662 LAURA FLORENCE 
| 
The muscles controlling the movements of the head lie in the anteramt 
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 ae | 
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 griginate 
in the dorsal wall of the prothorax 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 areseen to have a stellate 
arrangement with the apodeme as the center point of the star. A sunilar 
condition exists in the pediculi infesting man, and has been figured by). 
Miller (1915). There are in all eighteen groups of muscle strands) 
originating in the apodeme, and three of these groups are inserted as stout 
tendons — two in the dorsal articulation of the coxa with the thorax, y 
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 supported by the apodeme, which}, 
passes 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, respectively, between the ventral borders of the coxae of the 
second and third pairs of legs, are present and correspond to the intercoxal 
muscles described by Miller. The anterior band consists of four strands, 
and in these are inserted the posterior arms of the apodeme of the prothorax}. 
