These creatures are active in their motions, and rapacious in their habits. Some of them feed on small insects, others attack earthworms. Their bite is venomous to insects, and one species having very long legs will produce by its bite a severe pain lasting several hours. A large species found in the Southern States, and in the tropics, and commonly known

FIG. 117.-SHOWING MAGNIFIED VIEW OF Tthe Under SuRFACE OF THE HEAD OF A CENTIPEDE: a, Antenna; m p, Maxillary Palpus; fj, Foot-jaw; f, Poison-Fang of Foot-jaw; 7, Labium; m, Maxilla. The Mandibles are hidden behind the other parts, and do not show.

as the centipede, is considered a dangerous animal from its bite. The feet of this species are supposed to poison by their touch, since, when they run over the flesh, small ulcers appear where the feet have come in contact with the skin. The pupils may collect these animals, and either dry them and stick them to cards, or preserve the specimens in vials filled with alcohol.

116. The other group of myriapods, commonly known as

millepedes, have a long, cylindrical, and oftentimes shiny body, composed of a great many segments so smoothly joined together that it is difficult to see the separation between them.

The antennæ are short, there are no long caudal appendages, and the legs are short and feeble. At first sight it would appear that these creatures were exceptional among insects and spiders, in having two pairs of legs to one segment; but it has been learned, by studying the very young millepede, that there is really but one pair of legs to a segment, but that the segments grow together in pairs, so that each apparent segment is really two segments united.

FIG. 118. A COMMON MILLEPEDE. The line underneath the figure represents the length of the specimen from which the drawing was made. A, a Magnified View of the Head of the Millepede represented above; B, a Magnified View of the Left Jaw.

These creatures live on decaying matter, and are slow and weak in all their movements. When touched, or alarmed, they coil up in a closely-wound roll. The body is hard, and the animal can be stuck on a card for the cabinet. The eggs, to the number of sixty or more, are laid in little burrows

previously prepared by the creature in earth that is neither too moist nor yet too dry. In preparing the burrow the female makes use of the fluid which comes from her mouth, and which enables her to stick the earth together in little balls, and these she passes up from her burrow by means of the little legs which grasp the pellet and convey it from one pair of legs to the next pair, and so on till it is thrown out of the burrow. After the burrow is completed, and the eggs laid, the entrance to the nest is carefully filled up with clay, or dirt, moistened with fluid from the mouth.

117. It has been learned, in studying the development of the insect proper, that the worm-like larva comes from the egg with its full number of rings or segments, and that, as the creature matures, some of these segments are so merged into other parts, particularly with some of the caudal ones, that it seems as if the perfect insect has a less number of rings than the larva. In the myriapods, however, the young creature as it hatches from the egg possesses only a few seg

FIG. 119.-HIGHLY-MAGNIFIED FIGURE OF A VERY YOUNG MILLEPEDE, SHORTLY AFTER HATCHING FROM THE EGG.

(Reduced from a figure by Elias Metschnikoff.)

ments, but as it grows, new segments are from time to time formed near the hinder part of the body, until the creature

attains adult size, when it may possess over a hundred seg

ments.

Like true insects, however, the young myriapod makes its appearance from the egg with three pairs of legs. The body, however, is never divided into a thoracic portion, and an abdominal portion, as in the true insects, or into two regions as in the spiders, but after the head there succeeds a continuous row of similar segments to the tail.

118. In studying the insects, spiders, and centipedes, or myriopods, the pupils have learned something about three groups of animals which have in common a body composed of segments, and possessing jointed legs. They all breathe air through holes in the side of the body, called spiracles, the air, thus breathed, finding its way through various parts of the body by means of little tubes called tracheæ, except in the spiders, where little sacs, called pulmonary sacs, take the place of tracheæ.

In the true insects the segments of the body are gathered into three regions, called respectively the head, thorax, and abdomen. In the spiders the segments of the body are gathered into two regions, called respectively the cephalo-thorax, and abdomen, the head being merged in the thorax. In the myriapods the head is again distinct as in the true insects, but the remaining segments of the body are distinct and are not grouped into regions.

The true insects have three pairs of legs. The spiders have four pairs of legs, while the myriapods have no definite number of legs. In some species there are nearly two hundred

pairs of legs, and in no species are there less than ten pairs of legs. The true insects alone have wings.

119. In the growth or development of the true insects and spiders, the young animal comes from the egg with its full number of segments complete, while in the myriapods the young animal comes from the egg with a few segments, and new ones are added as the animal grows.

Some of the characters of the insects, spiders, and myriapods, may be represented as follows:

SPIDER.--Body divided into Two Regions, Head not separate.

No definite number of legs

MYRIOPOD.-Body not divided into Regions, but Head separate.

FIG. 120.-ANIMALS WHOSE BODIES ARE COMPOSED OF SEGMENTS POSSESSING JOINTED LEGS, AND BREATHING AIR THROUGH OPENINGS IN THE SIDES OF THE BODY.

On account of some of these characteristics above mentioned, with others not mentioned, being held in common by the true insects, spiders, and myriapods, these creatures form a natural. group in the animal kingdom, just as the snails,

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