Tur Hoc Louse 663 
od prosternum. It lies just anterior to the stomach, below the esophagus, 
nd is covered ventrally by the thoracic ganglia and many fat cells. The 
osterior band consists of two strands and passes across the ventral 
irface of the stomach. From each of the points of its insertion in the 
oxae of the third pair of legs, amuscle passes somewhat obliquely cephalad, 
nd these muscles are inserted in the posterior arms of the apodeme 
there they enter the anterior transverse muscle band. In sections made 
rough lice having the stomach filled with blood, the transverse muscle 
ands appear to be imbedded in the stomach, owing to its walls having 
ecome distended on either side of them. 
The work of Landois and of Miiller has made known the great difference 
. the longitudinal abdominal musculature of the two sexes of the man- 
vfesting louse, and Nuttall (1917 a:296) has summarized this difference 
3 follows: 
q 
| 
; 
Dorsal abdominal Ventral abdominal 
muscles are present muscles are present 
: under segments under segments 
Rule sina cpr is eres yc- asf clate aids atanehe aidis es Deol ONO EES 2+ 3, 4, 5,6 
. WG TEES s seocco god Dee AEA e ce ees GAAS Mo By 
1 the hog louse no such difference is found. In both sexes a dorsal 
uscle extending the whole length of the abdomen is present. It consists 
‘some eight muscle strands on either side of the median line. In segment 
these strands converge to the point of their attachment to the posterior 
uwiace of the metathoracic apodeme, and posteriorly, in segments 8 and 
the two halves of the plate diverge and the heart lies between them. 
he contraction of the muscle plate raises the posterior end of the abdomen. 
1 both sexes the ventral muscle plate (Plate LIX, 4) begins in the anterior 
prder of segment 2 and extends caudad to the posterior border of segment 
The number of strands in each segment is apparently not arbitrary, 
id the following have been found most frequently: 
Number of strands Number of strands 
in male in female 
Segment 2, 12 central and 4 lateral 10 central and 4 lateral 
Segment 3, 14 18 
Segment 4, 14 16 
Segment 5, 14 16 
Segment 6, 14 16 
