Elementary Zoology, Second EditionKellogg, Vernon L. (Vernon Lyman)
Science
Elementary Zoology, Second Edition
Kellogg, Vernon L. (Vernon Lyman)
Animals; Zoology
TECHNICAL NOTE.--From under stones or logs obtain specimens of
millipeds, or thousand-legged worms (large blackish, cylindrical,
worm-like animals with each body-segment back of the fourth bearing
two pairs of jointed legs); also specimens of centipeds or
hundred-legged worms (flattened, usually brownish or pale worm-like
animals with the body-segments bearing only one pair of legs each)
in the same places. Examine the external structure; note number of
body-rings; division into body-regions; presence of antennæ;
character and number of eyes; character of mouth-parts; character
and arrangement of legs. In the centipeds the first pair of legs is
modified to form a pair of poison-fangs. They appear to belong to
the mouth-parts. The internal anatomy will be found to be, if
examined, much like that of insects and can be studied from the
account of the anatomy of the water-scavenger beetle and butterfly
larva. Compare the Myriapods with the Hexapods or true insects. What
are the points of resemblance? what are the points of difference?
The Myriapoda are land-animals breathing by means of tracheæ like the
insects. In them the body-segments are nearly uniform in character with
the exception of the head, which, as in the insects, bears the
mouth-parts and antennæ. There is no grouping of the body-segments into
regions except as the head is opposed to the rest of the body. (In a few
myriapods there are indications of a division of the hind body into
thorax and abdomen.) The presence of true legs on all the segments of
the hinder region of the body and the lack of the three-region division
of the body are the principal external structural characteristics which
distinguish myriapods from insects. The internal anatomy corresponds in
general character with that of insects.
[Illustration: FIG. 86.--A galley-worm (milliped), _Julus_ sp. (From
specimen.)]
The most familiar myriapods are the millipeds, and the lithobians and
centipeds. The millipeds are cylindrical in shape, have two pairs of
legs on most of the body-segments and are vegetable feeders, though
some may feed on dead animal matter. The galley-worms (_Julus_) (fig.
86), large, blackish, cylindrical millipeds found under stones and
logs and leaves and in loose soil, are familiar forms. They crawl
slowly and when disturbed curl up and emit a malodorous fluid. They
can easily be kept alive in shallow glass vessels with a layer of
earth in the bottom, and their habits and life-history may thus be
studied. They should be fed sliced apples, green leaves, grass,
strawberries, fresh ears of corn, etc. They are not poisonous and may
be handled with impunity. They lay their eggs in little spherical
cells or nests in the ground. An English species of which the
life-history has been studied lays from 60 to 100 eggs at a time. The
eggs of this species hatch in about twelve days.
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