Part 17

As they were about to take a short cut through the wood, Uncle George went up to a huge beech tree. He looked very closely at its grey trunk for a time, then stepping back from it about three yards, exclaimed:—

“Come here boys! Stand beside me, look closely at this tree, and tell me if you see any strange objects sticking to the bark.”

After staring at it for some time, they both declared that they could see nothing upon it.

“Go nearer—nearer still! Now, do you see anything?”

The boys shook their heads.

“Go quite close up to the trunk and examine it,” said Uncle George.

“Oh,” said Frank suddenly, “I see queer things like grubs, coloured almost exactly like the bark. Some of them are lighter in colour.”

“Look carefully at those lighter ones, and you will find that they are just empty cases.”

“So they are,” said Frank, as he touched one with his finger and saw it crush up.

“Notice how they are fixed to the bark!” said Uncle George.

The boys watched as their uncle placed his pencil under one of the darker coloured objects, and saw that it was slung up to the tree by a loose silken girdle round its middle, while a tuft of fine threads fastened the lower end to the bark.

Suddenly, as if it were annoyed at being touched by the pencil, the lower half of the object moved from side to side with rapid jerks.

“Why, it is alive,” said Tom.

“Yes, of course it is,” said his uncle. “This is another lucky find.”

“What are they?” Frank asked.

“Can’t you guess, Frank? Don’t you remember my telling you that all the insects were asleep in their cases during winter.

“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.”

* * * * * * * *

“Won’t you let your uncle take his dinner first,” said Frank’s mother, as she hung Uncle George’s overcoat up in the hall.