s rather to be compared
to a delicate elastic probe, in the use of which the terminal lobes
probably serve as feelers. As soon as the capillary system is reached,
the blood will at once ascend into the narrow tube, after which the
current is continued with increasing rapidity by means of the pulsation
of the pumping ventricle and the powerful peristaltic movement of the
digestive tube."

[Illustration:[7]111. Mouth of the Louse.]

If we compare the form of the louse (Fig. 112, Pediculus capitis, the
head louse; Fig. 113, P. vestimenti, the body louse) with the young
bed-bug as figured by Westwood (Modern Classification of Insects, ii,.p.
475) we shall see a very close resemblance, the head of the young Cimex
being proportionally larger than in the adult, while the thorax is
smaller, and the abdomen is more ovate, less rounded; moreover the body
is white and partially transparent.

[Illustration: 113. Body Louse.]

[Illustration: 112. Head Louse.]

Under a high power of the microscope specimens treated with diluted
potash show that the mandibles and maxillae arise near each other in the
middle of the head opposite the eyes, their bases slightly diverging.
Thence they converge to the mouth, over which they meet, and beyond are
free, being hollow, thin bands of chitine, meeting like the maxillae, or
tongue, of butterflies to form a hollow tube for suction. The mandibles
each suddenly end in a curved, slender filament, which is probably used
as a tactile organ to explore the best sites in the flesh of their
victim for drawing blood. On the other hand the maxillae, which are much
narrower than the mandibles, become rounded towards the end, bristle
like, and tipped with numerous exceedingly fine barbs, by which the bug
anchors itself in the flesh, while the blood is pumped through the
mandibles. The base of the large, tubular labium, or beak, which
ensheathes the mandibles and maxillae, is opposite the end of the clypeus
or front edge of the upper side of the head, and at a distance beyond
the mouth equal to the breadth of the labium itself. The labium, which
is divided into three joints, becomes flattened towards the tip, which
is square, and ends in two thin membranous lobes, probably endowed with
a slight sense of touch. On comparing these parts with those of the
louse, it will be seen how much alike they are with the exception of the
labium, a very variable organ in the Hemiptera. From the long sucker of
the Pedicul