“Each of these darker coloured cases contains a white butterfly. They have been here all winter, and they are just about to hatch out.”
“How do you know that, Uncle George?”
“I know it because the empty cases tell me that some of the butterflies have just hatched out. This is what your cabbage caterpillar becomes after he is tired of feeding.
“You have now seen three different stages of the life of this insect. First, the curious eggs laid on the under side of the cabbage leaf; next the greedy caterpillar; and now, the chrysalis or pupa stage.
“The caterpillar goes to sleep in autumn as a hard-cased chrysalis, and wakes up in spring a beautiful butterfly.”
“How strange,” said Frank. “And will our caterpillars remain caterpillars until autumn, and then tuck themselves up like this and go to sleep for the winter.”
“No, Frank! our caterpillars will go into the chrysalis state in a week or so, and hatch out as butterflies in August. These August butterflies will lay eggs. The caterpillars from these eggs will turn into pupæ in September.
“These September pupæ will supply the white butterflies of next spring and summer. Put some of these into your box. Watch then carefully, and you may be lucky enough to see the white butterfly coming out of his winter case.”
“I cannot understand,” said Tom, “how a big white butterfly can be inside so small a case. It must be very tightly wrapped up.”
“So it is, as you will see,” said Uncle George. “Good-bye, boys! and mind, when I come back, I shall expect to see notes and sketches of all that has taken place in the larva cage during my absence.”