for
walking, but is carried straight forwards, so that the inner surfaces of
its joints are close to the outer surface of the jaw. Now, whenever the
'palp' is moved, it is rubbed against the 'teeth' in the jaw, and this
consequently, in many spiders, produces a sound like the humming of a
bee! In some spiders which have this apparatus, the sound produced
cannot be heard by human ears.

It is to be noted that, whatever the sound produced, its purpose is to
serve one of two very different ends. It may be used, as in some
spiders, when it is found only in the males, to charm its mate in
courting; for she has a very bad temper, and must be approached most
cautiously. But in the case of the huge bird-eating spiders, this
curious buzzing sound appears to be made for the purpose of frightening
its enemies, which, connecting the buzzing sound with the power of
stinging, give the spider a wide berth as soon as the buzzing begins! To
make itself appear more terrible, the spider raises the fore part of the
body and legs high in the air, and thus, partly by this threatening
attitude, and partly by the sound, persuades those about to attack that
'discretion is the better part of valour!'

The scorpion hisses. Some describe the noise as like that produced by
rubbing the finger-nail over the hairs of a stiff tooth-brush. The
vibrating instruments are found in different places, according to the
species of scorpion. But the plan of its construction is the same in
all, and is like that of the spider. Thus, in some species (as in fig.
4) there are, at the outer side of the base of the great pair of
pincers, a number of sharp spinelets, shaped like a tiger's 'fang.'
These make up the 'scraper.' Against it the scorpion rubs a number of
tubercles, or little rounded bodies, which are seated on the base of the
first pair of walking-legs; these form the 'rasp.' The movement of the
rasp on the scraper produces the hissing sound. Sometimes the hissing is
produced by a similar rasp and scraper placed on the inner surface of
the little pincers which project in front of the body, between the two
great pincers. In other cases the rasp and scraper are found, the rasp
on the top of the base of the little pincer, the scraper on the under
surface of the overhanging shield of the body. But, however formed, the
noise produced is similar, and appears to be meant to terrify enemies.
This purpose is further aided by the habit the creature has, when angry,
o