with the
mites, are true insects, as they are born with only three pairs of feet,
as are the mites and ticks, and breathe by tracheae; and thus a common
plan of structure underlies the entire class of insects.

[Illustration: 179. Young Pauropus.]

[Illustration: 180. Spring-tail.]

[Illustration: 181. Young Julus.]

A very strange Myriopod has been discovered by Sir John Lubbock in
Europe, and we have been fortunate enough to find a species in this
country. It is the Pauropus. It consists, when fully grown, of nine
segments, exclusive of the head, bearing nine pairs of feet. The young
of Pauropus (Fig. 179) is born with three pairs of feet, and in its
general appearance reminds us of a spring-tail (Fig. 180) as may be seen
by a glance at the cut. This six-legged form of Pauropus may also be
compared with the young galley worm (Fig. 181).

[Illustration: 182. Leptus.]

[Illustration: 183. Tardigrade.]

Passing to the group of spiders and mites, we find that the young mites
when first hatched have but three pairs of feet, while their parents
have four, like the spiders. Figure 182 represents the larva (Leptus)
of the red garden mites; while a figure of the "water bear," or
Tardigrade (Fig. 183), is introduced to compare with it, as it bears a
resemblance to the young of the mites, though their young are born with
their full complement of legs, an exception to their nearest allies, the
true mites. Now if we compare these early stages of mites and myriopods
with those of the true six-footed insects, as in the larval Meloe,
Cicada, Thrips and Dragon fly, we shall see quite plainly that they all
share a common form. What does this mean? To the systematist who
concerns himself with the classification of the myriads of different
insects now living, it is a relief to find that all can be reduced to
the comparatively simple forms sketched above. It is to him a proof of
the unity of organization pervading the world of insects. He sees how
nature, seizing upon this archetypal form has, by simple modifications
of parts here and there, by the addition of wings and other organs
wanting in these simple creatures, rung numberless changes in this
elemental form. And starting from the simplest kinds, such as the
Poduras, Spiders, Grasshoppers and May flies, allied creatures which we
now know were the first to appear in the earlier geologic ages, we rise
to the highest, the bees with their complex forms, their diversified
economy