An Elementary Study of Insects Part 3

CHAPTER VI

THE CABBAGE MILLER

"_And here and yonder a flaky b.u.t.terfly Was doubting in the air._"

--MCDONALD.

With the first approach of spring comes swarms of large green flies which bask in the March sun on the south sides of buildings. They are not with us long, however, until we notice flashes of white quickly moving about from one early weed to another. These are the advance guards of the cabbage millers or b.u.t.terflies. All through the cold winter they remained in the chrysalis stage stuck to the sides of houses, fence posts and in other protected places, awaiting the first breath of spring. The first adults to emerge find no cabbage on which to lay their eggs so they are compelled to use other plants such as pepper gra.s.s.

[Ill.u.s.tration: Egg of cabbage miller much enlarged.]

The eggs are very small and are usually placed on the lower edge of the leaf. These hatch and the small green worms appear. Throughout the summer there are a number of broods produced and an enormous amount of damage is done. Just before frost the last caterpillars search for protected places where they pa.s.s to the pupal or resting stage for the winter. No coc.o.o.n is spun by this caterpillar.

Where measures are not taken to control the cabbage worms they destroy much of the cabbage crop each season. The white b.u.t.terflies can be seen any day during the summer visiting cabbage, mustard, radishes and other similar plants. By destroying all of the worms and millers in the early spring one has less trouble later. This can be done by hand picking, or where the patch is large by spraying with a poison solution to which soap is added to keep the solution from rolling off in large drops.

Poison can be used until the heads are well formed, but if the first worms in the spring are destroyed, later spraying is unnecessary though an occasional handpicking will help.

OBSERVATIONS AND STUDY

[Ill.u.s.tration: Cabbage worm feeding, slightly enlarged.]

Go into the garden and examine the cabbage for small green worms which vary from one fourth to a little over an inch in length. What is the nature of their work on the leaf? Where do they feed most, on the outer or inner leaves? Do they eat the entire leaf? How does the work of the young worms differ from that of the larger ones? Do they spin silk? Are they on the top or under side of the leaf? Examine under the dead and dried leaves at the ground and see if you can find small, hard, gray objects which have sharp angles and which are tied to the leaf with a cord of silk. What are these objects? Watch the miller as she visits the cabbage and see if you can find the small eggs which she lays on the under side of the leaves. When she visits a cabbage plant she bends her body up under the outer leaves and stops but a moment, fluttering all the while as she sticks the small egg to the leaf. It is about the size of a small crumb of bread. What does the miller feed on? Does she visit flowers? If so, what flowers?

[Ill.u.s.tration: Pupa or chrysalis of cabbage miller.]

BREEDING WORK

Collect a few of the worms and put them in a gla.s.s jar with a piece of cabbage leaf. Examine them carefully and watch them crawl. How many legs do they have? Where are they placed on the body? How can they use so many legs while crawling? How many joints are there to the body? Note the short fine hair all over the body which gives it the appearance of green velvet. What color is the head? How does the caterpillar feed?

Write a brief description of the worm. Do not mistake it for the cabbage span-worm which is also green, but which walks by humping up its back.

[Ill.u.s.tration: Cabbage miller on red clover blossom.]

Keep the cabbage worms in the jar for a few days and watch them disappear. After they have disappeared, what is left in the jar? These are the chrysalids or pupae of the insect and later from them will come the millers. Take one of the pupae in your hand and see if it can move.

If it is in the summer the miller will appear in a week, but if it is in the late fall it will simply pa.s.s the winter in the pupa stage. Watch the miller escape from the pupal case and describe it. Examine the miller carefully and describe briefly the number of legs, wings, segments of body, sucking tube and color markings. Make careful drawings of the caterpillar, chrysalis and b.u.t.terfly. What gives the color to the wings? Rub the wings between your fingers and see if the color comes off. The wings are covered with very small scales of different colors which combine to give the beautiful markings. The wings of all b.u.t.terflies and moths are covered with scales and hairs in this way. In this insect we find both chewing and sucking mouth parts. The caterpillar chews while the parent b.u.t.terfly has a long tube for sucking up nectar from flowers and water from puddles in the road.

"_Far out at sea--the sun was high, While veered the wind and flapped the sail; We saw a snow-white b.u.t.terfly Dancing before the fitful gale Far out at sea._

"_The little wanderer, who had lost His way, of danger nothing knew; Settled a while upon the mast; Then fluttered o'er the waters blue Far out at sea._

"_Above, there gleamed the boundless sky; Beneath, the boundless ocean sheen; Between them danced the b.u.t.terfly, The spirit-life of this vast scene, Far out at sea._

"_The tiny soul that soared away, Seeking the clouds on fragile wings, Lured by the brighter, purer ray Which hope's ecstatic morning brings-- Far out at sea._

"_Away he sped, with shimmering glee, Scarce seen, now lost, yet onward borne!

Night comes with wind and rain, and he No more will dance before the morn, Far out at sea._

"_He dies, unlike his mates, I ween Perhaps not sooner or worse crossed; And he hath felt and known and seen A larger life and hope, though lost Far out at sea._"

--R. H. HORNE.

CHAPTER VII

THE APPLE WORM

[Ill.u.s.tration: Apple worms in core of apple. Usually only one worm appears in an apple. Note the decaying of the apple.]

This is perhaps the most destructive insect pest attacking the apple.

Every year, that we have a good apple crop, there are thousands of bushels of wormy apples which are practically worthless. This means an actual loss of thousands of dollars a year to the apple growers of this country. For this reason alone each child should come to know the life history, habits and injury of this pest. It is most destructive to the apple though the pear comes in for its share.

[Ill.u.s.tration: The codling moth slightly enlarged. (From Slingerland).]

Every country child and many of those of the cities, are familiar with this worm for they often bite into it while eating apples. The small worms crawl down in the blossom end of the young developing apple and from there bore into the pulp and eventually reach the core of the fruit. They stay in the apple about six weeks when they eat a hole out to the surface and crawl down to the trunk where loose bark offers a hiding place. Here they spin their coc.o.o.ns and change to a small, brown, plump pupa and after a few days the winged moth emerges. The moth is very small and is not often found by one not acquainted with it. They come out during late June and early July when they lay eggs for a second colony of worms which again enter the fruit and destroy more of it.

These worms of the second brood are usually mature and leave the fruit about the time apples are picked in the fall in central Missouri. They escape and soon spin coc.o.o.ns in which they pa.s.s the winter. Early in the spring these change to pupae and later the moths come out. They appear about the time apples bloom in the spring and lay the eggs for the first worms which enter in great numbers at the blossom end.

This in short, is the life story of the pest through the year. Little can be done to destroy the pest after it gets into the fruit, therefore remedies must be applied to destroy the worm before it gets into the fruit. All orchards should be sprayed with a poison in the spring before the worms appear. Since most of them enter by way of the blossom end, it is necessary that the poison be put into the blossom end. To do this spray at once after the blossoms fall, repeat after two weeks and spray again in July to kill the second brood of worms. The protection of woodp.e.c.k.e.rs and sapsuckers will also help as they feed on the worms under the bark.

[Ill.u.s.tration: Apple blossoms at about the right stage for receiving the first and most important a.r.s.enical spray for the control of the apple worm.]

OBSERVATIONS AND BREEDING WORK

Go into the orchard and examine for apples with ma.s.ses of sawdust-like material projecting from the sides or blossom end. By removing this brown deposit which is the excrement of the worm, you will find a hole leading into the apple. Cut open one of these and determine the course of the tunnel. Where do you find the worm? Do all such apples contain worms? Where have they gone? How does the feeding of the worms injure the fruit? Do any of the wormy apples show rot? Are any of the windfalls in the orchard wormy and if so what proportion?

Remove a worm from one of the apples and examine it. How many legs has it? What color is it and does it have hair upon its body? Can it crawl fast? Does it spin silk? Put a number of the large worms in a jar and examine from day to day and keep records of what happens. Collect a number in the fall and keep them in a box outdoors during the winter. In the spring watch them change to the pupa in the coc.o.o.n and a little later the mature insect or codling moth, as it is commonly called, will emerge. Describe the moth and pin a number of them for your collection.

What time in the spring do the caterpillars change to the pupa and when do the moths emerge? If you keep the moths in a bottle they will lay their small circular flat eggs where they can be seen by looking closely. During the winter examine under the bark of apple trees and in cracks and crevices about apple pens for the small silk coc.o.o.ns containing the worms. Examine in the same places in the spring about apple blooming time and then in place of the small pink worms you will find the small brown pupae. Keep these a few days and the moths will appear.

What proportion of apples in your region are wormy? What are they used for? Are the trees sprayed just after the blossoms fall to control the pest? Where spraying is carefully done, are there as many wormy apples?

Why not spray all the orchards properly and have no worms?

Draw and describe the different stages of the apple worm or codling moth and its injury to fruit.

"_O, yet we trust that somehow good Will be the final goal of ill, To pangs of nature, sins of will, Defects of doubt and taints of blood;_

"_That nothing walks with aimless feet; That not one life shall be destroyed, Or cast as rubbish to the void, When G.o.d hath made the pile complete;_

"_That not a worm is cloven in vain, That not a moth with vain desire, Is shrivelled in a fruitless fire, Or but subserves another's gain._"