The Hog Louse 665 



there is a moderately stout band of muscle which is attached to the dorsal 

 and ventral cuticula between and in line with the bases of the pillars. 

 Within the lateral chamber of each of segments 3 to 8 there is a group of 

 five slender muscle strands, and in segment 9 there are six larger strands. 

 On the ventral surface these delicate strands are attached to the body 

 wall just below the strongly chitinized pleurite, and from there they pass 

 somewhat obliquely centrad and dorsad to the cuticula just within the 

 central border of the chamber. 



The leg muscles are similar in both sexes and show no unusual modifi- 

 cations except in those controlling the claw. Landois (1855 a: 33 and 

 1865 b:495) studied in part the leg muscles of the man-infesting pediculi, 

 and Miiller (1915 : 14) has figured the muscles of the leg of a female clothes 

 louse. As already said, Osborn (1904) described the musculature con- 

 trolling the tarsus and claw of the hog louse. There are four muscles in 

 each coxa, which originate in its articulation with the thorax and are 

 inserted in its articulation with the trochanter. Within the latter are 

 the flexor and extensor muscles of the femur, with their origin and insertion 

 in its proximal and its distal articulation, respectively. The flexor muscle 

 of the tibia is made up of a number of fibers which originate at intervals 

 along the dorsal wall of the femur and come together in one tendon for 

 their insertion in the ventral line of the articulation of the femur with the 

 tibia. The extensor muscle i-s made up of two bundles of fibers originating 

 in the articulation of the trochanter with the femur and in the proximal 

 dorsal wall of the femur; it ends in two tendons which are inserted in 

 the articulation of the femur with the tibia on the dorsal side of the leg. 

 In the tibia there is one large muscle, made up of a number of closely set 

 fibers which originate in the proximal posterior and ventral walls of the 

 tibia. The muscle passes along the whole length of the segment, midway 

 giving off a branch which is inserted in the base of the protractile disk. 

 On entering the tarsus the muscle becomes a tendon which ends in a 

 strongly chitinized process of a diameter somewhat greater than that of 

 the tendon itself. It is inserted in the ventral wall of the tarsus under 

 the base of the blunt process situated there, so that its anterior end lies 

 just within the border of the claw and is attached to its ventral curve. 

 The position and attachment of this muscle has been determined from 

 the study of mounts of gross specimens and from numerous dissections 

 of legs. It must be regarded as the extensor muscle of the claw, and the 



