2. There is a little worm which is called xylophthorus,[187] which is no less extraordinary than these animals; for its variegated head is projected beyond its case, and its feet are at the extremity, as in other worms. The rest of the body is contained in a case made of a substance like spider's web, and a dry material on the outside of this; so that it appears to walk about with this attached to it. These creatures are attached to their case, and as a snail to its shell, so the whole of the case is joined to the worm, and it does not fall out of it, but is drawn out of it, as if they were joined together. If a person pulls off the case, the creature dies, and becomes as helpless as a snail without its shell. As time advances, this grub becomes a chrysalis, like a caterpillar, and lies without motion: but the nature of the winged creature that is produced has never been ascertained. [187] Tinea graminella, Tinea lichenella, Tinea Xylophorus, or perhaps larva of Phryganea. 3. The wild figs upon the fig-trees contain a creature called psen;[188] this is at first a little worm, and afterwards having ruptured the case, the psen flies out, and leaves it behind. It then pierces the unripe figs, and causes them not to fall off, wherefore gardeners place wild fruit near the cultivated kinds, and plant the wild and cultivated plants near each other. [188] Cynips Psenes. CHAPTER XXVII. 1. The sexual intercourse of sanguineous and oviparous quadrupeds takes place in the spring. They do not, however, all copulate at the same season; but some in the spring, others in the summer or autumn, as the season is appropriate for bringing up the young of each species. The tortoise produces hard, two-coloured eggs, like those of birds. Having deposited her eggs, she buries them, and makes a beaten place above them. When this is done, she sits upon them. The eggs are hatched the following year. The emys goes out of the water to deposit her eggs, and digs a hole like a cask, in which she places her eggs and leaves them. Having left them alone for less than thirty days, she digs them up again and hatches them and leads them at once to the water. The marine turtles deposit their eggs in the earth like domestic birds, and cover them up with earth and sit upon them during the night. They produce a great many eggs, as many as an hundred. 2. The saurians and both the land and river crocodiles produce their eggs upon the land. Those of the lizards are hatched spontaneously in the earth; for the lizard does not live a whole year, for it is said to live only six months. The river crocodile produces as many as sixty eggs, which are white. She sits upon them for sixty days, for they live a long while. A very large animal is produced from these small eggs; for the egg is not larger than that of a goose, and the young is in proportion, but when full grown the creature measures seventeen cubits. Some persons say that it grows as long as it lives. CHAPTER XXVIII.