During summer the boys paid many visits to the horse pond. Each time
they went there they saw something to interest them.
Their uncle taught them to keep perfectly still while looking into the
water. They soon came to know that this was the best way to study
pond-life, for, whenever they moved, the creatures they were watching
would dart out of sight.
One day, while they were both lying on the bank gazing into the pond, a
huge black beetle came up to the surface of the water. It remained there
for a few moments, with its head hanging downwards and its tail sticking
right out of the water. Then it dived down out of sight. In a few
minutes it came up again, and this time Frank’s net was under it before
it could escape.
Just as Frank was putting it into the glass jar, Tom whispered, “Here is
another one—quick, Frank!”
But Frank was too late; for before he could get the first beetle into
the jar, the second one had dived to the bottom of the pond. The boys
waited for a long time, hoping to see the other beetle again. At last
their patience was rewarded. The beetle came up again to the surface. As
soon as it did so, in went the net, and out came beetle number two.
“What big beauties,” said Frank. “I wonder what they are. Let us hurry
home and show them to Uncle George.”
When they got home, their uncle placed the two beetles in a glass tank
by themselves, so that they could be more easily observed.
“What do you call them, uncle?” asked Frank. “We have never seen such
large, handsome beetles before.”
[Illustration: Dyticus Beetle, male and female.]
“Have you not?” his uncle replied. “I am surprised at that, for this
beetle is found in nearly all our ponds and ditches. It has a long Latin
name,[2] which means _Bordered Diver_, but it is commonly known as the
‘great water beetle.’ There are several kinds of these diving beetles.
This is the largest. Can you give me an idea of their size?”
And Uncle George handed Frank a small measuring rule which he carried in
his pocket.
Frank looked at the beetles, and then moved his thumb nail along the
rule.
“About an inch and a half in length,” he said.
“That is about right,” said his uncle. “Are these two beetles exactly
alike?”
“They are both about the same shape and colour. One is slightly bigger
than the other. They are both greenish-black above and brown below.
There is a curious broad border of yellow all round the edge of their
bodies,” said Tom.
“But they are not both exactly alike,” said Frank, “I notice that one is
smooth on the back, while the other’s back is all grooved.”
“You are right, Frank,” said Uncle George. “The one with the grooved
wing-cases is the female. The one with the smooth cases is the male.
[Illustration: Fore Leg of Male, showing Sucker Organ.]
“Notice the long legs they have for swimming, and how they seem to oar
themselves through the water. Notice also that the male has a large flat
disc upon each of his fore legs. These are suckers, by which he can
cling to things.”
“Why do they come up to the surface so often?” Frank asked.
“They cannot live without air. They carry a supply of air under their
wing-cases. They just come up to renew it from time to time. This is
done by thrusting the end of their bodies out of the water as you see.”
“One would think they ought to thrust their heads out to get air,” said
Tom.
“That seems more natural to us, because we breathe with our mouths,”
said Uncle George. “These animals take in air with their tails. A great
many pond insects breathe in this curious way.”
“What do they feed upon?” Frank asked.
“They are fierce, greedy creatures,” his uncle replied. “They attack and
kill worms, tadpoles, and even small fishes.”
Uncle George threw a small worm into the tank. One of the beetles seized
it at once and began to devour it greedily. Presently the other beetle
seized an end of the worm. The boys watched closely, and saw that the
beetles’ jaws moved from side to side like a pair of pincers.
Next morning, when Uncle George and the boys went in to see the beetles,
they found only one in the tank. The other had escaped during the night.
After a careful search they found it, at the far end of the room, dead.
“Now, how do you think this beetle managed to get out of the tank and
travel all that way?” Uncle George asked.
“It must have crawled up the inside of the tank, then down the outside.
Then it must have fallen off the window-sill, and crawled right across
the floor,” said Frank.
Uncle George shook his head.
“It might,” he said, “have managed to crawl up to the edge of the tank
so long as its legs were wet. But as its long legs are made for
swimming, and not for crawling with, I can hardly see how it could have
crawled or walked all that distance.”
“Then how did it get there, Uncle George?”
In answer to Frank’s question, his uncle took the dead beetle, and
placed it on a piece of paper on the table. He next moved aside each of
the large black wing-cases with a pin.
Underneath these wing-cases the boys saw a pair of large wings neatly
folded up. Uncle George removed one of the wing-cases, and unfolded one
of the wings. Stretched out, it was longer than the beetle’s body, and
it seemed to be made up of thin, clear skin, stretched on a framework of
long, thin supports.
“Why, these beetles can fly,” said Tom.
[Illustration: Male and Female Beetles, showing Flying Wings.]
“Of course they can,” said his uncle. “All beetles can fly. This
creature has evidently been flying about the room all night. These
insects are furnished with wings, so that they may be able to fly to
another pool when food gets scarce, or when their pool dries up.”
Exercises on Lesson VI.
1. Would you keep water beetles, tadpoles, and stickle-backs together?
Give your reasons.
2. Water beetles cannot live without air. Explain how they get it.
3. Compare the legs of a water beetle with those of any of our garden
beetles.
4. Why are water beetles furnished with wings?