86 CERTAIN PARASITIC INSECTS. 
ond,” is a nonentity.  Schiódte, in his essay "On Phthirius, 
and on the Structure of the Mouth in Pediculus” (Annals 
and Magazine of Natural History, 1866, page 213 ), says 
that these statements will not bear examination, and that this 
disease should be placed on the “retired list,” for such a 
malady is impossible to be produced by simply blood-sucking 
animals, and that they are only the disgusting attendants on 
other diseases. Our author thus describes the mouth parts 
of the louse. 
“Lice are no doubt to be regarded as bugs, simplified in structure and 
owere 
sites, small, flattened, apterous, myopic, crawling and climbing, with a 
conical head, moulded as it were to suit the rugosities of the surface they 
inhabit, provided with a soft, transversely furrowed skin, probably en- 
dowed with an acute sense of feeling, which can guide them in that twi- 
light in which their mode of life places them. The peculiar attenuation 
of the head in front of the antenns at once suggests to the practised eye 
the existence of a mouth adapted for suction. This mouth differs from 
that of Rhynchota [Hemiptera, bed-bug, etc.] generally in the circum- 
stance that.the labium is capable of being retracted into the upper part 
of the head, which therefore presents a little fold, which is extended 
when the labium is protruded. In order to strengthen this part, a flat. 
band of chitine is placed on the under surface, just as the shoemaker puts 
a small piece of gutta-percha into the back of an India-rubber Shoe; as, 
however, the chitine is not very elastic, this band is rather thinner in the 
degree of protrusion; if this is at its highest point the orifice is turned 
inside out, like a collar, whereby the small hooks are directed backwards, 
so that they can serve as barbs. These are the movements which the 
g 
ium, and along the walls of this tube the setiform mandibles and maxille 
in the shape of long narrow bands of chitine. In this way the tube of 
