We cannot help destroying some beetles when there are so many that they eat our crops. But it is pleasant to know that there are others which do us so much good that we need not wage war upon them.
The Tiger-beetles (1, Plate, p. 36), for example, are very hungry creatures; but, as they feed on other insects, they destroy the weevil and cockchafer grubs, wireworms and caterpillars, and so save our plants. Their name is given to them because they are so fierce and cunning. They are not very large—our common tiger-beetle is not more than three-quarters of an inch in length—but their long slender legs are very strong, and they can fly very fast.
There are always plenty running about in the hot sun across dry, dusty fields or commons in summer. Their wing-cases are a beautiful shining green colour shot with copper, and dotted with five yellow spots. They run very gracefully, and so fast that you will find it difficult to catch one. Just as you think you have it, it will suddenly open its wing-cases, spread its delicate transparent wings, and be off almost before you can see it go.
But if you can catch it, you will see that it has large eyes standing out on each side of its head and two sharp jagged jaws for tearing its prey, while the lower ones are covered with stiff bristles which help to hold it.
And now you must look for its grub, which is a very curious creature. The best way to find it is to go to some soft part of a sandy field where you have seen the Tiger-beetles running about. Then look at any small holes in the sand, and try to find one which leads to a tunnel in the ground. The grub of the Tiger-beetle sits at the mouth of this tunnel to catch insects as they pass. It will disappear as soon as you come near, but if you put a blade of grass into the hole and shake it, the grub will grasp the blade, and you can pull it out.
Then you can see the tools it uses. It is a long soft white grub with a horny head, and jaws like sickles, and, besides its six brown spiny feet, it has two soft humps on its back with little hooks on them. As soon as this grub is hatched in the ground, it scoops a tunnel in the soft sand with its spiny legs, and pulls itself up to the top, holding on by its legs and the hooks on its back. Its head just fills the hole, and as it is a poor weakly creature and cannot move fast, it keeps quiet till some insect passes, and then darts its head out and pulls its victim down. If you have the patience to find some of these tunnels, and sit still and watch, you may see the grub catch its prey.
The Rove or Cocktail-beetles (2, p. 36), which we found in the first lesson, are very useful in eating insects, though they are not beautiful. But the Ground-beetles, which have only small wings under their wing cases, and seldom fly, are the best hunters. You may sometimes see a good-sized beetle with long legs running along through the grass. Its body is very dark, shaded with red and violet. This is the Violet Ground-beetle, and it is hunting for grubs and wireworms.
There are some very curious beetles not difficult to find which will interest you. These are the Sexton, or Burying-beetles. When you see a dead mouse or bird lying in some part of the field or garden, pick it up quietly. If it has been there a few days it will already have a bad smell, and you are almost sure to find underneath it two or more beetles with thick bodies and strong legs. They are generally black with red feelers, and two light red bands on their abdomen. These are Sexton-beetles (3, p. 36), which have scented the dead body and flown, often for some distance, to bury it.
They scrape away the soft ground underneath, till the body sinks down, and then they drag the earth over it. Why do you think they do this? Because the mother beetle wants to lay her eggs there that the grubs may feed on the flesh. She does this as soon as the animal is buried, and in a few days the grubs are hatched. They are narrow, and each has six legs and a number of spines along its back. With these it wriggles through the flesh, and eats away till it buries itself in the ground and turns into a beetle.
A great many beetles are useful to us by eating dead and living animals. Among these are the little black shining Mimic-beetles, which draw up their legs and pretend to be dead when they are touched, and the Glow-worms, which shine so brightly in the lanes in the summer nights.
A good gardener who sees a glow-worm in a hedge will always pick it up gently, and put it in his garden when he has the chance. For the young of the glow-worm is a soft grub (3, p. 40), which works its way into the shells of small snails and feeds upon them.
If you find a dry snail-shell with a white grub in it, it will most likely be the grub of the glow-worm. You may know it by a tuft of white threads on its tail, which it uses to brush off the slime of the snail from its back.
When they are full-grown you will find the mother glow-worm (1) very easily at night, because she gives out such a bright light. She has no wings, and you might take her for a slug if you did not notice her six little legs. The male glow-worm (2) has two spots of light near his tail. But he is not so bright as the female. He has long soft wing-cases and broad wings, with which he often flies into a lighted room when the window is left open.
The last useful beetle we can mention is the little Ladybird. She feeds all her life long on the plant bugs and aphides which destroy our plants. Wherever there are plant-lice, there the ladybird lays a bunch of yellow eggs and, when they are hatched, the long dark grubs clamber up the plant stalks and poke the lice into their mouths with their front feet. After a time each one glues its tail to a leaf and hangs till it becomes a ladybird, and then it flies away to feed on plant-lice on some other bush and to lay more eggs.
Bring in a Tiger-beetle, and try to find its grub. Search for Sexton-beetles under dead animals. Bring in a Mimic-beetle. Find a male and female glow-worm. Look for the grub of the Ladybird.