Uncle George had to go from home for a week, and his two nephews went
part of the way to the railway station with him.
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.
“No, mother! he must come at once,” said the excited Frank. “There’s a
butterfly just coming out.”
“Oh, I must come and see that,” said Uncle George; and he allowed his
eager nephews to drag him towards the larva cage.
By the time they got to the cage the butterfly had hatched, but they
were in time to see it unfurl its wings. The wings were crumpled and
twisted, but the creature slowly straightened them out to dry in the
sun.
“We saw it burst its case,” said Tom. “First a small slit appeared at
the head end. This slit grew larger. Then the butterfly’s head and feet
appeared. It squeezed its way and was just half way out, with its wings
crumpled round it, when you arrived.”
“I arrived just a minute too late, then,” said his uncle.
[Illustration: White or Cabbage Butterfly and Pupa.]
“Oh, and the eggs have hatched too,” said Tom. “Look at them now, Uncle
George!”
His uncle looked, and saw that the white patches of eggs had given place
to larger patches of little active, dark coloured maggots.
“We want to know what has become of the lovely carved shells of the
eggs,” said Tom.
“They have been eaten up,” his uncle replied. “From the moment a
caterpillar is born he does nothing but eat—eat—eat. He begins by eating
the shell of the egg he comes out of.
“For the first week of their lives these tiny caterpillars feed together
in small bands, and they grow so fast you can almost fancy you see them
growing. After they have grown to a certain size, each caterpillar
starts out for himself.”
“Do you see the three butterflies that have hatched out?” asked Tom.
“Yes, I see them. There are two females and one male,” said Uncle
George.
“How can you tell males from females?” asked Frank.
“Oh, that is easy enough,” Uncle George replied. “The females are
larger, and have two big black spots on each of their front wings. But I
only see eight of the large cabbage caterpillars. We put in twelve, I
think.”
“Look!” said Frank, pointing to the roof of the cage.
“Ah, yes, I see them. Two of them have passed into the pupæ stage, and
are slung up by their silken belts to the wall of the cage.
“The other two are spinning silken belts round the middle of their
bodies, if they have not already done so. After this belt is finished
they will slowly slip their useless green skins off, and finally get rid
of them by sharply jerking the tail end of their pupa cases.”
“Yes, we watched those other two do that,” said Tom.
“Notice,” continued Uncle George, “that all your big cabbage
caterpillars have lost their yellow stripes and are now of a bluish
green colour. They have stopped feeding, and are now dull and sleepy.
This indicates that they are about to enter the pupa stage.”
“But look at the currant and the hairy caterpillars, uncle,” said Frank.
“My dear boy,” said Frank’s mother, “Uncle George must really have food
and rest after his long journey. He will hear about the other
caterpillars some other time.”
Exercises on Lesson XIII.
1. Explain why the pupæ of white butterflies are coloured like the
objects they are attached to.
2. Write the life of a white butterfly, and illustrate your
description with sketches of caterpillar, pupa, and butterfly.
3. The life of an insect is divided into four distinct stages. Name
them. Which is the longest stage in the case of the white
butterfly?
4. Describe, as you have observed it, the behaviour of a caterpillar
as it passes from the larva to the chrysalis form.