"No," said Mr. George, "at least the mulberry silk worms will not. There are a great many different kinds of silk worms in the world; that is, there are a great many different kinds of caterpillars that spin a thread and make a ball to wrap up their eggs in, and each one lives on a different plant or tree. If you watch the caterpillars in a garden, you will see that each kind lives on some particular leaf, and will not touch any other."
"Yes," said Rollo, "we found a big caterpillar once on the caraway in our garden, and we shut him up in a box, in order to see what sort of a butterfly he would turn into, and we gave him different kinds of leaves to eat, but he would not eat any but caraway leaves."
"And what became of him at last?" asked Mr. George.
"O, he turned into a butterfly," said Rollo. "First he turned into a chrysalis, and then he turned into a butterfly."
"There are a great many different kinds of silk worms," said Mr. George; "but in order to find one that can be made useful, there are several conditions to be fulfilled."
"What do you mean by conditions to be fulfilled?" asked Rollo.
"Why, I mean that there are several things necessary, in order that the silk worm should be a good one to make silk from. In the first place, the fibre of the silk that he spins must be fine, and also strong. In the next place, it must easily unwind from the cocoon. Then the animal must be a tolerably hardy one, so as to be easily raised in great numbers. Then the plant or tree that it feeds upon must be a thrifty and hardy one, and easily cultivated. The mulberry silk worm has been found to answer to these conditions better than any hitherto known; but there are some others that I believe they are now trying, in order to see if they will not be better still. They are looking about in all parts of the world to see what they can find."
"Who are looking?" asked Rollo.
"The Society of Acclimatation," replied Mr. George. "That is a society founded in Paris, and extending to all parts of the world, that is employed in finding new plants and new animals that can be made useful to man, or finding some that are useful to man in one country, and so introducing them into other countries. They are trying specially to find new silk worms."
"There are some kinds of caterpillars in America," said Rollo, "that wind their silk up into balls. I mean to get some of the balls when I go home, and see if I can unwind them."