Flies and
bees and the like may be constantly seen thus dressing themselves with
crossed forelegs. Of the other legs, the hinder are bigger than the
middle pair, both to aid in running and also that the insect, when
it takes flight, may spring more easily from the ground. This
difference is still more marked in such insects as leap, in locusts
for instance, and in the various kinds of fleas. For these first
bend and then extend the legs, and, by doing so, are necessarily
shot up from the ground. It is only the. hind legs of locusts, and not
the front ones, that resemble the steering oars of a ship. For this
requires that the joint shall be deflected inwards, and such is
never the case with the anterior limbs. The whole number of legs,
including those used in leaping, is six in all these insects.
7
In the Testacea the body consists of but few parts, the reason being
that these animals live a stationary life. For such animals as move
much about must of necessity have more numerous parts than such as
remain quiet; for their activities are many, and the more
diversified the movements the greater the number of organs required to
effect them. Some species of Testacea are absolutely motionless, and
others not quite but nearly so. Nature, however, has provided them
with a protection in the hardness of the shell with which she has
invested their body.
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