An Elementary Study of Insects Part 4

--TENNYSON.

CHAPTER VIII

THE TOMATO OR TOBACCO WORM

[Ill.u.s.tration: Egg of Tomato worm moth enlarged.]

This insect is often very destructive to tomatoes and tobacco. Most country boys and girls know it and fear its ugly looking horn. When full grown it is four inches long, usually dark green with a number of slanting white lines along either side. It is so near the color of the plants that it is difficult to see it.

[Ill.u.s.tration: Young tomato worm.]

During the summer months the worms are common, being most abundant in August. In the fall the mature worms go into the ground and change from the worm to a large, oval, brown pupa with a jug-handle-like appendage on the under side. These are often turned up when the garden is plowed in the spring. After tomato plants are well started the large greyish humming-bird-like moths comes from the ground and begin laying eggs. The moth expands from four to six inches and is often seen at dusk visiting the blossoms of "jimson weed" and other large tube flowers. They are also found around lights at night.

Where they are troublesome the plants should either be sprayed with a poison when the injury is first noticed or else the worms should be picked off and destroyed. There is a small parasitic wasp which is very helpful in destroying this caterpillar. They live inside the worm and when mature bore out through the skin on the sides and back where they spin small white egg-like coc.o.o.ns from which later the small wasps emerge. Often a hundred or more may come out of one worm.

STUDY AND OBSERVATION

Observe the worms where they are at work on tomatoes. Disturb them and hear them grind their jaws together. Do they eat the foliage rapidly?

Dust a little Paris green on the foliage where a worm is eating and see what happens in half an hour. Collect a number of the worms in a gla.s.s fruit can and give them tomato leaves to eat and watch them grow. How many segments are there to the body? How many of the segments have small black spots on either side? These are holes through which the worm breathes. Is the horn at the end of the body stiff enough to stick into your hand? This is thought to be a sting but it is only an ornament and is entirely harmless. When full grown they will burrow into the sand in the jar and change to the pupa.

[Ill.u.s.tration: Full-fed tomato worm slightly reduced.]

[Ill.u.s.tration: Chrysalis or pupa of tomato worm. Note the jug-handle-like sheaths enclosing the proboscis.]

Examine the brown pupa carefully and see if it can move. What is the peculiar structure on the under side of the body? The moth which comes from this in the spring is very large. It is covered with white and black scales and hairs which give it a mottled appearance. Examine on the under side of the head for a peculiar structure like a watch spring.

This is the sucking tube used in drawing up nectar from deep tubular blossoms. When the moths are sipping nectar from "jimson weed" blossoms they can be killed by pouring a little poison down into the blossoms.

[Ill.u.s.tration: Tomato worm moth natural size.]

CHAPTER IX

THE FIREFLY

This insect is of little economic importance to us at present but its peculiar habit of producing light makes it a very striking form and one which deserves study. The firefly is a beetle, and begins to make its appearance the latter part of June when the darkest nights may be one solid glow of fire. They live largely in damp places and bottoms at night are specked with their tiny flashes of light. The larval or grub stage is pa.s.sed on the ground beneath gra.s.s, weeds and rubbish where they often prey upon other insects. In some cases the grubs may be able to produce light though as a rule the luminous grub-like creature or glow-worm is a wingless adult firefly.

OBSERVATIONS AND STUDIES

Watch for the first appearance of the fireflies in the evening and see where they come from. Do they all appear at once or only a few at first?

Do they fly fast? How often is the light produced? Will they produce the light while on the ground? When they fly do they stay near the ground or high in the air? Do they light in trees?

[Ill.u.s.tration: Firefly beetles on sour-dock leaf.]

Catch one of the fireflies in your hat and examine it carefully. How large is it? Describe briefly its size, shape and color. Are its wing covers hard like other beetles? Where is the light produced? What color is the light? Is it bright? Hold the firefly on the opposite side of a sheet of paper and see if the light will show through. Try the same with your hat, coat sleeve and other objects. This light is extremely penetrating and unlike the light of a lamp is produced with the generation of very little heat. Will it continue to flash while you hold it? Are the segments from which the light comes the same color as the other segments of the body? Crush the tip of the body between your thumb and finger and see if the light continues to appear. How long does it last? Collect a number of the fireflies and put them in a bottle and see if the light is strong enough to enable you to read.

The firefly has proven to us that our methods of producing light are extremely wasteful since much of the energy is lost in heat and it is possible that through the lesson of the firefly we may some day be able to produce better light at less expense.

[Ill.u.s.tration: Lower surface of firefly beetle enlarged to show the light producing segments of the abdomen.]

CHAPTER X

THE WHITE GRUB OR JUNE-BUG

[Ill.u.s.tration: White grub feeding on roots of corn plant, enlarged.]

This insect is more familiar to country children in the grub stage.

Every one who has followed a plow in rich sod land has seen these fat, white coiled grubs roll down into the furrow when the plow turns them up. They are in the ground feeding on the roots of plants. Often all the roots of gra.s.s in lawns and meadows are eaten off and the sod dies and can be rolled up like strips of carpet. This insect breeds largely in sod and when this is plowed under and other crops are planted the grubs may injure them severely. Corn, wheat, oats and truck crops are severely injured. In some cases the grubs may feed for three years before they change to the pupa and later to the adult beetle. To control this pest, plow in the fall and rotate crops, so that sod will not remain on the same land too long.

[Ill.u.s.tration: June beetle showing stages of development. The larva or grub worm is feeding on roots under ground; the pupa and adult are shown above ground.]

The beetles come from the ground or may be plowed out in May and June and are commonly spoken of as May-beetles or June-bugs. They are usually of a yellowish-brown color and are often troublesome coming into the house at night where they buzz about the light, b.u.mping into everything until they finally drop heavily to the floor. All country boys and girls know these beetles.

OBSERVATIONS AND STUDIES

Collect a number of the grubs from the ground and examine them for legs, eyes and mouth. How many legs have they? Can you find eyes? What use would they have for eyes while in the ground? Do they bite? Place them on the table and see how they move. What color are they? Do you find spines or hair on their bodies? Pull up a little gra.s.s by the roots and put it in a jelly tumbler with soil and put some of the grubs in with it. Water it so as to keep it growing and follow the development of the grubs.

Collect some of the beetles and put them in a bottle and watch them crawl about. Where are their wings? How can they get them out when they want to fly? How many legs have they? Examine the tip of the feet for hooks. What are these used for? Can they chew leaves? Where are their eyes? Do you find feelers and if so where?

Write a short description of the grub and the beetle and make careful drawings of them.

CHAPTER XI

THE COLORADO POTATO BEETLE

This is one of the worst pests of the potato. As the name would imply it came originally from Colorado but is common now all over the country.

The full grown insect is short and thick with a hard sh.e.l.l, striped with yellow and black. The grubs, on the other hand, are soft and red or orange with black spots. Both the grubs and the beetles feed on potatoes and often completely strip them of their leaves. Since they feed on foliage they can be very quickly destroyed by dusting or spraying the plants with a poison such as Paris green or a.r.s.enate of lead. The patches of yellow or reddish eggs are found mostly on the under side of the potato leaves. When the fat grubs are full-fed they go into the ground and change to pupae and later to the striped beetles. This pest should not be mistaken for the so-called old-fas.h.i.+oned potato beetles which are long and slender and either bluish grey in color or striped with yellow and black. These are blister beetles and are entirely different.

OBSERVATIONS AND STUDIES

Watch for the first appearance of the adult beetles in the spring when the potatoes are just beginning to come up. They pa.s.s the winter under ground and in the spring come out ready to lay eggs on the young potatoes. Collect and examine the adults. How many stripes have they?