoxal 

 muscles described by Miiller. 1'he anterior band consists of four strands 

 and in those are inserted the posterior arms of the apodeme of the prothorax 



