cavity in the earth, perhaps two by three feet in diameter and a foot beneath the surface, walled with a thick cernent lining; but from this charnber there rnay extend tunnels upward to the surface, or horizontally to other smaller charnbers located at a distance from the central one. The termites that lire in these nests subsist principally upon horne-grown food, and it is in the great vaulted central charnber that they raise the staple article of their diet. The cavity is filled almost entirely with a porous, spongy rnass of living fungus. The fungi as we ordinarily see them are the toadstools and rnushrooms, but these fungus forms are merely the fruiting bodies sent up from a part of the plant concealed beneath the ground or in the dead wood; and this hidden part has the form of a network of fine, branching threads, called a OEycelium. The rnyceliurn lires on decaying wood, and it is the rnycelial part of the fungus that the termites cultivate. They feed on srnall spore-bearing stalks that sprout from the threads of the rnyceliurn. The substraturn of the termite fungus beds is generally made of pellets of partly digested wood pulp. The nests that termites erect above the ground include the most rernarkable architectural structures produced by insects. They are round in South America, Australia, and particularly in Africa. In size they vary from rnere turrets a few inches high to great edifices six, twelve, or even twenty feet in altitude. Sorne are simple rnounds (Fig. 86 A), or rnere hillocks; others have the form of towers, obelisks, and pyrarnids (B); still others look like fantastic cathedrals with buttressed walls and taper- ing spires (Fig. 87) ; while lastly, the strangest of all re- semble huge toadstools with thick cylindrical stalks and broad-brirnrned caps (Fig. 86 C). Many of the termites that build mound nests are also fungus-growing species, and one charnber or several chambers in the nest are given over to the fungus culture. Termite nests built in trees are usually outlying retreats
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TERMITES
