ry 
646 LAURA FLORENCE 
hollow aculeus or sucker, with which it pierces the skin, and sucks the 
human blood.” He also described the pumplike structure in the head, 
the peristalsis of the alimentary tract, and the ejection of feces during 
feeding. Leeuwenhoek (1695) described the hook-bearing part of the pro- 
boscis and its eversion during feeding, in addition to other characteristic | 
actions associated with the process. | 
When fed in captivity, the louse moves its head back and forth close | 
to the surface of the arm and rapidly jerks the antennae up and down. 
Then, with the head held at right angles to the body, it seems to anchor 
itself to the skin, probably by the everted teeth of the haustellum. While 
the stylets are being inserted, the thorax and the abdomen are raised and 
gently rocked from side to side, and the claws make irregular scratching 
motions. After the insertion the insect is holding itself in a more or less 
straight line and at an angle of from 40° to 45° with the arm. As the 
feeding progresses the body is gradually lowered, until it rests on the arm 
and with its head forms an oblique angle The act of sucking blood 
can best be watched in freshly molted specimens. The blood is first seen 
anterior to the eyes in the pumping pharynx, which dilates and contracts | 
with great rapidity, driving its contents into the true pharynx (larynx of 
Enderlein), whence they disappear under the brain to reappear as a thin 
red line in the slender esophagus before this passes under the fat cells and 
muscle of the thorax. Throughout the process a continuous peristalsis 
passes along the whole alimentary tract, but this has manifestly no con- |i 
nection with the drawing of the blood, as suggested by Widmann (1915 a: 
290). It seems rather to be a means of removing from the posterior |! 
region of the stomach and from the intestine the débris of the preceding |} 
meal, since it is the habit of the hog louse — at any rate when kept and} 
reared in captivity —to continue feeding until not only all the feces, 
but also a drop of blood, have been ejected. The latter may be pushed? 
out by the interlocking of the six longitudinal folds of the epithelial lining 
of the intestine immediately behind the stomach, in order to prevent the}! 
escape of the blood from the mesenteron during digestion. At the first 
feeding after hatching, no blood has been seen to be ejected, and in someft 
cases after the second feeding feces but no blood have been ejected. Theft 
average length of a meal is from eight to twelve minutes, but sometimes 
it lasts from twenty to thirty minutes, and at the close the mouth parts 
are apparently withdrawn by a short jerk of the head. Occasionally lie 
Ly 
