ng, which can guide
them in that twilight in which their mode of life places them. The
peculiar attenuation of the head in front of the antennae at once
suggests to the practised eye the existence of a mouth adapted for
suction. This mouth differs from that of the Hemiptera (bed-bug, etc.)
generally, in the circumstance 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 middle, in order that it may
bend and fold a little when the skin is not extended by the lower lip.
The latter consists, as usual, of two hard lateral pieces, of which the
fore ends are united by a membrane so that they form a tube, of which
the interior covering is a continuation of the elastic membrane in the
top of the head; inside its orifice there are a number of small hooks,
which assume different positions according to 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 animal executes after
having first inserted the labium through a sweat-pore. When the hooks
have got a firm hold, the first pair of setae (the real mandibles
transformed) are protruded; these are, towards their points, united by a
membrane so as to form a closed tube, from which, again, is inserted the
second pair of setae, or maxillae, which in the same manner are
transformed into a tube ending in four small lobes placed crosswise. It
follows that when the whole instrument is exserted, we perceive a long
membranous flexible tube hanging down from the labium, and along the
walls of this tube the setiform mandibles and maxillae in the shape of
long narrow bands of chitine. In this way the tube of suction can be
made longer or shorter as required, and easily adjusted to the thickness
of the skin in the particular place where the animal is sucking, whereby
access to the capillary system is secured at any part of the body. It is
apparent, from the whole structure of the instrument, that it is by no
means calculated on being used as a sting, but i