One of the great divisions into which the insects are divided relates to their possession of six legs (Fig. 180). This includes a marvelous array of creatures. Among them we find the singular little glacier flea (Fig. 181) and the springtail, a prodigious jumper (Fig. 182). The latter is found in damp places, and when touched will release a forked spring which is held in place by a hook, and this sends the insect flying into the air like an acrobat. These humble little creatures present a strange contrast to the lace-winged insects which are among the most beautiful of the tribe.

The May flies (Fig. 183) are well known for the wonderful exhibitions they sometimes make, the air being filled with them, a joyous, beautiful throng, destined to live but a few hours. In South America they occur in such vast numbers that they are collected and used as guano. The young pass through a strange change, having little resemblance to the parent, and live in the water, where they breathe by means of several plumelike gills.

Among all the insects of the field and swamp none are more familiar than the dragon fly (Fig. 184), which children were once led to believe had a vicious habit of sewing up the eyes and mouth of any one; hence the name "darning needle." These insects are often beautiful, with their rich wings of glistening lace, four in number, their bodies gleaming in tints of bronze, blue, and black. The abdomen is long and slender, like a needle; the head is prominent and armed with powerful jaws; the eyes are large and compound, with several single eyes as well. Some dragon flies are very small. Others are large, as those of the Malay Archipelago, where the natives trap them and use them for food. The dragon flies are hunters, preying upon other insects which they capture on the wing, and large forms have been seen taking very young fishes from the water, swooping down upon them like hawks.

The development of the dragon fly is interesting from the fact that the young lives a long period in the water. The eggs are deposited in the water, hatching out into curiously shaped creatures (Fig. 185), which are among the most ferocious of all the water insects. They pass two years in this form, preying upon other animals and even small fishes. The larva has a proboscis which ordinarily folds over the face and is called the mask (B), but when an insect approaches, this strange appliance with powerful jaws or hooks is shot out (A) with dire results. After the two years have passed the pupa, as it is called, climbs up a stem, leaves the water and casts its skin, appearing as a full-grown dragon fly ready for a life of rapine on land.

In many insects the habits of the young are much more interesting than those of the adults. Not far from my home, in the Arroyo Seco, which leads down from the Sierra Madre, are great deposits or beds of fine sand which I find often covered with little pits (Fig. 186). If a section is made (Fig. 187), it is found to be a perfect bowl almost half an inch in depth, as though a top had been pressed into the sand and taken out. If sand is rolled into the pit, something appears quickly at the bottom and mysteriously tosses it out; and if an ant topples over the edge and rolls down the sides, out comes a fierce pair of jaws and seizes it. If the ant escapes, the unknown creature, still concealed, hurls sand at it, endeavoring to bring it down, often with success. This singular creature is the larva or immature young of the ant lion—itself an attractive, large, lace-winged creature (Fig. 188), resembling a dragon fly. It lays its eggs in dry places. The young are wingless, big-jawed creatures, which for two years live the life of a trapper, each forming a pit and concealing itself beneath the sand at the bottom, the huge jaws being in the center. Ants are the game of this lion, and as they run along they often topple over the sides which, like those of a toboggan, are very slippery. Down the ant goes, its descent being accelerated by the lion which places sand upon its back, and bombards the unfortunate, so adding to its confusion that it rolls down and is seized by the jaws of the lion. At the end of the two years the lion surrounds itself with a ball of sand and silk, and in three weeks appears as the perfect insect.

Unless one is familiar with the eggs of the aphis lion (Fig. 189) he will never find them. They resemble minute plants growing on long stems, fastened to a leaf. These hatch out and become little creatures resembling the ant lion, with huge jaws.

But the most extraordinary changes and series of different individuals are found among the so-called white ants, which are really not ants at all, but among the most destructive of all known insects. The first white travelers in Africa reported the discovery of gigantic ant hills, some of which were twelve feet in height (Fig. 190) and one hundred feet in circumference. Equally large mounds have been found in Australia, large areas of country being dotted with these striking landmarks, among the most remarkable of all animal structures. These mounds are often as hard as rock, and hunters have sometimes escaped from the charges of wild animals by climbing upon them.

They are the work of the so-called white ants. A section made through one of them, as seen in the illustration, shows the singular home of a remarkable community. There are really four kinds of "ants" here, all representing a different phase in the growth of the insect, and all performing a certain work. They are the female, the male, the worker, and the soldier; and there is a winged king. In their lives these insects have many features which resemble those of man. They have a king and queen, which at first have wings; later they lose their wings and the queen grows until she is thousands of times larger than the workers, and is kept in a special chamber in the center of the pile. Here she is attended by the workers, small ants, who carry out the eggs which are laid by millions and placed in nurseries or small cemented cells, designed for the purpose. Sometimes the queen lays as many as eight thousand eggs a day. An army of workers carries them off, builds new nurseries, and adds to the heap. If an enemy appears, the soldiers rush out. These have large heads and enormous jaws, and are well fitted by nature for the work they have to perform.

The cunning and intelligence of white ants are well displayed in their attacks upon houses. Having decided to enter a house, they begin to tunnel some distance away, and finally reach the corner post or some timber that enters the ground. With remarkable speed the workers enter this, hollowing it out, until it is nothing but a shell. They eat to the very surface, leaving only a faint ghost of a partition, and what appears to be a solid block is really so thin that a finger can be thrust through it. So clever are these little ant miners that they have been known to come up through the floor directly beneath the leg of a chair, and burrow and eat up through it, so completely devastating it that when the owner moved it the small hole in the floor appeared and the chair fell in pieces.

In the Isle of France a new building was ruined by these insects in a few months; and at Colombo a large house suddenly fell in over the heads of the occupants, the beams being crushed like egg shells. The work they accomplished in this way would hardly be credited were it not for the substantiated statements collected by the authorities in the countries where they are mostly found.

The so-called caddis worms (Fig. 191) are merely the larvÆ of the caddis fly which incloses itself in a case that is often decorated in a singular way. The cases of a number of the worms placed together display a striking variety of designs. Some roll up leaves; others spin a silken thread from the mouth and bind pieces of leaves together, attaching other pieces to it.