An Elementary Study of Insects Part 5

Collect packets of eggs and count them. How many eggs in most packets?

How are they attached to the leaf? How large are the grubs when they hatch from the egg? Examine the grubs where they are feeding on potatoes. Do they eat holes through the leaf, or do they eat away the entire leaf? How fast do they grow? Collect a few in a gla.s.s tumbler.

Feed them and watch them grow. What do they do when you touch them? What does the hard backed beetle do when it is touched? Collect some of the large grubs with tightly stuffed bodies and put them in a jar with dirt or sand and see where they go. After a week dig them out and see what they look like.

[Ill.u.s.tration: The Colorado potato beetle showing stages of development and work on a potato plant. Note the small patch of eggs and different sized grub on the plant and the grub, pupa and adult at side.]

Write a short description of the eggs, grubs and beetle, its work and means of killing it when it is feeding on potatoes. Make careful drawings of a cl.u.s.ter of eggs, the grub and the beetle.

CHAPTER XII

THE LADY-BEETLE

"_Hurt no living thing: Ladybird, nor b.u.t.terfly, Nor moth with dusty wing, Nor cricket chirping cheerily, Nor gra.s.shopper so light of leap, Nor dancing gnat, nor beetle fat, Nor harmless worms that creep._"

--CHRISTINA ROSSETTI.

The lady-beetles comprise one family of small beetles, which is famous for the number of beneficial forms it includes. With but two exceptions the American forms feed upon other insects, in most cases pests such as plant-lice and scale insects. From the time they hatch from the egg until they pupate and again after the beetle stage is reached they are regular tigers after plant-lice. They catch and hold their prey between the front feet while they devour it bodily. The larva of the lady-beetle has an astonishing capacity for in one day it will eat several times its own weight of plant-lice. Farmers and fruit growers could hardly get along without the help of these small beetles and yet unfortunately thousands are often destroyed by those who do not know of their beneficial work.

[Ill.u.s.tration: The spotted lady-beetle; a, larva; b, pupa; c, adult; enlarged. (After Chittenden, U. S. Dept. Agri.)]

The lady-beetles, or lady-birds as they are often called, are fairly uniform in shape and color. They are oval or round in outline with the back rounded or elevated and the underside flat. In color they are usually either orange or yellow, checkered or blotched with black or black with yellow or bright orange markings. They closely resemble small tortoises. Unfortunately several plant feeding beetles are similar in shape and color which casts reflections on the lady-beetles.

[Ill.u.s.tration: The convergent lady-beetle; a, adult; b, pupa; c, larva; all enlarged. (After Chittenden, U. S. Dept. Agri.)]

The grub of the lady-beetle is usually black or dull colored with red or yellow markings which make it very conspicuous. It runs about over foliage and is broad in front and tapers to a point behind. When the grub is full fed it attaches the top of its body to a leaf, twig or other object and pupates. In the pupal stage it is often protected with spines and is able to lift the front end of the body up and down when disturbed, producing a light tapping sound.

The lady-beetle usually hides in rubbish about the base of trees or in some cases even enter homes for the winter months, coming out with the spring to deposit small ma.s.ses of oval yellow or orange eggs on plants infested with lice. They breed rapidly and with the help of parasites and other beneficial insects usually control the plant-lice pests.

OBSERVATIONS AND STUDIES

Examine about fruit trees, shade trees, truck crops and in wheat fields for the brightly marked beetles. Watch them move about the plant in search of food. Can they fly? Do you find them eating the leaves? Do you find any green lice near them? See if they feed on these lice. Examine also for the soft bodied, tiger-like grubs. Do they eat the lice? Do they travel fast? Have they wings? See if you can find any of the pupae attached to limbs or twigs and if so, tickle them with a straw or a pencil and see them "bow." Keep a record of the different trees and plants on which you find lady-beetles.

Collect several of the beetles and the grubs and keep them in a bottle or jelly gla.s.s. Leave them without food for a day and then give them some green plant-lice and watch them devour the lice. How many lice can one eat in a day? How do they go about devouring a louse? Do they simply suck out the blood, or is the louse completely devoured? Supposing that for each apple tree in Missouri there are one hundred lady-beetles and that each beetle devours fifteen lice in a day, does it not seem worth while protecting them and encouraging such work? A little time spent in acquainting one's self with the good work of such forms as these will help greatly in the fight on our insect foes. Make drawings of and describe briefly the different stages of the lady-beetles.

CHAPTER XIII

THE DRAGON-FLY

What child is there that is not familiar with the insect commonly known as the dragon-fly, snake doctor or snake feeder? Every lover of the stream or pond has seen these miniature aeroplanes darting now here, now there but ever retracing their airy flight along the water's edge or dipping in a sudden nose dive to skim its very surface. At times it is seen to rest lazily, wings out-stretched, perched on some projecting reed or other object. But when approached how suddenly it "takes off"

and is out of reach. The dragon-fly is an almost perfect model of the modern monoplane. Its two long wings on either side are the planes, its head the nose, its thorax the fuselage and its long projecting abdomen the tail or rudder. On wing the dragon-fly is one of the swiftest and most powerful insects. The dragon-flies are found all over the world being most abundant in the warmer regions where rainfall and bodies of water are abundant. For breeding they require water, their immature stages living under water feeding on aquatic animal life. Our present order of dragon-flies is the remains of an ancient race of insects of immense size. From fossil remains we learn that ancient dragon-flies had a wing expanse of three feet.

[Ill.u.s.tration: Cast off skin of dragon-fly nymph, showing shape and position taken on a twig when the adult winged form emerged from the last nymph stage.]

The dragon-fly is a beneficial insect thruout life. The young feed on mosquito wigglers and similar life in ponds and streams while the adults dart here and there over ponds, fields or lawn catching mosquitoes and other winged insects. Many look upon the dragon-fly as a dangerous stinging insect but it is entirely harmless and can be handled without the least danger. They vary greatly in size and appearance. The so-called damsel-flies form a group of dragon-flies or Odonata which rest with the wings in a vertical position and the young aquatic stages are more slender. In color markings dragon-flies include all hues of the rainbow tho as a rule they do not have such extravagant colors as the b.u.t.terflies.

[Ill.u.s.tration: One of our common dragon-flies found about ponds and streams.]

OBSERVATIONS AND FIELD STUDIES

Go into the fields and study and collect the different kinds of dragon-flies and their young stages from the bottoms of ponds. How swiftly can they fly? Do they fly high in the air as well as near the water or surface of the earth? Can you see them catch other insects? Do birds catch them and eat them? Take a position along the edge of a pond and as they come flying by swing swiftly with your net and catch one.

Examine it carefully. Note the strength of the long, slender wings with their lace-like network of veins. Measure the distance across the back from tip to tip of wings. Compare this with the length from tip of head to the tip of the abdomen. Examine the head with its large compound eyes and the chewing mouth parts. Note the strong thorax which is filled with muscles to operate the wings in flight. How many segments are there to the abdomen?

With the hands or with a bucket dip up a quant.i.ty of mud and trash from the bottom of a pond and pile it on the bank. As the water soaks away watch for signs of life in the ma.s.s. If you find a few small creatures, say half an inch long with large head and eyes, broad body and with six rather long legs they are probably the nymph stages of dragon-flies.

Wash the mud off of them so that you can examine them carefully. With a straw probe in the mouth and you will find that the lower lip is a long elbowed structure which can be suddenly thrown out in front of it and with a pair of pincher-like p.r.o.ngs at the tip it can catch and hold its prey. Some forms keep their bodies covered with mud so that they can slowly creep up close to their prey.

Collect several nymphs and keep them in a jar of water and study their movements and feeding habits. Disturb one with a pencil or straw and see how it darts forward. It has a water chamber in the large intestines, including also the respiratory tracheal gills, from which the water can be suddenly squirted which throws the insect forward. The escaping stream of water forces the insect forward on the same principle as the rotating lawn sprinkler. If you collect some almost mature nymphs and keep them for a time in a vessel of water you may see them crawl out of the water, shed their skin and change to winged adults. Collect a few adults of different species for pinning in your permanent collection.

CHAPTER XIV

THE SQUASH BUG

This common blackish or earth-colored bug is usually called the squash stink-bug. It has a very disagreeable odor which gives it this name.

When disturbed it throws off from scent glands a small quant.i.ty of an oily substance which produces this odor. This is a protection to it for few birds or animals care to feed on it. Most species of sap or blood sucking true bugs have a similar protecting odor.

The squash bug feeds largely on squash and pumpkins. It has a slender beak with needle-like mouth parts which are stuck into the plant for extracting the sap. It feeds only on plant sap. When it can not get squash or pumpkins it will feed on watermelons, muskmelons and related crops. It is very destructive to these crops. It not only extracts sap thus weakening the plant but it also seems to poison the plant while feeding. In this way its bite injures the plant something like the effects of the bed-bug's bite on our flesh. It feeds first on the leaves and vines often killing them in a few days. Later it may cl.u.s.ter and feed on the unripe squashes or pumpkins in such numbers as to completely cover them. Every country boy or girl has seen these stinking bugs on pumpkins in the corn field, at corn cutting time in the fall.

[Ill.u.s.tration: Pumpkin in field covered with adults and nymphs of squash stink-bug.]

The squash bug lives thru the winter as the matured winged insect. It flies from its food plant to winter quarters late in the fall. For winter protection it may enter buildings, hide under shingles on roofs, crawl into piles of lumber, under bark of dead trees or stumps or hide under any similar protection. When its chosen food crops begin to come up in the spring it leaves its winter home and flies in search of food.

After feeding for a time the female lays patches of oval, flattened, gold-colored eggs set on edge. When first deposited the eggs have a pale color but in a short time the golden color appears. In some cases only three or four eggs may be found in one patch while again there may be twenty or thirty of them. They are so brightly colored that they can easily be seen and most boys and girls have seen them on the leaves of squashes or pumpkins.

[Ill.u.s.tration: Cl.u.s.ter of golden-brown eggs of squash stink-bug showing two recently hatched nymphs.]

In a few days after they are laid they hatch and out of each crawls a small, long-legged blackish or greenish young bug called the nymph.

These little fellows usually stay in a crowd hiding on the under side of a leaf. After feeding for a time their leaf begins to turn yellow and soon dies. Then they move to a new leaf. As they feed they grow rapidly and after shedding their skins they change to the second nymph stage.

This shedding of their skins or molting occurs five times before they mature. Of course each time before the old skin or suit of clothes is discarded a new one is developed beneath. The females may continue to deposit eggs for later cl.u.s.ters of young. They become most abundant on the crop late in the fall. Just before cold weather sets in the adults again seek winter shelter.

This is a very difficult insect to control. Since it feeds on liquid sap only it is impossible to kill it by spraying the crop with a poison such as a.r.s.enate of lead. It can not chew and swallow such poison. The young can be killed fairly well with a spray or dust containing nicotine but such treatments are not effective against the adults or nearly mature nymphs. A better method is to destroy all the bugs possible in the fall before they go to the winter protection and then watch for and destroy the adults and the eggs ma.s.ses in the spring when they appear on the young crop. If the first adults and the eggs and newly hatched nymphs are destroyed the crop can be protected against the destructive work later.

OBSERVATIONS AND FIELD STUDIES

Plant a few squash hills in the garden in the spring and also plant a few seeds in rich dirt in discarded tin cans or flower pots. As the spring advances and the squashes start to vine watch for squash bugs on them. Examine in piles of lumber, stove wood and under bark for some of the bugs before they come to the squash hills. If any are found put them on the squash plants in flower pots and cover them with a pint mason fruit jar. Watch for eggs to appear on the plants and also examine for eggs on the squashes in the garden. When eggs appear examine them carefully, measure them and write a brief description of them. Try to mash them between your fingers. When they hatch carefully study the young nymph and describe it. Can you see the slender beak which incloses the mouth parts? How many joints are there to the antennae? As the nymph grows watch it shed its skin. How does it do it? Where does its skin first crack? Save the cast skin and try to follow the nymph thru all the nymph stages to the adult. Collect a bottle of the nymphs of varying sizes from the garden. Examine them and describe the different stages.

Can you see the wings forming on the backs of the older nymphs? How many small wing pads are there? Examine the adult closely and write a careful description of it. Can you find where the secretion that causes the odor is produced? How long will the odor stay on your hands? Can you wash it off? Spread the wings of the adult and make a careful drawing of one front and one hind wing showing accurately the wing veins. In the garden try to protect all the hills of squash from the bugs except one or two used for your studies. Write a brief description of your methods of control.

[Ill.u.s.tration: Squash stink-bug adult and nymph extracting sap from squash.]