Chapter XXIII: Part II: Animal Life (16)

The caterpillars, as they hatch from the eggs, have bodies ringed with black and yellow. They are sociable little fellows and live together side by side amicably, not exactly “toeing the mark” like a spelling class, but all heads in a row at the edge of the leaf where each is eating as fast as possible. When they are small, the caterpillars remain on the under side of the leaves out of sight. In about five days, the first skin is shed and the color of the caterpillar remains about the same. Four or five days later, the second molt occurs, and then the caterpillar appears in a beautiful bluish green costume, with black tubercles, except four large ones on the second and third segments, and one large one on the eleventh segment, which are yellow. This caterpillar has an interesting habit of weaving a carpet of silk on which to change its skin; it seems to be better able to hold on while pushing off the old skin, if it has the silken rug to cling to. After the third molt, the color is a deeper greenish blue and the black tubercles are smaller, and the five big ones are larger and bright orange in color. After the fourth molt, which occurs after a period of about five or six days, the caterpillar appears in its last stage. It is now over two inches long, quite smooth and most prosperous looking. Its color is a beautiful, light, greenish blue, and its head is yellow. It has six rows of short, round, black tubercles. The four large tubercles at the front end of the body are red, and the large tubercle on the rear end of the body is yellow.

The cynthia is a beautiful moth which has come to us from Asia; it is very large with a ground color of olive-green, with lavender tints and white markings; there are white tufts of hairs on the abdomen. It builds its cocoon like the promethea, fastening the petiole to the twig, therefore the lesson indicated for the promethea will serve as well for the cynthia. The cynthia caterpillars live upon the ailanthus tree and are found only in the regions where this tree has been introduced.

Photo by M. V. Slingerland.]

_References_--Moths and Butterflies, Dickerson; Caterpillars and Their Moths, Elliot and Soule; Moths and Butterflies, Ballard.

Photo by M. V. Slingerland.]

LESSON LXXIV

THE PROMETHEA

_Leading thought_--The promethea caterpillar fastens a leaf to a twig with silk and then makes its cocoon within this leaf. The male and female moths are very different in appearance.

_Method_--This work should begin in the late fall, when the children bring in these cocoons which they find dangling on the lilac bushes or wild cherry trees. Much attention should be paid to the way the leaf is fastened to the twig so it will not fall. The cocoons should be kept out of doors, so that the moths will issue late in the spring when they can have natural conditions for laying their eggs, and the young caterpillars are supplied with plenty of food consisting of new and tender leaves.

_The Cocoon_

_Observations_--1. On what tree did you find it? Does it look like a cocoon? Does it not look like a dried leaf still clinging to the tree? Do you think that this disguise keeps the birds from attacking it? Do you know which birds are clever enough to see through this disguise?

2. How is the leaf fastened to the twig? Could you pull it off readily? What fastened the leaf to the twig?

3. Tear off the leaf and study the cocoon. Is there an opening to it? At which end? What is this for?

4. Cut open a cocoon. Is it as thick as that of the cecropia?

5. Study the pupa. Is it as large as that of the cecropia?

6. Can you see where the antennæ of the moth are? Can you see the wing covers? Can the pupa move?

_The Moth_

1. Are there two kinds of moths that come from the promethea cocoons? Does one of them look something like the cecropia? This is the mother promethea.

2. Are any of the moths almost black in color with wings bordered with gray and with graceful prolonged tips to the front wings? This is the father moth.

3. Make water color drawings of promethea moths, male and female.

4. If a promethea mother lays eggs, describe them.

_The Caterpillar_

1. How do the promethea caterpillars look when they first hatch from the eggs? Do they stay together when they are very young? How do they act? Where do they hide?

2. How do they change color as they grow older? Do they remain together or scatter? Do they continue to hide on the lower sides of leaves?

3. What preparation does a promethea caterpillar make before changing its skin? Why does it shed its skin? Does its colors change with every change of skin?

4. Describe the caterpillar when it is full-grown. What is its ground color? What are the colors of its ornamental tubercles? The color of its head?

5. Describe how a promethea caterpillar makes its cocoon.

THE HUMMINGBIRD, OR SPHINX, MOTHS

_Teacher’s Story_

If during the early evening, when all the swift humming birds are abed, we hear the whirr of rapidly moving wings and detect the blur of them in the twilight, as if the creature carried by them hung entranced before some deep-throated flower, and then whizzed away like a bullet, we know that it was a hummingbird, or sphinx, moth. And when we see a caterpillar with a horn on the wrong end of the body, a caterpillar which, when disturbed, rears threateningly, then we may know it is the sphinx larva. And when we find a strange, brown segmented shell, with a long jug handle at one side, buried in the earth as we spade up the garden in the spring, then we know we have the sphinx pupa.

The sphinx was a vaudeville person of ancient mythology who went about boring people by asking them riddles; and, if they could not give the right answers, very promptly ate them up. Although Linnaeus gave the name of sphinx to these moths, because he fancied he saw a resemblance in the resting or threatening attitude of the larvæ to the Egyptian Sphinx, there are still other resemblances. These insects present three riddles: The first one is, “Am I a humming-bird?” the second, “Why do I wear a horn or an eye-spot on the rear end of my body where horns and eyes are surely useless?” and the third, “Why do I look like a jug with a handle and no spout?”

From Manual for the Study of Insects.]

The sphinx moths are beautiful and elegant creatures. They have a distinctly tailor-made appearance, their colors are so genteel and “the cut” so perfect. They have long, rather narrow, strong wings which enable them to fly with extraordinary rapidity. The hind wings are shorter, but act as one with the front wings. The body is stout and spindle-shaped. The antennæ are thickened in the middle or toward the tip, and in many species have the tip recurved into a hook. Their colors show most harmonious combinations and most exquisite contrasts; the pattern, although often complex, shows perfect refinement. Olive, tan, brown and ochre, black and yellow, and the whole gamut of greys, with eye-spots or bands athwart the hind wings of rose color or crimson, are some of the sphinx color schemes.

Photo by M. V. Slingerland.]

Most of the sphinx moths have remarkable long tongues, being sometimes twice the length of the body. When not in use, the tongue is curled like a watch spring in front and beneath the head; but of what possible use is such a long tongue! That is a story for certain flowers to tell, the flowers which have the nectar wells far down at the base of tubular corollas, like the petunia, the morning glory or the nasturtium; such flowers were evidently developed to match the long-tongued insects. Some of these flowers, like the jimson weed and nicotina, open late in the day so as to be ready for these evening visitors. In some cases, especially in the orchids, there is a special partnership established between one species of flower and one species of sphinx moths. The tobacco sphinx is an instance of such partnership; this moth visits tobacco flowers and helps develop the seeds by carrying pollen from flower to flower; and in turn it lays its eggs upon the leaves of this plant, on which its great caterpillar feeds and waxes fat, and in high dudgeon often disputes the smoker’s sole right to the “weed.” Tobacco probably receives enough benefit from the ministrations of the moth to compensate for the injury it suffers from the caterpillars; but the owner of the tobacco field, not being a plant, does not look at it in this equitable manner.

Photo by M. V. Slingerland.]

The sphinx caterpillars are leaf eaters and each species feeds upon a limited number of plants which are usually related; for instance, one feeds upon both the potato and tomato; another upon the Virginia creeper and grapes. In color these caterpillars so resemble the leaves that they are discovered with difficulty. Those on the Virginia creeper, which shades porches, may be located by the black pellets of waste material which fall from them to the ground; but even after this unmistakable hint I have searched a long time to find the caterpillar in the leaves above; its color serves to hide the insect from birds which feed upon it eagerly. In some species, the caterpillars are ornamented with oblique stripes along the sides, and in others the stripes are lengthwise. There is often a great variation in color between the caterpillars of the same species; the tomato worm is sometimes green and sometimes black.

Note that the part encasing the long tongue is free and looks like the handle of a jug.

Photo by M. V. Slingerland.]

The horn on the rear end is often in the young larva of different color than the body; in some species it stands straight up and in some it is curled toward the back. It is an absolutely harmless projection and does not sting nor is it poisonous. However, it looks awe-inspiring and perhaps protects its owner in that way. The _Pandora_ sphinx has its horn curled over its back in the young stage but when fully grown the horn is shed; in its place is an eye-spot which, if seen between the leaves, is enough to frighten away any cautious bird fearing the evil eye of serpents. The sphinx caterpillars have a habit, when disturbed or when resting, of rearing up the front part of the body, telescoping the head back into the thoracic segments, which in most species are enlarged, and assuming a most threatening and ferocious aspect. If attacked they will swing sidewise, this way and then that, making a fierce crackling sound meanwhile, well calculated to fill the trespasser with terror. When resting they often remain in this lifted attitude for hours, absolutely rigid.

The six true legs are short with sharp, little claws. There are four pairs of fleshy prolegs, each foot being armed with hooks for holding on to leaf or twig; and the large, fleshy prop-leg on the rear segment is able to clasp a twig like a vise. All these fleshy legs are used for holding on, while the true legs are used for holding the edges of the leaf where the sidewise working jaws can cut it freely. These caterpillars do clean work, leaving only the harder and more woody ribs of the leaves. The myron caterpillar seems to go out of its way to cut off the stems of both the grape and Virginia creeper.

There are nine pairs of spiracles, a pair on each segment of the abdomen and on the first thoracic segment. The edges of these air openings are often strikingly colored. Through the spiracles the air is admitted into all the breathing tubes of the body around which the blood flows and is purified; no insect breathes through its mouth. These caterpillars, like all others, grow by shedding the skeleton skin, which splits down the back.

Photo by M. V. Slingerland.]

Often one of these caterpillars is seen covered with white objects which the ignorant, who do not know that caterpillars never lay eggs, have called, eggs. But the sphinx moths at any stage would have horror of such eggs as these! They are not eggs but are little silken cocoons spun by the larvæ of a hymenopterous parasite. It is a tiny, four-winged “fly” which lays its eggs within the caterpillar. The little grubs which hatch from these eggs feed upon the fleshy portions of the caterpillar until they get their growth, at which time the poor caterpillar is almost exhausted; and then they have the impudence to come out and spin their silken cocoons and fasten them to the back of their victim. Later, they cut a little lid to their silken cells which they lift up as they come out into the world to search for more caterpillars.

As soon as the sphinx larva has obtained its growth, it descends and burrows into the earth. It does not spin any cocoon but packs the soil into a smooth-walled cell in which it changes to a pupa. In the spring the pupa works its way to the surface of the ground and the moth issues. In the case of the tomato and tobacco sphinx pupa, the enormously long tongue has its case separate from the body of the pupa, which makes the “jug handle.” The wing cases and the antennæ cases can be distinctly seen. In the case of the other species the pupæ have the tongue case fast to the body. The larva of the myron sphinx does not enter the ground, but draws a few leaves about it on the surface of the ground, fastens them with silk and there changes to a pupa.

_References_--Caterpillars and their Moths, Elliot and Soule; Moths and Butterflies, Dickerson; Moths and Butterflies, Ballard; Manual for the Study of Insects, Comstock.

Photo by M. V. Slingerland.]

LESSON LXXV

THE HUMMING-BIRD, OR SPHINX, MOTHS

_Leading thought_--The sphinx caterpillars have a slender horn or eye-spot on the last segment of the body. When disturbed or when resting they rear the front part of the body in a threatening attitude. They spin no cocoons but change to pupæ in the ground. The adults are called humming-bird moths, because of their swift and purring flight. Many flowers depend upon the sphinx moths for carrying their pollen.

_Method_--The sphinx caterpillar found on the potato or tobacco, or one of the species feeding upon the Virginia creeper is in September available in almost any locality for this lesson. The caterpillars should be placed in a breeding cage in the schoolroom. Fresh food should be given them every day and moist earth be placed in the bottom of the cages. It is useless for the amateur to try to rear the adults from the pupæ in breeding cages. The moths may be caught in nets during the evening when they are hovering over the petunia beds. These may be placed on leaves in a tumbler or jar for observation.

_The Caterpillar_

_Observations_--1. On what plant is it feeding? What is its general color? Is it striped? What colors in the stripes? Are they oblique or lengthwise stripes? Are all the caterpillars the same color?

Photo by M. V. Slingerland.]

2. Can you find the caterpillar easily when feeding? Why is it not conspicuous when on the plant? Of what use is this to the caterpillar?

3. Note the horn on the end of the caterpillar. Is it straight or curled? Is it on the head end? What color is it? Do you think it is of any use to the caterpillar? Do you think it is a sting? If there is no horn, is there an eye-spot on the last segment? What color is it? Can you think of any way in which this eye-spot protects the caterpillar?

4. Which segments of the caterpillar are the largest? When the creature is disturbed what position does it assume? How does it move? What noise does it make? Do you think this attitude scares away enemies? What position does it assume when resting? Do you think that it resembles the Egyptian Sphinx when resting?

5. How many true legs has this caterpillar? How does it use them when feeding? How many prolegs has it? How are these fleshy legs used? How are they armed to hold fast to the leaf or twig? Describe the hind or prop-leg. How is it used?

_A Myron caterpillar that has been parasitized. The white
objects upon it are the cocoons of the little grubs which feed
upon the fatty parts of the caterpillar._

Photo by M. V. Slingerland.]

6. Do you see the breathing pores or spiracles along the sides of the body? How many are there? How are they colored? How does the caterpillar breathe? Do you think it can breathe through its mouth?

7. How does the sphinx caterpillar grow? Watch your caterpillar and see it shed its skin. Where does the old skin break open? How does the new, soft skin look? Do the young caterpillars resemble the full-grown ones?

8. Describe how the caterpillar eats. Can you see the jaws move? Does it eat up the plant clean as it goes?

9. Have you ever found the sphinx caterpillar covered with whitish, oval objects? What are these? Does the caterpillar look plump or emaciated? Explain what these objects are and how they came to be there.

10. Where does the caterpillar go to change to a pupa? Does it make cocoons? How does the pupa look? Can you see the long tongue case, the wing cases, the antennæ cases?

_The Moth_

1. Where did you find this moth? Was it flying by daylight or in the dusk? How did its swift moving wings sound? Was it visiting flowers? What flowers? Where is the nectar in these flowers?

2. What is the shape of the moth’s body? Is it stout or slender? What colors has it? How is it marked?

3. The wings of which pair are longer? Sketch or describe the form of the front and the hind wings? Are the outer edges scalloped, notched or even? What colors are on the front wing? On the hind one? Are these colors harmonious and beautiful? Make a sketch of the moth in water-color.

Photo by M. V. Slingerland.]

4. What is the shape of the antennæ? Describe the eyes. Can you see the coiled tongue? Uncoil it with a pin and note how long it is. Why does this moth need such a long tongue?

5. From what flowers do the sphinx moths get nectar? How does the moth support itself when probing for nectar? Do you know any flowers which are dependent on the sphinx moths for carrying their pollen? How many kinds of sphinx moths do you know?

* * * * *

_Hurt no living thing:
Ladybird, nor butterfly,
Nor moth with dusty wing,
Nor cricket chirping cheerily,
Nor grasshopper so light of leap,
Nor dancing gnat, nor beetle fat,
Nor harmless worms that creep._
--CHRISTINA ROSSETTI.

THE CODLING MOTH

_Teacher’s Story_

It is difficult to decide which seems the most disturbed, the person who bites into an apple and uncovers a worm, or the worm which is uncovered. From our standpoint, there is nothing attractive about the worm which destroys the beauty and appetizing qualities of our fruit, but from the insect standpoint the codling caterpillar (which is not a worm at all), is not at all bad. When full-grown, it is about three-fourths of an inch long, and is likely to be flesh color, or even rose color, with brownish head; as a young larva, it has a number of darker rose spots on each segment and is whitish in color; the shield on the first segment behind the head, and that on the last segment of the body, are black. When full-grown, the apple worm is plump and lively; and while jerking angrily at being disturbed, we can see its true legs, one pair to each of the three segments of the body behind the head. These true legs have sharp, single claws. Behind these the third, fourth, fifth and sixth segments of the abdomen are each furnished with a pair of fleshy prolegs and the hind segment has a prop-leg. These fleshy legs are mere makeshifts on the part of the caterpillar for carrying the long body; since the three pairs of front legs are the ones from which develop the legs of the moth. The noticing of the legs of the codling moth is an important observation on the part of the pupils, since, by their presence, this insect may be distinguished from the young of the plum curculio, which is also found in apples but which is legless. The codling moth has twelve segments in the body, back of the head.

The codling larva usually enters the apple at the blossom end and tunnels down by the side of the core until it reaches the middle, before making its way out into the pulp. The larva weaves a web as it goes, but this is probably incidental, since many caterpillars spin silk as they go, “street yarn” our grandmothers might have called it. In this web are entangled the pellets of indigestible matter, making a very unsavory looking mass. The place of exit is usually circular, large enough to accommodate the body of the larva, and it leads out from a tunnel which may be a half inch or more in diameter beneath the rind. Often the larva makes the door sometime before it is ready to leave the apple, and plugs it with a mass of debris, fastened together with the silk. As it leaves the apple, the remnants of this plug may be seen streaming out of the opening. Often also, there is a mass of waste pellets pushed out by the young larva from its burrow, as it enters the apple; thus it injures the appearance of the apple, at both entrance and exit. If the apple has not received infection by lying next to another rotting apple, it first begins to rot around the burrow of the worm, especially near the place of exit.

The codling caterpillar injures the fruit in the following ways: The apples are likely to be stunted and fall early; the apples rot about the injured places and thus cannot be stored successfully; the apples thus injured look unattractive and, therefore, their market value is lessened; wormy apples, packed in barrels with others, rot and contaminate all the neighboring apples. This insect also attacks pears and sometimes peaches. It has been carefully estimated that every year the codling moth does three million dollars worth of injury to the apple and pear crops in New York State. Think of paying three million dollars a year for the sake of having wormy apples!

Photo by M. V. Slingerland.]

The larvæ usually leave the apples before winter. If the apples have fallen, they crawl up the tree and there make their cocoons beneath the loose bark; but if they leave the apples while they are on the trees, they spin silk and swing down. If carried into the storeroom or placed in barrels, they seek quarters in protected crevices. In fact, while they particularly like the loose bark of the apple trees, they are likely to build their cocoons on nearby fences or on brush, wherever they can find the needed protection. The cocoon is made of fine but rather rough silk which is spun from a gland opening near the mouth of the caterpillar; the cocoon is not beautiful although it is smooth inside. It is usually spun between a loose bit of bark and the body of the tree; but after making it, the insect seems in no hurry to change its condition and remains a quite lively caterpillar until spring. It is while the codling larvæ are in their winter quarters that our bird friends of the winter, the nuthatches, woodpeckers and chickadees, destroy them in great numbers, hunting eagerly for them in every crevice of the trees. It is therefore good policy for us to coax these birds to our orchards by placing beef fat on the branches and thus entice these little caterpillar hunters to visit the trees every day.

It is an interesting fact that the codling caterpillars, which make cocoons before August first, change immediately to pupæ which soon change to moths, and thus another generation gets in its work before the apples are harvested.

Photomicrograph by M. V. Slingerland.]

The codling moth is a beautiful little creature with delicate antennæ and a brown, mottled and banded body; its wings are graced by wavy bands of ashy and brown lines, and the tips of the front wings are dark brown with a pattern of gold bronze wrought into them; the hind wings are shiny brown with darker edges and little fringes. The moths issue in the spring and lay their eggs on the young apples just after the petals fall. The egg looks like a minute drop of dried milk and is laid on the side of the bud; but the little larva, soon after it is hatched, crawls to the blossom and finds entrance there; and it is therefore important that its first lunch should include a bit of arsenic and thus end its career before it fairly begins. The trees should be sprayed with some arsenical poison directly after the petals fall, and before the five lobes of the calyx close up around the stamens. If the trees are sprayed while blossoming, the pollen is washed away and the apples do not set; moreover, the bees which help us much in carrying pollen are killed. If the trees are sprayed directly after the calyx closes up around the stamens the poison does not lodge at the base of the stamens and the little rascals get into the apples without getting a dose. (See Lesson on the Apple).

Photo by M. V. Slingerland.]

LESSON LXXVI

THE CODLING MOTH

_Leading thought_--The codling moth is a tiny brown moth with bronze markings which lays its egg on the apple. The larva hatching from the egg enters the blossom end and feeds upon the pulp of the apple, injuring it greatly. After attaining its growth it leaves the apple and hides beneath the bark of the tree or in other protected places, and in the spring makes the cocoon from which the moth issues in time to lay eggs upon the young apples.

_The adult of the codling moth, showing the variations of its markings. The two larger are twice natural size._

Photo by M. V. Slingerland. ]

Photo by M. V. Slingerland.]

_Method_--The lesson should begin with a study of wormy apples, preferably in the fall when the worms are still within their burrows. After the pupils become familiar with the appearance of the insect and its methods of work, a prize of some sort might be offered for the one who will bring to school the greatest number of hibernating larvæ found in their winter quarters. Place these larvæ in a box with cheese-cloth tacked over its open side; place this box out of doors in a protected position. Examine the cocoons to find the pupæ about the last of April; after the pupæ appear, look for the moths in about five days.

It would be a very good idea for the pupils to prepare a Riker mount showing specimens of the moths, of the cocoons showing the cast pupa skin, and of the caterpillar in a homeopathic vial of alcohol; pictures illustrating the work of the insect may be added. The pictures should be drawn by the pupils, showing the wormy apple, both the outside and in section. The pupils can also sketch, from the pictures here given, the young apple when just in the right condition to spray, with a note explaining why.

_Observations_--1. Find an apple with a codling moth larva in it. How large is the worm? How does it act when disturbed?

2. What is the color of the caterpillar’s body? Its head?

3. How many segments are there in the body? How many of these bear legs? What is the difference in form between the three front pairs of legs and the others?

4. Look at a wormy apple. How can you tell it is wormy from the outside? Can you see where the worm entered the apple? Was the burrow large or small at first? Can you find an apple with a worm in it which has the door for exit made, but closed with waste matter? How is this matter fastened together? If the apple has no worm in it, can you see where it left the apple? Make a sketch or describe the evidence of the caterpillar’s progress through the apple. Do you find a web of silk in the wormy part? Why is this? Does the worm eat the seeds as well as the pulp of the apple?

5. Take a dozen rotting apples, how many of them are wormy? Do the parts of the apple injured by the worm begin to rot first? In how many ways does the codling moth injure the apple? Does it injure other fruits than apples?

6. How late in the fall do you find the codling larvæ in the apple? Where do these larvæ go when they leave the apple?

_Work to be done in March or early April_--Visit an orchard and look under the loose bark on old trees, or along protected sections of fences or brush piles and bring in all the cocoons you can find. Do not injure the cocoons by tearing them from the places where they are woven, but bring them in on bits of the bark or other material to which they are attached.

1. How does the cocoon look outside and inside? What is in the cocoon? Why was the cocoon made? When was it made?

2. Place the cocoons in a box covered with cheese-cloth and place the box out of doors where the contents can be frequently observed and make the following notes:

3. When does the larva change to the pupa? Describe the pupa. How does the cocoon look after the moth issues from it?

4. Describe the moth, noting color of head, thorax, body, front and hind wings?

5. If these moths were free to fly around the orchard, when and where would they lay their eggs?

6. When should the trees be sprayed to kill the young codling moth? With what should they be sprayed? Why should they not be sprayed during the blossoming period? Why not after the calyx closes?

Photo by M. V. Slingerland.]

7. How do the nuthatches, downy woodpeckers and chickadees help us in getting rid of the codling moth?

8. Write an essay on the life history of the codling moth, the damage done by it, and the best methods of keeping it in check.

_References_--The following bulletins from the U. S. Dept, of Agriculture: Farmers’ Bulletin 247, “The Control of the Codling Moth and Apple Scab;” Bulletin 35, New Series, Bureau of Entomology, “Report on the Codling Moth Investigations,” price 10 cents; Bulletin 41, “The Codling Moth,” 105 pages, 15 cents, by Special Field Agent, C. B. Simpson; Bulletin 68, Part VII, “Demonstration Spraying for the Codling Moth,” price 5 cents. The Spraying of Plants, Lodeman, Macmillan Company; Economic Entomology, Smith.

LEAF-MINERS

_Teacher’s Story_

“_And there’s never a leaf nor a blade too mean
To be some happy creature’s palace_.”
--LOWELL.

May not Lowell have had in mind, when he wrote these lines, the canny little creatures which find sustenance for their complete growth between the upper and lower surfaces of a leaf, which seems to us as thin as a sheet of paper. To most children, it seems quite incredible that there is anything between the upper and lower surfaces of a leaf, and this lesson should hinge on the fact that in every leaf, however thin, there are rows of cells containing the living substance of the leaf, with a wall above and a wall below to protect them. Some of the smaller insects have discovered this hidden treasure, which they mine while safely protected from sight, and thus make strange figures upon the leaves.

Comstock’s Manual.]

Among the most familiar of these are the serpentine mines, so called because the figure formed by the eating out of the green pulp of the leaf, curves like a serpent. These mines are made by the caterpillars of tiny moths, which have long fringes upon the hind wings. The life story of such a moth is as follows: The little moth, whose expanded wings measure scarcely a quarter of an inch across, lays an egg on the leaf; from this, there hatches a tiny caterpillar that soon eats its way into the midst of the leaf. In shape, the caterpillar is somewhat “square built,” being rather stocky and wide for its length; it feeds upon the juicy tissues of the leaf and divides, as it goes, the upper from the lower surface of the leaf; and it teaches us, if we choose to look, that these outer walls of the leaf are thin, colorless, and paper-like. We can trace the whole life history and wanderings of the little creature, from the time when, as small as a pin point, it began to feed, until it attained its full growth. As it increased in size, its appetite grew larger also, and these two forces working together naturally enlarged its house. When finally the little miner gets its growth, it makes a rather larger and more commodious room at the end of its mine, which to us looks like the head of the serpent; here it changes to a pupa, perhaps after nibbling a hole with its sharp little jaws, so that when it changes to a soft, fluffy little moth with mouth unfitted for biting, it is able to escape. In some species, the caterpillar comes out of the mine and goes into the ground to change to a pupa. By holding up to the light a leaf thus mined, we can see why this little chap was never obliged to clean house; it mined out a new room every day, and left the sweepings in the abandoned mine behind. Mines of this sort are often seen on the leaves of nasturtium, the smooth pigweed, columbine, and many other plants. There are mines of many shapes, each form being made by a different species of insect. Some flare suddenly from a point and are trumpet-shaped while some are mere blotches. The blotch mines are made, through the habits of the insect within them; it feeds around and around, instead of forging ahead, as is the case with the serpentine miners. The larvæ of beetles, flies and moths may mine leaves, each species having its own special food plant. Most of the smaller leaf mines are made by the caterpillars of the moths, which are fitly called the Tineina or Tineids. Most of these barely have a wing expanse that will reach a quarter of an inch and many are much smaller; they all have narrow wings, the hind wings being mere threads bordered with beautiful fringes. The specific names of these moths usually end in “ella;” thus, the one that mines in apple is _malifoliella_, the one in grain is _granella_. One of these little moths, _Gelechia pinifoliella_ lives the whole of its growing life in half of a pine needle. The moth lays the egg at about the middle of the needle, and the little caterpillar that hatches from it, gnaws its way directly into the heart of the needle; and there, as snug as snug can be, it lives and feeds until it is almost a quarter of an inch long, think of it! Many a time I have held up to the light a pine needle thus inhabited, and have seen the little miner race up and down its abode as if it knew that something was happening. When it finally attains its growth it makes wider the little door, through which it entered; it does this very neatly, the door is an even oval, and looks as if it were made with the use of dividers. After thus opening the door, the caterpillar changes to a little, long pupa, very close to its exit; and later it emerges, as an exquisite little moth with silvery bands on its narrow, brown wings, and a luxurious fringe on the edges of its narrow, hind wings and also on the outer hind edges of the front wings.

Photo by M. V. Slingerland.]

_The pine-needle leaf-miner. The mined leaves of pine natural
size. The caterpillar, pupa and moth of the leaf miner much
enlarged. The lines show actual size of insect._

Comstock’s Manual.]

The gross mines in the leaves of dock and beet are not pretty. The poor leaves are slitted, sometimes for their whole length, and soon turn brown and lie prone on the ground, or dangle pathetically from the stalk. These mines are made by the larvæ of a fly, and a whole family live in the same habitation. If we hold a leaf thus mined up to the light, while it is still green, we can see several of the larvæ working, each making a bag in the life substance of the leaf, and yet all joining together to make a great blister. The flies that do this mischief belong to the family _Anthomyinæ_; and there are several species which have the perturbing habit of mining the leaves of beets and spinach. It behooves those of us who are fond of these “greens,” as our New England ancestors called them, to hold every leaf up to the light before we put it into the skillet, lest we get more meat than vegetable in these viands. The flies, who thus take our greens ahead of us, are perhaps a little larger than house-flies, and are generally gray in color with the front of the head silver-white. These insects ought to teach us the value of clean culture in our gardens, since they also mine in the smooth pigweed.

_References_--Manual for the Study of Insects, Comstock.

LESSON LXXVII

LEAF-MINERS

_Leading thought_--The serpent-like markings and the blister-like blotches which we often see on leaves are made by the larvæ of insects which complete their growth by feeding upon the inner living substance of the leaf.

_Method_--The nasturtium leaf-miner is perhaps the most available for this lesson since it may be found in its mine in early September. However, the pupils should bring to the schoolroom all the leaves with mines in them, that they can find and study the different forms.

_Observations_--1. Sketch the leaf with the mine in it, showing the shape of the mine. What is the name of the plant on which the leaf grew?

2. Hold the leaf up to the light, can you see the insect within the mine? What is it doing? Are there more than one insect in the mine? Open the mine and see how the miner looks.

3. There are three general types of mines: Those that are long, curving lines called serpentine mines; those that begin small and flare out, called trumpet mines; and those that are blister-like called blotch mines. Which of these is the mine you are studying?

4. Study a serpentine mine. Note that where the little insect began to eat, the mine is small. Why does it widen from this point? What happened in the part which we call the serpent’s head?

5. Look closely with a lens and find if there is a break above the mine in the upper surface of the leaf or below the mine in the lower surface of the leaf. If the insect is no longer in the mine can you find where it escaped? Can you find a shed pupa-skin in the “serpent’s head?”

6. Why does an insect mine in a leaf? What does it find to eat? How is it protected from the birds or insects of prey while it is getting its growth?

7. Look on leaves of nasturtium, columbine, lamb’s quarters, dock and burdock, for serpentine mines. Are the mines on these different plants alike? Do you suppose they are made by the same insect?

8. Look on leaves of dock, burdock, beet and spinach for blotch mines. Are there more than one insect in these mines? If the insects are present, hold the leaf out to the light and watch them eat.

9. Look in the leaves of pitch or other thick leaved pines (not white pine), for pine needles which are yellow at the tip. Examine these for miners. If the miner is not within, can you find the little circular door by which it escaped? Would you think there was enough substance in a half a pine needle to support a little creature while it grew up?

10. If you find leaf-miners at work, do not pluck off the leaves being mined but cover each with a little bag of swiss muslin tied close about the petiole and thus capture the winged insect.

THE LEAF-ROLLERS

_Teacher’s Story_

If we look closely at sumac leaves before they are aflame from autumn’s torch, we find many of the leaflets rolled into little cornucopias fastened with silk. The silk is not in a web, like that of the spider, but the strands are twisted together, hundreds of threads combined in one strong cable, and these are fastened from roll to leaf, like tent ropes. If we look at the young basswoods, we find perhaps many of their leaves cut across, and the flap made into a roll and likewise fastened with silken ropes. The witch-hazel, which is a veritable insect tenement, also shows these rolls. In fact, we may find them upon the leaves of almost any species of tree or shrub, and each of these rolls has its own special maker or indweller. Each species of insect, which rolls the leaves, is limited to the species of plant on which it is found; and one of these caterpillars would sooner starve than take a mouthful from a leaf of any other plant. Some people think that insects will eat anything that comes in their way; but of all created animals, insects are the most fastidious as to their food.

_A leaf of basswood cut and rolled by the basswood leaf-roller._

Comstock. Manual.]

Some species of leaf-rollers unite several leaflets together, while others use a single leaf. In the case of the sumac leaf-roller, it begins in a single leaf; but in its later stages, it fastens together two or three of the terminal leaflets in order to gain more pasturage. The little silken tent ropes which hold the folded leaves are well worth study with a lens. They are made of hundreds of threads of the finest silk, woven from a gland opening near the lower lip of the caterpillar. The rope is always larger where it is attached to the leaf than at the center, because the caterpillar crisscrosses the threads in order to make the attachment to the leaf larger and firmer. Unroll a tent carefully, and you may see the fastenings used in an earlier stage, and may even find the first turned-down edge of the leaf. However, the center of a leaf roller’s habitation is usually very much eaten, for the whole reason for making its little house is that the soft-bodied caterpillar may eat its fill completely hidden from the eyes of birds or other animals. When it first hatches from the egg, it feeds for a short time, usually on the under side of the leaf; but when still so small that we can barely see it with the naked eye, it somehow manages to fold over itself one edge of the leaf and peg it down. The problem of how so small a creature is able to pull over and fold down or to make in a roll a stiff leaf is hard to solve. I, myself, believe it is done by making many threads, each a little more taut than the last. I have watched several species working, and the leaf comes slowly together as the caterpillar stretches its head and sways back and forth hundreds of times, fastening the silk first to one side and then to the other. Some observers believe that the caterpillar throws its weight upon the silk, in order to pull the leaf together; but in the case of the sumac leaf-roller, I am sure this is not true, as I have watched the process again and again under a lens, and could detect no signs of this method. Many of the caterpillars which make rolls, change to small moths known as Tortricids. This is a very large family, containing a vast number of species and not all of the members are leaf-rollers. These little moths have the front wings rather wide and more or less rectangular in outline. The entomologists have a pleasing fashion of ending the names of all of these moths with “ana;” the one that rolls the currant leaves is _Rosana_, the one on juniper is _Rutilana_, etc. Since many of the caterpillars of this family seek the ground to pupate and do not appear as moths until the following spring, it is somewhat difficult to study their complete life histories, unless one has well-made breeding cages with earth at the bottom; and even then it is difficult to keep them under natural conditions, since in an ordinary living room the insects dry up and do not mature.

LESSON LXXVIII

THE LEAF-ROLLERS

_Leading thought_--There are many kinds of insects which roll the leaves of trees and plants into tents, in which they dwell and feed during their early stages.

_Method_--This is an excellent lesson for early autumn when the pupils may find many of these rolled leaves, which they may bring to the schoolroom, and which will give material for the lesson. The rolls are found plentifully on sumac, basswood and witch-hazel.

_Observations_--1. What is the name of the trees and shrubs from which these rolled leaves which you have collected were taken?

2. Are more than one leaf or leaflet used in making the roll?

3. Is the leaf rolled crosswise or lengthwise? How large is the tube thus made?

4. Is the nest in the shape of a tube, or are several leaves fastened together, making a box-shaped nest?

5. How is the roll made fast? Examine the little silken ropes with a lens and describe one of them. Is it wider where it is attached to the leaf than at the middle? Why?

6. How many of these tent ropes are there which make fast the roll? Unroll a leaf carefully and see if you can find signs of the tent ropes that fastened the roll together when it was smaller. Can you find where it began?

7. As you unroll the leaves what do you see at the center? Has the leaf been eaten? Can you discover the reason why the caterpillar made this roll?

8. How do you think a caterpillar manages to roll a leaf so successfully? Where is the spinning gland of a caterpillar? How does the insect act when spinning threads back and forth when rolling the leaf? What sort of insect does the caterpillar which rolls the leaf change into? Do you suppose that the same kind of caterpillars makes the rolls on two different species of trees?

9. In July or early August get some of the rolls with the caterpillars in them, unroll a nest, take the caterpillar out and put it on a fresh leaf of the same kind of tree or shrub on which you found it, and watch it make its roll.

_Supplementary reading_--“A Dweller in Tents” and “A Little Nomad,” in Ways of the Six-Footed.

_The spiny oak-gall._
_The pointed bullet-gall on oak twigs._
_A cluster of galls on midrib of oak leaf._
_The acorn plum-gall._

Photo by L. H. Weld.]

THE GALL-DWELLERS

_He retired to his chamber, took his lamp, and summoned
the genius as usual. “Genius,” said he, “build me a palace
near the sultan’s, fit for the reception of my spouse, the
princess; but instead of stone, let the walls be formed of
massy gold and silver, laid in alternate rows; and let the
interstices be enriched with diamonds and emeralds. The palace
must have a delightful garden, planted with aromatic shrubs
and plants, bearing the most delicious fruits and beautiful
flowers. But, in particular, let there be an immense treasure
of gold and silver coin. The palace, moreover, must be well
provided with offices, storehouses, and stables full of
the finest horses, and attended by equerries, grooms, and
hunting equipage.” By the dawn of the ensuing morning, the
genius presented himself to Aladdin, and said, “Sir, your
palace is finished; come and see if it accords with your
wishes.”_
--ARABIAN NIGHTS ENTERTAINMENTS.

Although Aladdin is out of fashion, we still have houses of magic that are even more wonderful than that produced by his resourceful lamp. These houses are built through an occult partnership between insects and plant tissues; and no one understands just how they are made, although we are beginning to understand a little concerning the reasons for the growth. These houses are called galls and are thus well named, since they grow because of an irritation to the plant caused by the insect.

There are many forms of these gall-dwellings, and they may grow upon the root, branch, leaf, blossom, or fruit. The miraculous thing about them is that each kind of insect builds its magical house on a certain part of a certain species of tree or plant; and the house is always of a certain definite form on the outside and of a certain particular pattern within. Many widely differing species of insects are gall-makers; and he who is skilled in gall lore knows, when he looks at the outside of the house, just what insect dwells within it.

Comstock’s Manual.]

We may take the history of the common oak apple, as an example. A little, four-winged, fly-like creature lays its eggs, early in the season, on the leaf of the scarlet oak. As soon as the larva hatches, it begins to eat into the substance of one of the leaf veins. As it eats, it discharges through its mouth into the tissues of the leaf, a substance which is secreted from glands within its body. Immediately the building of the house commences; out around the little creature grow radiating vegetable fibers, showing by their position plainly that the grub is the center of all of this new growth; meanwhile, a smooth, thin covering completely encloses the globular house; larger and larger grows the house until we are accustomed to call it an oak apple, so large is it. The little chap inside is surely content and happy, for it is protected from the sight of all of its enemies, and it finds the walls of its house the best of food. It is comparable to a boy living in the middle of a giant sponge cake, and who when hungry would naturally eat out a larger cave in the heart of the cake. After the inmate of the oak apple completes its growth, it changes to a pupa and finally comes out into the world a tiny four-winged fly, scarcely a quarter of an inch in length.

The story of the willow cone-gall is quite different. A little gnat lays her eggs on the tip of the bud of a twig; as soon as the grub hatches and begins to eat, the growth of the twig is arrested, the leaves are stunted until they are mere scales and are obliged to overlap in rows around the little inmate, thus making for it a cone-shaped house which is very thoroughly shingled. The inhabitant of this gall is a hospitable little fellow, and his house shelters and feeds many other insect guests. He does not pay any attention to them, being a recluse in his own cell, but he civilly allows them to take care of themselves in his domain, and feed upon the walls of his house. He stays in his snug home all winter and comes out in the spring a tiny, two-winged fly.

Photo by Verne Morton.]

Photo by M. V Slingerland.]