by the parent if not protected by the workers. If the young queen survive, the old queen departs with many of her subjects, and collects them into a dense swarm attached to a limb of a tree, where they remain until scouts return to conduct them to their new home.

127. The wasps.-The digger-wasps are frequently to be seen gnawing tunnels in the wood or earth, at the inner end

of which an egg is laid. In some species the developing young is nourished by food carried in to it day by day. In other cases the parent may never see her child, dying or abandoning it before its birth; but before departing she is careful to place within reach a sufficient supply of spiders, caterpillars, beetles, or locusts that shall nourish the little one until it becomes a motionless pupa. This stage is soon over, and the adult wasp now digs its way to the surface. Passing by the familiar mud-wasps or mud-daubers, whose nests are common objects under stones or against

the rafters of barns and houses, we arrive at the social wasps. As the name indicates, these insects, such as the yellow-jackets and hornets, live together in companies which consist, as in the ants and bees, of males, females, and workers. They also are fond of the juices of fruits, and many of them destroy insects which may be fed to the young. Their nests are variously situated and constructed, but all of them agree in being composed, at least in part, of a grayish substance which is in reality a kind of paper. With their jaws they scrape off from old logs and fences small particles of wood, which they probably mix with saliva, and rolling the mass into a ball set out for home. These pellets are then flattened out into thin sheets, and worked up into hexagonal cells, in which the eggs are laid.

Along with the nests of the mud-daubers one frequently notices the nests of some of the familiar wasps (Polistes), which build cake-like nests composed of thirty or forty hexagonal cells attached by a stalk. Somewhat similar nests, though usually more extensive, are constructed by the yellow-jackets in cavities in the ground. The numerous combs of the hornet are surrounded by several sheets of wood-pulp, and the whole structure is attached generally to the limb of a tree.

In the spring the nests of all these species of wasps are commenced by a single female, who has lived in a dormant condition through the winter. She builds a small nest and in time is surrounded by numerous workers, which live in perfect harmony, enlarging the nest and rearing the young. As autumn approaches the young males and females leave the nest; but the males, together with the workers, all succumb to the cold, and none but the females persist to found a new colony the following spring.

CHAPTER XI

ARTHROPODS (Continued). CLASS ARACHNIDA

128. General characters. In this group, comprising the spiders, mites, and a large assemblage of related species, we again meet with great differences in form and structure which fit them for lives under widely different conditions. The three regions of the body, head, thorax, and abdomen, so clearly marked in the insects, are here less plainly defined. The head and thorax are usually closely united, and in the mites the boundaries of the abdomen are also indistinct. The appendages of the head are two in number, and probably correspond to the antennæ and mandibles of other Arthropods. In the scorpions and some species of mites these are furnished with pincers for holding the prey, and in other forms they act as piercing organs. Usually the thorax bears four pairs of legs, a characteristic which readily separates such animals from the insects.

The internal organization differs almost as much as does the external. In many species it shows a considerable resemblance to that of some insects, but in others, especially those of parasitic habits, it departs widely from such a type. Respiration is affected by means of trachea, or lung-books, which consist of sacs containing many blood-filled, leaf-like plates placed together like the leaves of a book.

Usually, as in the insects, the young hatch from eggs which are laid, but in the scorpions and some of the mites the young develop within the body and at birth resemble the parent. Almost all of these organisms live either as

parasites or as active predaceous animals upon other animals. For this purpose many are provided with keen senses for detecting their prey and poisonous spines for despatching it.

129. The scorpions.-Owing to the stout investing armor, the strong pincers, and the general form of the body, the scorpions might at first sight be mistaken for near relatives

of the crayfish or lobster. A more careful examination will show that the two pairs of pincers probably correspond to the antennæ and mandibles of the Crustacea that have become modified for seizing the food. The swollen part of the animal lying behind the four pairs of legs is a part of the abdomen, of which the slender "tail" constitutes the remainder. On the tip of the tail is a curved spine supplied with poison glands. Several pairs of eyes are borne on the dorsal surface of the head and thorax, while on the under side of the animal several slit-like openings lead into as many small cavities containing the lung-books.

FIG. 82.-Scorpion, showing pincer-like mouthparts and spine-tipped tail.

The scorpions are the inhabitants of warm countries, where they may be found under sticks and stones throughout the day. At night they leave their homes in search of food, which consists chiefly of insects and spiders. These are seized by means of the pincers, and the sting is driven. into them with speedily fatal results. It is doubtful if the poison causes death in man, but the sting of some of the

larger species, which measure five or six inches in length, may produce certain disorders chiefly affecting the circulation. In this country there are upward of thirty species, most of which are comparatively small.

130. The harvestmen.-The harvestmen or daddy-longlegs are small-bodied, long-legged creatures which resemble in general appearance several of the spiders. They differ from them, however, in the possession of claws corresponding to the smaller ones of the scorpion, and in their method of respiration, which is similar to that of insects. During the day they conceal themselves in dark crevices or stride slowly about in shaded places; but at night they emerge into more open districts and capture small insects, from which they suck the juices.

131. The spiders.-The spiders are world-wide in their distribution, and are a highly interesting group, owing chiefly to their peculiar habits. Examining any of our familiar species, it will be seen that the united head and thorax are separated by a narrow stalk from the usually distended abdomen. To the under side of the former are attached four pairs of long legs, a pair of feelers, and the powerful jaws supplied with poison-sacs, while eight shining eyes are borne on the top of the head. On the abdomen, behind the last pair of legs, are small openings into the lung cavities which contain a number of vascular, leaflike projections known as lung-books. In some species a well-marked system of trachea are also present. At the hinder end of the body are four or six little projections, the spinnerets, each of which is perforated with many holes. Through these the secretion from the glands beneath is squeezed out in the form of excessively delicate threads, often several hundred in number, which harden on exposure to the air. According to the use for which these are intended, they may remain a tangled mass or become united into one firm thread; and according to the habits of the animal, they may be used for enclosing their eggs,