One answer suggests itself inevitably, to begin with: the food problem, that terrible disturber of the world’s tranquillity, is here non-existent. Peace reigns as soon as the stomach is certain of being filled without a struggle. A pine-needle or even less suffices for the caterpillar’s meal; and that needle is always there, waiting to be eaten, is there in inexhaustible numbers, almost on the threshold of the home. When dinner-time arrives, we caterpillars go out, we take the air, we walk a little in procession; then, without laborious seeking, without jealous rivalries, we seat ourselves at the banquet. The table is plentifully spread and will never be bare, so large and generous is the pine; all that we need do is, from one evening to the next, to move our dining-room a little farther on. Consequently, there are no present and no future cares on the subject of provisions: the caterpillar finds food to eat almost as easily as he finds air to breathe. The atmosphere feeds all creatures on air with a bounty which it is not necessary to crave. All unknown to itself, without the agency of any effort or labour, the animal receives its share of the most vital of elements. The niggardly earth, on the contrary, surrenders its gifts only when laboriously forced. Not fruitful enough to satisfy every need, it leaves the division of the food to the fierce eagerness of competition. The mouthful to be procured engenders war between consumers. Look at two Ground-beetles coming at the same time upon a bit of Earth-worm. Which of the two shall have the morsel? The matter shall be decided by battle, desperate, ferocious battle. With these famished ones, who eat at long intervals and do not always eat their fill, communal life is out of the question. The Pine Caterpillar is free from these woes. He finds the earth as generous as the atmosphere; he finds eating as easy as breathing. Other instances of perfect communism might be named. All occur among species living on a vegetable diet, provided however that victuals are plentiful and obtainable without a hard search. An animal diet, on the contrary, a prey, always more or less difficult to secure, banishes cenobitism. Where the portion is too small for one, what excuse would there be for guests?