Chapter XXV: Part II: Animal Life (18)

The dragon-fly nymphs are the ogres of the pond or stream. To anyone unused to them and their ways in the aquarium, there is a surprise in store, so ferocious are they in their attacks upon creatures twice their size. The dragon-fly’s eggs are laid in the water; in some instances they are simply dropped and sink to the bottom; but in the case of damsel-flies, the mother punctures the stems of aquatic plants and places the eggs within them. The nymph in no wise resembles the parent dragon-fly. It is a dingy little creature, with six queer, spider-like legs and no wings; although there are four little wing-pads extending down its back, which encase the growing wings. It may remain hidden in the rubbish at the bottom of the pond or may cling to water weeds at the sides, for different species have different habits. But in them all we find a most amazing lower lip. This is so large that it covers the lower part of the face like a mask, and when folded back reaches down between the front legs. It is in reality a grappling organ with hooks and spines for holding prey; it is hinged in such a manner that it can be thrust out far beyond the head to seize some insect, unsuspecting of danger. These nymphs move so slowly and look so much like their background, that they are always practically in ambush awaiting their victims.

Outdoor Studies, Needham.]

The breathing of the dragon-fly nymphs is peculiar; there is an enlargement of the rear end of the alimentary canal, in the walls of which tracheæ or breathing tubes extend in all directions. The nymph draws water into this cavity and then expels it, thus bathing the tracheæ with the air mixed with water and purifying the air within them. Expelling the water so forcibly, propels the nymph ahead, so this act serves as a method of swimming as well as of breathing. Damsel-fly larvæ, on the other hand, have at the rear end of the body, three long, plate-like gills, each ramified with tracheæ.

Seen from the side, showing the position of the great lower lip when folded beneath the head.

From Outdoor Studies, Needham.]

Nymphs grow by shedding the skin as fast as it becomes too small; and when finally ready to emerge, they crawl up on some object out of the water, and molt for the last time, and are thereafter swift creatures of the air.

_References_--American Insects, Kellogg. Comstock’s Manual.

LESSON LXXXV

THE DRAGON-FLIES AND DAMSEL-FLIES

_Leading thought_--The dragon-flies are among the swiftest of all winged creatures and their rapid, darting flight enables them to hawk their prey, which consists of other flying insects. Their first stages are passed in the bottoms of ponds where they feed voraciously on aquatic creatures. The dragon-flies are beneficial to us because, when very young and when full grown, they feed largely upon mosquitoes.

_Method_--The work of observing the habits of adult dragon-flies should be largely done in the field during late summer and early autumn. The points for observation should be given the pupils for summer vacation use, and the results placed in the field note-book.

The nymphs may be studied in the spring, when getting material for the aquarium. April and May are the best months for securing them. They are collected by using a dip-net, and are found in the bottoms of reedy ponds or along the edges of slow-flowing streams. These nymphs are so voracious that they cannot be trusted in the aquarium with other insects; each must be kept by itself. They may be fed by placing other water insects in the aquarium with them or by giving them pieces of fresh meat. In the latter case, tie the meat to a thread so that it may be removed after a few hours, if not eaten, since it soon renders the water foul.

The dragon-fly aquarium should have sand at the bottom and some water weeds planted in it, and there should be some object in it which extends above the surface of the water which the nymphs, when ready to change to adults, can climb upon while they are shedding the last nymphal skin, and spreading their new wings.

_Observations on the young of dragon-flies_--1. Where did you find these insects? Were they at the bottom of the pond or along the edges among the water weeds?

2. Are there any plume-like gills at the end of the body? If so, how many? Are these plate-like gills used for swimming? If there are three of these, which is the longer? Do you know whether the nymphs with these long gills develop into dragon or into damsel-flies?

Outdoor Studies, Needham.]

Outdoor Studies, Needham.]

3. If there are no plume-like gills at the end of the body, how do the insects move? Can they swim? What is the general color of the body? Explain how this color protects them from observation? What enemies does it protect them from?

4. Are the eyes large? Can you see the little wing-pads on the back in which the wings are developing? Are the antennæ long?

5. Observe how the nymphs of both dragon and damsel-flies seize their prey. Describe the great lower lip when extended for prey. How does it look when folded up?

6. Can you see how a nymph without the plume-like gills breathes? Notice if the water is drawn into the rear end of the body and then expelled. Does this process help the insect in swimming?

7. When the dragon or damsel-fly nymph has reached its full growth, where does it go to change to the winged form? How does this change take place? Look on the rushes and reeds along the pond margin, and see if you can find the empty nymph skins from which the adults emerged. Where is the opening in them?

_Observations on the adult dragon-flies_--1. Catch a dragon-fly, place it under a tumbler and see how it is fitted for life in the air. Which is the widest part of its body? Note the size of the eyes compared with the remainder of the head. Do they almost meet at the top of the head? How far do they extend down the sides of the head? Why does the dragon-fly need such large eyes? Why does a creature with such eyes not need long antennæ? Can you see the dragon-fly’s antennæ? Look with a lens at the little, swollen triangle between the place where the two eyes join and the forehead; can you see the little, simple eyes? Can you see the mouth-parts?

2. Next to the head, which is the widest and strongest part of the body? Why does the thorax need to be so big and strong? Study the wings. How do the hind wings differ in shape from the front wings? How is the thin membrane of the wings made strong? Are the wings spotted or colored? If so, how? Can you see if the wings are folded along the front edges? Does this give strength to the part of the wing which cuts the air? Take a piece of writing paper and see how easily it bends; fold it two or three times like a fan and note how much stiffer it is. Is it this principle which strengthens the dragon-fly’s wings? Why do these wings need to be strong?

3. Is the dragon-fly’s abdomen as wide as the front part of the body? What help is it to the insect when flying to have such a long abdomen?

_Outline for field notes_--Go to a pond or sluggish stream when the sun is shining, preferably at midday, and note as far as possible the following things:

1. Do you see dragon-flies darting over the pond? Describe their flight. They are hunting flies and mosquitoes and other insects on the wing; note how they do it. If the sky becomes cloudy, can you see the dragon-flies hunting? In looking over a pond where there are many dragon-flies darting about, do the larger species fly higher than the smaller ones?

2. Note the way the dragon-flies hold their wings when they are resting. Do they rest with their wings folded together over the abdomen or are they extended out at an angle to the abdomen? Do you know how this difference in attitude of resting determines one difference between the damsel-flies and the dragon-flies?

3. The damsel-flies are those which hold their wings folded above the back when resting. Are these as large and strong-bodied as the dragon-flies? Are their bodies more brilliantly colored? How does the shape of the head and eyes differ from those of the dragon-flies? How many different colored damsel-flies can you find?

4. Do you see some dragon-flies dipping down in the water as they fly? If so, they are laying their eggs. Note if you find others clinging to reeds or other plants with the abdomen thrust below the surface of the water. If so, these are inserting their eggs into the stem of the plant.

_Supplementary reading_--Outdoor Studies, Needham, p. 54; “The Dragon of Lagunita” in Insect Stories, Kellogg.

THE CADDIS-WORMS AND THE CADDIS-FLIES

_Teacher’s Story_

People are to be pitied who have never tried to fathom the mysteries of the bottom of brook or pond. Just to lie flat, face downward, and watch for a time all that happens down there in that water world, is far more interesting than witnessing any play ever given at matinee. At first one sees nothing, since all the swift-moving creatures have whisked out of sight, because they have learned to be shy of moving shadows; but soon the crayfish thrusts out his boxing gloves from some crevice, then a school of tiny minnows “stay their wavy bodies ’gainst the stream;” and then something strange happens! A bit of rubbish on the bottom of the brook walks off. Perhaps it is a dream, or we are under the enchantment of the water witches! But no, there goes another, and now a little bundle of sand and pebbles takes unto itself legs. These mysteries can only be solved with a dip-net and a pail half filled with water, in which we may carry home the treasure trove.

When we finally lodge our catch in the aquarium jar, our mysterious moving sticks and stones resolve themselves into little houses built in various fashions, and each containing one inmate. Some of the houses are made of sticks fastened together lengthwise; some are built like log cabins, crosswise; some consist simply of a hollow stem cut a convenient length; and some are made of sand and pebbles, and one, the liveliest of all, is a little tube made of bits of rubbish and silk spun in a spiral, making a little cornucopia.

Photo by J. T. Lloyd.]

On the whole, the species which live in the log cabins are the most convenient to study. Whatever the shape of the case or house, it has a very tough lining of silk, which is smooth within, and forms the framework to which the sticks and stones are fastened. These little dwellings always have a front door and a back door. Out of the front door may protrude the dark-colored head followed by two dark segments and six perfectly active legs, the front pair being so much shorter than the other two pairs that they look almost like mouth palpi. In time of utter peace, more of the little hermit is thrust out and we see the hind segment of the thorax which is whitish, and behind this the abdomen of nine segments. At the sides of the abdomen, and apparently between the segments, are little tassels of short, white thread-like gills. These are filled with air, impure from contact with the blood, and which exchanges its impurities speedily for the oxygen from the air which is mixed with the water. Water is kept flowing in at the front door of the cabin, over the gills and out at the back door, by the rhythmic movement of the body of the little hermit, and thus a supply of oxygen is steadily maintained.

Photo by J. T. Lloyd.]

The caddis-worm is not grown fast to its case as is the snail to its shell. If we hold down with forceps a case in which the occupant is wrong side up, after a few struggles to turn itself over, case and all, it will turn over within the case. It keeps its hold upon the case by two forward-curving hooks, one on each side of the tip of the rear segment. These hooks are inserted in the tough silk and hold fast. It also has on top of the first segment of the abdomen a tubercle, which may be extended at will; this helps to brace the larva in its stronghold, and also permits the water to flow freely around the insect. So the little hermit is entrenched in its cell at both ends. When the log-cabin species wishes to swim, it pushes almost its entire body out of the case, thrusts back the head, spreads the legs wide apart, and then doubles up, thus moving through the water spasmodically, in a manner that reminds us of the crayfish’s swimming except that the caddis-worm goes head first. This log cabin species can turn its case over dexterously by movements of its legs.

Showing gills and the hooks on the last segment for holding fast to the case.]

The front legs of the caddis-worm are so much shorter than the other two pairs that they look like palpi, and their use is to hold close to the jaws bits of food, which are being eaten. The other legs are used for this too if the little legs cannot manage it; perhaps also these short front legs help hold the bits of building material in place while the web is woven to hold it there. The caddis-worm, like the true caterpillars, has the opening of the silk gland near the lower lip. The food of most caddis-worms is vegetable, usually the various species of water plants; but there are some species which are carnivorous, like the net-builder, which is a fisherman.

Photo by J. T. Lloyd.]

The caddis-worm case protects its inmate in two ways: First, from the sight of the enemy, and second, from its jaws. A fish comes along and sees a nice white worm and darts after it, only to find a bundle of unappetizing sticks where the worm was. All of the hungry predatory creatures of the pond and stream would be glad to get the caddis-worm, if they knew where it went. Sometimes caddis-worm cases have been found in the stomachs of fishes; perhaps they serve as fish breakfast-food.

Photo by J. T. Lloyd.]

While it is difficult to see the exact operation of building the caddis-worm house, the general proceeding may be readily observed. Take a vigorous half-grown larva, tear off part of the sticks and bits of leaves that make the log cabin, and then place the little builder in a tumbler with half an inch of water at the bottom, in which are many bright flower petals cut into strips, fit for caddis lumber. In a few hours the little house will look like a blossom with several rows of bright petals set around its doorway.

Photomicrograph by J. T. Lloyd.]

When the caddis-worm gets ready to pupate, it fastens its case to some object in the water and then closes its front and back doors. Different species accomplish this in different ways; some spin and fasten a silken covering over the doors; often this is in the form of a pretty grating; others simply fasten the material of which the case is made across the door. But though the door be shut, it is so arranged as to allow the water to flow through and to bring oxygen to the thread-like gills, which are on the pupæ as well as on the larvæ. When ready to emerge, the pupa crawls out of its case and climbs to some object above the water, sheds its pupa skin, and the adult insect flies off. In some species, living in swift water, the adult issues directly from the water, its wings expanding as soon as touched by the air.

Photo by J. T. Lloyd.]

Caddis-flies are familiar to us all even if we do not know them by name. They are night fliers and flame worshippers. Their parchment-like or leathery wings are folded like a roof over the back, and from the side the caddis-fly appears as an elongated triangle with unequal sides. The front wings are long and the hind ones shorter and wider; the antennæ are long and threadlike and always waving about for impressions; the eyes are round and beadlike; the tarsi, or feet, are long and these insects have an awkward way of walking on the entire tarsus which gives them an appearance of kneeling. Most of the species are dull-colored, brownish or gray, the entire insect often being of one color. Caddis-flies would not be so fond of burning themselves in lamps if they had the human sense of smell, for the stench they make when scorching is nauseating. The mother caddis-flies lay their eggs in the water. Perhaps some species drop the eggs in when hovering above, but in some cases the insect must make a diving bell of her wings and go down into the water to place her eggs securely. The wings are covered with hairs and not with scales, and therefore they are better fitted for diving than would be those of the moth. I have seen caddis-flies swim vigorously.

_References_--Aquatic Insects, Miall; Manual for the Study of Insects, Comstock.

Photo by J. T. Lloyd.]

Comstock’s Manual.]

LESSON LXXXVI

THE CADDIS-WORMS AND CADDIS-FLIES

_Leading thought_--The caddis-worms build around themselves little houses out of bits of sticks, leaves or stones. They crawl about on the bottom of the pond or stream, protected from sight, and able to withdraw into their houses when attacked. The adult of the caddis-worm is a winged moth-like creature which comes in numbers to the light at night.

_Method_--With a dip-net the caddis-worms may be captured and then may be placed in the school aquarium. Duckweed and other water plants should be kept growing in the aquarium. The log cabin species is best for this study, because it lives in stagnant water and will therefore thrive in an aquarium.

_Observations_--1. Where do you find the caddis-worms? Can you see them easily on the bottom of the stream or pond? Why?

2. Of what are the caddis-worm houses made? How many kinds have you ever found? How many kinds of materials can you find on one case? Describe one as exactly as possible. Find an empty case and describe it inside. Why is it so smooth inside? How is it made so smooth? Are all the cases the same size?

3. What does the caddis-worm do when it wishes to walk around? What is the color of the head and the two segments back of it? What is the color of the body? Why is this difference of color between the head and body protective? Is the caddis-worm grown fast to its case, as the turtle is to its shell?

4. Note the legs. Which is the shorter pair? How many pairs? What is the use of the legs so much shorter than the others? If the caddis-worm case happens to be wrong side up, how does it turn over?

5. When it wishes to come to the surface or swim, what does the caddis-worm do? When reaching far out of its case does it ever lose its hold? How does it hold on? Pull the caddis-worm out of its case and see the hooks at the end of the body with which it holds fast.

6. How does the caddis-worm breathe? When it reaches far out of its case, note the breathing gills. Describe them. Can you see how many there are on the segments? How is the blood purified through these gills?

7. What are the caddis-worm’s enemies? How does it escape them? Touch one when it is walking, what does it do?

8. On top of the first segment of the abdomen is a tubercle. Do you suppose that this helps to hold the caddis-worm in its case?

9. What does the caddis-worm eat? Describe how it acts when eating.

10. How does the caddis-worm build its case? Watch one when it makes an addition to its case, and describe all that you can see.

11. Can you find any of the cases with the front and back doors closed? How are they closed? Open one and see if there is a pupa within it. Can you see the growing wings, antennæ and legs? Has it breathing filaments like the larva? Cover the aquarium with mosquito netting so as to get all the moths which emerge. See if you can discover how the pupa changes into a caddis-fly.

12. How does the caddis-fly fold its wings? What is the general shape of the insect when seen from the side with wings closed? What is the texture of the wings? How many wings are there? Which pair is the longer?

13. Describe the eyes. The antennæ. Does the caddis-fly walk on its toes, or on its complete foot?

14. Examine the moths which come around the lights at night in the spring and summer. Can you tell the caddis-flies from other insects? Do they dash into the light? Do they seem anxious to burn themselves?

_Supplementary reading_--“A Little Fisherman,” Ways of the Six-Footed, Comstock.

Comstock’s Manual.]

_Little brook, so simple so unassuming--and yet how many things
love thee!_

_Lo! Sun and Moon look down and glass themselves in thy
waters._

_And the trout balances itself hour-long against the stream,
watching for its prey; or retires under a stone to rest._

_And the water-rats nibble off the willow leaves and carry
them below the wave to their nests--or sit on a dry stone to
trim their whiskers._

_And the May-fly practices for the millionth time the miracle
of the resurrection, floating up an ungainly grub from the mud
below, and in an instant, in the twinkling of an eye (even
from the jaws of the baffled trout) emerging, an aerial fairy
with pearl-green wings._

_And the caddis-fly from its quaint disguise likewise emerges._

_And the prick-eared earth-people, the rabbits, in the stillness
of early morning play beside thee undisturbed, while the level
sunbeams yet grope through the dewy grass._

_And the squirrel on a tree-root--its tail stretched far
behind--leans forward to kiss thee,_

_Little brook, for so many things love thee._
EDWARD CARPENTER.

THE APHIDS, OR PLANT-LICE

_Teacher’s Story_

I know of no more diverting occupation than watching a colony of aphids through a lens; these insects are the most helpless and amiable little ninnies in the whole insect world; and they look the part, probably because their eyes, so large and wide apart, seem so innocent and wondering. The usual color of aphids is green. As they feed upon leaves, this color protects them from sight; but there are many species which are otherwise colored, and some have most bizarre and striking ornamentations. In looking along an infested leaf stalk, we see them in all stages and positions. One may have thrust its beak to the hilt in a plant stem, and is so satisfied and absorbed in sucking the juice that its hind feet are lifted high in the air and its antennæ curved backward, making altogether a gesture which seems an adequate expression of bliss; another may conclude to seek a new well, and pulls up its sucking tube, folding it back underneath the body so it will be out of the way, and walks off slowly on its six rather stiff legs; when thus moving, it thrusts the antennæ forward, patting its pathway to insure safety. Perhaps this pathway may lead over other aphids which are feeding, but this does not deter the traveler nor turn it aside; over the backs of the obstructionists it crawls, at which the disturbed ones kick the intruder with both hind legs; it is not a vicious kick but a push rather, which says, “This seat reserved, please!” It is comical to see a row of them sucking a plant stem for “dear life,” the heads all in the same direction, and they packed in and around each other as if there were no other plants in the world to give them room, the little ones wedged in between the big ones, until sometimes some of them are obliged to rest their hind legs on the antennæ of the neighbors next behind.

Photo by Slingerland.]

Aphids are born for food for other creatures--they are simply little machines for making sap into honey-dew, which they produce from the alimentary canal for the delectation of ants; they are, in fact, merely little animated drops of sap on legs. How helpless they are when attacked by any one of their many enemies! All they do, when they are seized, is to claw the air with their six impotent legs and two antennæ, keeping up this performance as long as there is left a leg, and apparently to the very last, never realizing “what is doing.” But they are not without means of defence; those two little tubes at the end of the body are not for ornament nor for producing honey-dew for the ants, but for secreting at their tips a globule of waxy substance meant to smear the eyes of the attacking insect. I once saw an aphid perform this act, when confronted by a baby spider; a drop of yellow liquid oozed out of one tube, and the aphid almost stood on its head in order to thrust this offensive globule directly into the face of the spider--the whole performance reminding me of a boy who shakes his clenched fist in his opponent’s face and says, “Smell of that!” The spider beat a hasty retreat.

A German scientist, Mr. Busgen, discovered that a plant-louse smeared the eyes and jaws of its enemy, the aphis-lion, with this wax which dried as soon as applied. In action it was something like throwing a basin of paste at the head of the attacking party; the aphis-lion thus treated, was obliged to stop and clean itself before it could go on with its hunt, and the aphid walked off in safety. The aphids surely need this protection because they have two fierce enemies, the larvæ of the aphis-lions and of the ladybirds. They are also the victims of parasitic insects; a tiny four-winged “fly” lays an egg within an aphid; the larva hatching from it feeds upon the inner portions of the aphid, causing it to swell as if afflicted with dropsy. Later the aphid dies, and the interloper with malicious impertinence cuts a neat circular door in the poor aphid’s skeleton skin and issues from it a full fledged insect.

The aphids are not without their resources to meet the exigencies of their lives in colonies. There are several distinct forms in each species, and they seem to be needed for the general good. During the summer, we find most of the aphids on plants are without wings; these are females which give birth to living young and do not lay eggs. They do this until the plant is overstocked and the food supply seems to be giving out, then another form is produced which has four wings. These fly away to some other plant and start a colony there; but at the approach of cold weather, or if the food plants give out, there are male and female individuals developed, the females being always wingless, and it is their office to lay the eggs which shall last during the long winter months, when the living aphids must die for lack of food plants. The next spring each winter-egg hatches into a female which we call the “stem mother” since she with her descendants will populate the entire plant.

Plant-lice vary in their habits. Some live in the ground on the roots of plants and are very destructive; but the greater number of species live on the foliage of plants and are very fond of the young, tender leaves and thus do great damage. Some aphids have their bodies covered with white powder or with tiny fringes, which give them the appearance of being covered with cotton.

The aphids injuring our flowers and plants may be killed by spraying them with soapsuds made in the proportion of one-quarter pound of ivory soap to one gallon of water. The spraying must be done very thoroughly so as to reach all the aphids hidden on the stems and beneath the leaves. It should be repeated every three days until the aphids are destroyed.

LESSON LXXXVII

THE APHIDS, OR PLANT-LICE

_Leading thought_--Aphids have the mouth in the form of a sucking tube which is thrust into the stems and leaves of plants; through it the plant juices are drawn for nourishment. Aphids are the source of honey-dew of which ants are fond.

_Method_--Bring into the schoolroom a plant infested with aphids, place the stem in water and let the pupils examine the insects through the lens.

_Observations_--1. How are the aphids settled on the leaf? Are their heads in the same direction? What are they doing?

2. Touch one and make it move along. What does it do in order to leave its place? What does it do with its sucking tube as it walks off? On what part of the plant was it feeding? Why does not Paris green when applied to the leaves of plants kill aphids?

3. Describe an aphid, including its eyes, antennæ, legs and tubes upon the back. Does its color protect it from observation?

4. Can you see cast skins of aphids on the plant? Why does an aphid have to shed its skin?

5. Are all the aphids on a plant wingless? When a plant becomes dry are there, after several days, more winged aphids? Why do the aphids need wings?

6. Do you know what honey-dew is? Have you ever seen it upon the leaf? How is honey-dew made by the aphids? Does it come from the tubes on their back? What insects feed upon this honey-dew?

7. What enemies have the aphids?

8. What damage do aphids do to plants? How can you clean plants of plant-lice?

* * * * *

_I saw it_ (_an ant_), _at first, pass, without stopping, some
aphids which it did not however disturb. It shortly after
stationed itself near one of the smallest, and appeared to
caress it, by touching the extremity of its body, alternately
with its antennæ, with an extremely rapid movement. I saw,
with much surprise, the fluid proceed from the body of the
aphid, and the ant take it in its mouth. Its antennæ were
afterwards directed to a much larger aphid than the first,
which, on being caressed after the same manner, discharged
the nourishing fluid in greater quantity, which the ant
immediately swallowed: it then passed to a third which it
caressed, like the preceding, by giving it several gentle
blows, with the antennæ, on the posterior extremity of the
body; and the liquid was ejected at the same moment, and the
ant lapped it up._
PIERRE HUBER, 1810.

THE ANT-LION

_Teacher’s Story_

A child is thrilled with fairy stories of ogres in their dens, with the bones of their victims strewn around. The ants have real ogres, but luckily, they do not know about it and so cannot suffer from agonizing fears. The ant ogres seem to have depended upon the fact that the ant is so absorbed in her work that she carries her booty up hill and down dale with small regard for the topography of the country. Thus they build their pits, with instinctive faith that they will some day be entered by these creatures, obsessed by industry and careless of what lies in the path. The pits vary with the size of the ogre at the bottom; there are as many sized pits as are beds in the story of Golden Locks and the bears; often the pits are not more than an inch across, or even less, while others are two inches in diameter. They are always made in sandy or crumbly soil and in a place protected from wind and rain; they vary in depth in proportion to their width, for the slope is always as steep as the soil will stand without slipping.

All that can be seen of the ogre at the bottom, is a pair of long, curved jaws, looking innocent enough at the very center of the pit. If we dig the creature out, we find it a comical looking insect. It is humpbacked, with a big, spindle-shaped abdomen; from its great awkward body projects a flat, sneaking looking head, armed in front with the sickle jaws which are spiny and bristly near the base, and smooth, sharp and curved at the tip. The strange thing about these jaws is that they lead directly to the throat, since the ant-lion has no mouth. Each jaw is made up of two pieces which are grooved where they join and thus form a tube with a hole in the tip through which the industrious blood of the ants can be sucked; not only do the sharp sickle points hold the victim, but there are three teeth along the side of each jaw to help with this. The two front pairs of legs are small and spiny; the hind legs are strong and peculiarly twisted, and have a sharp spikelike claw at the end, which is so arranged as to push the insect backward vigorously if occasion requires; in fact, the ant-lion in walking about, moves more naturally backward than forward because of the peculiar structure of his legs.

Comstock’s Manual.]

Having studied the ogre, we can see better how he manages to trap his victim. As the ant goes scurrying along, she rushes over the edge of the pit and at once begins to slide downward; she is frightened and struggles to get back; just then a jet of sand, aimed well from the bottom of the pit, hits her and knocks her back. She still struggles, and there follows a fusillade of sand jets, each hitting her from above and knocking her down to the fatal center where the sickle jaws await her and are promptly thrust into her; if she is large and still struggles, the big, unwieldy body of the ogre, buried in the sand, anchors him fast and his peculiar, crooked hind legs push his body backward in this strange tug of war; thus, the ant-ogre is not dragged out of his den by the struggles of the ant, and soon the loss of blood weakens her and she shrivels up.

The secret of the jets of sand, lies in the flat head of the ogre; if we look at it regarding it as a shovel, we can see that it is well fitted for its purpose; for it is a shovel with a strong mechanism working it. In fact, the whole pit is dug with this shovel head. Wonderful stories are told about the way that ant-lions dig their pits, marking out the outer margin in a circle, and working inward. However, our common ant-lion of the East simply digs down into the sand and flips the sand out until it makes a pit. If an ant-lion can be caught and put in a jar of sand it will soon make its pit, and the process may be noted carefully.

There is one quality in the ogre which merits praise, and that is his patience. There he lies in his hole for days or perhaps weeks, with nothing to eat and no ant coming that way; so when we see an absent-minded ant scrambling over into the pit, let us think of the empty stomach of this patient little engineer which has constructed his pit with such accuracy and so much labor. So precarious is the living picked up by the ant-lions, that it may require one, two or three years to bring one to maturity. At that time it makes a perfectly globular cocoon of silk and sand, the size of a large pea, and within it, changes to a pupa; and when finally ready to emerge, the pupa pushes itself part way out of the cocoon and the skin is shed and left at the cocoon door. The adult resembles a small dragon-fly; it has large net-veined wings and is a most graceful insect, as different as can be from the humpbacked ogre which it once was--a transformation quite as marvelous as that which occurred in Beauty and the Beast. Throughout the Middle West, the ant-lion in its pit is called the “doodle-bug.”

_Reference_--Manual for Study of Insects, Comstock.

LESSON LXXXVIII

THE ANT-LION

_Leading thought_--The ant-lion, or “doodle-bug” makes a little pit in the sand with very steep sides, and hidden at the bottom of it, waits for ants to tumble in to be seized by its waiting jaws. Later the ant-lion changes to a beautiful insect with gauzy wings, resembling a small dragon-fly.

_Method_--The pupils should see the ant-lion pits in their natural situations, but the insects may be studied in the schoolroom. Some of the ant-lions may be dug out of their pits and placed in a dish of sand. They will soon make their pits, and may be watched during this interesting process. It is hardly advisable to try to rear these insects, as they may require two or three years for development.

_Observations_--1. Where were the ant-lion pits out of doors? Were they in a windy place? Were they in a place protected from storms? In what kind of soil were they made?

2. Measure one of the pits. How broad across, and how deep? Are all the pits of the same size? Why?

3. What can you see as you look down into the ant-lion’s pit? Roll a tiny pebble in and see what happens? Watch until an ant comes hurrying along and slips into the pit. What happens then? As she struggles to get out how is she knocked back in? What happens to her if she falls to the bottom?

4. Take a trowel and dig out the doodle-bug. What is the shape of its body? What part of the insect did you see at the bottom of the pit? Do you know that these great sickle-shaped jaws are hollow tubes for sucking blood? Does the ant-lion eat anything except the blood of its victim?

5. Can you see that the ant-lion moves backward more easily than forward? How are its hind legs formed to help push it backward? How does this help the ant-lion in holding its prey? How does the big awkward body of the ant-lion help to hold it in place at the bottom of the pit when it seizes an ant in its jaws?

6. What shape is the ant-lion’s head? How does it use this head in taking its prey? In digging its pit?

7. Take a doodle-bug to the schoolroom, place it in a dish of sand, covered with glass, and watch it build its pit.

8. Read in the entomological books about the cocoon of the ant-lion and what the adult looks like, and then write an ant-lion autobiography.

_Supplementary reading_--Insect Stories, Kellogg, “The True Story of Morrowbie Jukes.”

THE MOTHER LACE-WING AND THE APHIS-LION

_Teacher’s Story_

Flitting leisurely through the air on her green gauze wings, the lace-wing seems like a filmy leaf, broken loose and drifting on the breeze. But there is purpose in her flight, and through some instinct she is enabled to seek out an aphis-ridden plant or tree, to which she comes as a friend in need. As she alights upon a leaf, she is scarcely discernible because of the pale green of her delicate body and wings; however, her great globular eyes that shine like gold attract the attention of the careful observer. But though she is so fairy-like in appearance, if you pick her up, you will be sorry if your sense of smell is keen, for she exhales a most disagreeable odor when disturbed--a habit which probably protects her from birds or other creatures which might otherwise eat her.

However, if we watch her we shall see that she is a canny creature despite her frivolous appearance; her actions are surely peculiar. A drop of sticky fluid issues from the tip of her body, and she presses it down on the surface of the leaf; then lifting up her slender abdomen like a distaff, she spins the drop into a thread a half inch long or more, which the air soon dries; and this silken thread is stiff enough to sustain an oblong egg, as large as the point of a pin, which she lays at the very tip of it. This done she lays another egg in a like manner, and when she is through, the leaf looks as if it were covered with spore cases of a glittering white mold. This done she flies off and disports herself in the sunshine, care free, knowing that she has done all she can for her family.

Comstock’s Manual.]

After a few days the eggs begin to look dark, and then if we examine them with a lens, we may detect that they contain little doubled-up creatures. The first we see of the egg inmate as it hatches, is a pair of jaws thrust through the shell, opening it for a peep-hole; a little later the owner of the jaws, after resting a while with an eye on the world which he is so soon to enter, pushes out his head and legs and drags out a tiny, long body, very callow-looking and clothed in long, soft hairs. At first the little creature crawls about his egg-shell, clinging tightly with all his six claws, as if fearful of such a dizzy height above his green floor; then he squirms around a little and thrusts out a head inquiringly while still hanging on “for dear life.” Finally he gains courage and prospects around until he discovers his egg stalk, and then begins a rope climbing performance, rather difficult for a little chap not more than ten minutes old. He takes a careful hold with his front claws, the two other pairs of legs carefully balancing for a second, and then desperately seizing the stalk with all his clasping claws, and with many new grips and panics, he finally achieves the bottom in safety. As if dazed by his good luck, he stands still for a time, trying to make up his mind what has happened and what to do next; he settles the matter by trotting off to make his first breakfast of aphids; and now we can see that it is a lucky thing for his brothers and sisters, still unhatched, that they are high above his head and out of reach, for he might not be discriminating in the matter of his breakfast food, never having met any of his family before. He is a queer looking little insect, spindle-shaped and with peculiarly long, sickle-shaped jaws projecting from his head. Each of these jaws is made up of two pieces joined lengthwise so as to make a hollow tube, which has an opening at the tip of the jaw, and another one at the base which leads directly to the little lion’s throat. Watch him as he catches an aphid; seizing the stupid little bag of sap in his great pincers, he lifts it high in the air, as if drinking a bumper, and sucks its green blood until it shrivels up, kicking a remonstrating leg to the last. It is my conviction that aphids never realize when they are being eaten; they simply dimly wonder what is happening.

It takes a great many aphids to keep an aphis-lion nourished until he gets his growth; he grows like any other insect by shedding his skeleton skin when it becomes too tight. Finally he doubles up and spins around himself a cocoon of glistening white silk, leaving it fastened to the leaf; when it is finished, it looks like a seed pearl, round and polished. I wish some child would watch an aphis-lion weave its cocoon and tell us how it is done! After a time, a week or two perhaps, a round little hole is cut in the cocoon, and there issues from it a lively little green pupa, with wing pads on its back; but he very soon sheds his pupa skin and issues as a beautiful lace-wing fly with golden eyes and large, filmy, iridescent, pale green wings.

LESSON LXXXIX

THE MOTHER LACE-WING AND THE APHIS-LION

_Leading thought_--The lace-wing fly or golden-eyes, as she is called, is the mother of the aphis-lion. She lays her eggs on the top of stiff, silken stalks. The young aphis-lions when hatched, clamber down upon the leaf and feed upon plant-lice, sucking their blood through their tubular jaws.

_Method_--Through July and until frost, the aphis-lions may be found on almost any plant infested with plant-lice; and the lace-wing’s eggs or egg-shells on the long stalks are also readily found. All these may be brought to the schoolroom. Place the stem of a plant infested with aphids in a jar of water, and the acts of the aphis-lions as well as the habits of the aphids may be observed during recess or at other convenient times, by all the pupils.

_Observations_--1. When you see a leaf with some white mold upon it, examine it with a lens; the mold is likely to be the eggs of the lace-wing. Is the egg as large as a pin head? What is its shape? What is its color? How long is the stalk on which it is placed? Of what material do you think the stalk is made? Why do you suppose the lace-wing mother lays her eggs on the tips of stalks? Are there any of these eggs near each other on the leaf?

2. If the egg is not empty, observe through a lens how the young aphis-lion breaks its egg-shell and climbs down.

3. Watch an aphis-lion among the plant-lice. How does it act? Do the aphids seem afraid? Does the aphis-lion move rapidly? How does it act when eating an aphid?

4. What is the general shape of the aphis-lion? Describe the jaws. Do you think these jaws are used for chewing, or merely as tubes through which the green blood of the aphids is sucked? Do the aphis-lions ever attack each other or other insects? How does the aphis-lion differ in appearance from the ladybird larva?

5. What happens to the aphis-lion after it gets its growth? Describe its cocoon if you can find one.

6. Describe the little lace-wing fly that comes from the cocoon. Why is she called, golden-eyes? Why lace-wing? Does she fly rapidly? Do you suppose that if she should lay her eggs flat on a leaf, that the first aphis-lion that hatched would run about and eat all its little brothers and sisters which were still in their egg-shells? How do the aphis-lions benefit our rose bushes and other cultivated plants?

_Supplementary Reading_--“A Tactful Mother” in Ways of the Six-Footed.

THE MOSQUITO

_Teacher’s Story_

In defiance of the adage, the mother of our most common mosquitoes does not hesitate to put her eggs all in one basket, but perhaps she knows it is about the safest little basket for eggs in this world of uncertainties. If it were possible to begin this lesson with the little boat-shaped egg baskets, I should advise it. They may be found in almost any rain barrel, and the eggs look like a lot of tiny cartridges set side by side, points up, and lashed or glued together, so there shall be no spilling. Like a certain famous soap, they “float,” coming up as dry as varnished corks when water is poured upon them.

The young mosquito, or wriggler, breaks through the shell of the lower end of the egg and passes down into the water, and from the first, it is a most interesting creature to view through a hand lens. The head and the thorax are rather large while the body is tapering and armed with bunches of hairs. At the rear of the body are two tubes very different in shape; one is long, straight and unadorned; this is the breathing tube through which air passes to the tracheæ of the body. This tube has a star-shaped valve at the tip, which can be opened and shut; when it is opened at the surface of the water, it keeps the little creature afloat and meanwhile allows air to pass into the body. When the wriggler is thus hanging at an angle of 45 degrees to the surface of the water, it feeds upon small particles of decaying vegetation; it has a remarkable pair of jaws which are armed with brushes, which in our common species, by moving rapidly, set up currents and bring the food to the mouth. This process can be seen plainly with a lens. When disturbed, the wriggler shuts the valve to its breathing tube, and sinks. However, it is not much heavier than the water; I have often seen one rise for some distance without apparent effort. The other tube at the end of the body, supports the swimming organs, which consist of four finger-like processes and various bunches of hairs. When swimming, the wriggler goes tail first, the swimming organs seeming to take hold of the water and to pull the creature backward, in a series of spasmodic jerks; in fact, the insect seems simply to “throw somersaults,” like an acrobat. I have often observed wrigglers standing on their heads in the bottom of the aquarium, with their jaws bent under, revolving their brushes briskly; but they never remain very long below the surface, as it is necessary for them to take in fresh air often.

Drawn by Evelyn Mitchell.]

The pupa has the head and thoracic segments much enlarged, making it all “head and shoulders” with a quite insignificant body attached. Upon the thorax are two breathing tubes, which look like two ears, and therefore when the pupa rests at the surface of the water, it remains head up so that these tubes may take in the air; at the end of the body are two swimming organs which are little, leaf-like projections. At this stage the insect is getting ready to live its life in the air, and for this reason probably, the pupa rests for long periods at the surface of the water and does not swim about much, unless disturbed. However, it is a very strange habit for a pupa to move about at all. In the case of other flies, butterflies, and moths, the pupa stage is quiet.

When fully mature, the pupa rises to the surface of the water, the skeleton skin breaks open down its back and the mosquito carefully works itself out, until its wings are free and dry, meanwhile resting upon the floating pupa skin. This is indeed a frail bark, and if the slightest breeze ruffles the water, the insect is likely to drown before its wings are hard enough for flight.

The reason that kerosene oil, put upon the surface of the water where mosquitoes breed, kills the insects is because both the larvæ and pupæ of mosquitoes are obliged to rise to the surface, and push their breathing tubes through the surface film so that they will open to the air; a coating of oil on the water prevents this, and they are suffocated. Also when the mosquito emerges from the pupa skin, if it is even touched by the oil, it is unable to fly and soon dies.

The male mosquitoes have bushy, or feathery, antennæ. These antennæ are hearing organs of very remarkable construction; (see Ways of the Six-Footed, p. 8.) The Anopheles may be distinguished from the Culex by the following characteristics: Its wings are spotted instead of plain. When at rest it is perfectly straight, and is likely to have the hind legs in the air. It may also rest at an angle to the surface to which it clings. The Culex is not spotted on the wings and is likely to be humped up when at rest. In our climate the Anopheles is more dangerous than the Culex because it carries the germs of malaria. A mosquito’s wing under a microscope is a most beautiful object, as it is “trimmed” with ornamental scales about the edges and along the veins. The male mosquitoes neither sing nor bite; the song of the female mosquito is supposed to be made by the rapid vibration of the wings, and her musical performances are for the purpose of attracting her mate, as it has been shown that he can hear through his antennæ a range of notes covering the middle and next higher octaves of the piano.

Of late we are learning that the mosquitoes are in a very strange way a menace to health. Through a heroism, as great as ever shown on field of battle, men have imperiled their lives to prove that the germs of the terrible yellow fever were transmitted by the biting mosquito, and with almost equal bravery other men have demonstrated that the germs of malaria are also thus carried.