An Elementary Study of Insects Part 1

An Elementary Study of Insects.

by Leonard Haseman.

INTRODUCTION

In the preparation of a book of this nature, to be used in the grade schools, we realize that the one fundamental thing to keep in mind is the economic importance of the insect, be it good or bad. The child wants to know what is good and what is bad and how he can make use of the good and how he can get rid of the bad. And yet there is something more a.s.sociated with the life, work and development of each tiny insect.

There is a story--a story of growth, not unlike that of the developing child, a story of courage, strife and ultimate success or failure, which is as interesting and of greater value to the child than many of the stories of adventure and of historical facts. s.n.a.t.c.hes of these stories will appear in the following chapters along with the studies on insects and their economic importance.

In the development of our grade school system, especially in the rural districts, there is a growing demand for some practical work along with the regular cultural studies. To the child in the rural schools, practical knowledge naturally tends toward agriculture. Many of these boys and girls do not have a chance to pursue studies beyond the grades and it therefore becomes necessary to introduce some elementary agriculture into the grades to supply the natural craving of this vast a.s.semblage of children in the rural schools of our land.

In the search for a study which will give unlimited scope for independent thought and observation and which will lead the child to understand better the forces of nature that affect agriculture, nothing is so readily available and attractive to the child as nature study, an elementary study of the natural sciences. In fact agriculture is primarily a course in nature study where we study how plants and animals struggle for existence.

There is a period in the life of every child when he is especially susceptible to the "call of the fields;" when he roams through woods or by shady brooks gathering flowers, fishing for mud-cats and cleaning out b.u.mble-bees' nests. It is often compared with the life of the savage and is merely the outward expression of an inward craving for a closer relation with nature and her creatures. If one can reach a child while at that age he has a ready listener and an apt pupil. That is the time to guide and instruct the child along the line of nature study.

The most important questions confronting the average teacher in the grade schools are: "What material shall I use and how shall I proceed to direct the child along this line?" First of all use that material which is most readily available, which is most familiar to the child and which will attract and hold his attention. There is nothing so readily available and so generally interesting to both boys and girls as are the thousands of fluttering, buzzing, hopping and creeping forms of insects.

They are present everywhere, in all seasons and are known to every child of the city or farm. They are easily observed in the field and can be kept in confinement for study. Many of them are of the greatest importance to man; a study of them becomes of special value.

In pursuing a study of nature and her creatures one should go into the woods and fields as much as possible and study them where they are found. In this way one can determine how they live together, what they feed on and the various other questions which the inquisitive mind of a healthy child will ask. When field work is not possible, gather the insects and keep them alive in jars where they can be fed and observed.

Some forms cannot be kept in confinement and in such cases samples should be killed and pinned, thereby forming a collection for study.

Most of the forms which are included in the following chapters can be kept in confinement in gla.s.s jars or studies out doors. The studies have been made so general that in case the particular form mentioned is not available any closely related form can be used. Each child should make a small collection of living and pinned insects for study and should be encouraged to observe insects and their work in the field. The collections and many of the observations could be made to good advantage during the summer vacation when the insects are most abundant and active.

Pupils should not be encouraged merely to make observations, but they should be required to record them as well. Brief descriptions of the appearance and development of insects, the injury they do, and remedies for the same, will help fix in mind facts which otherwise might soon be forgotten. Drawings, whenever possible, should also be required. The pupil who can record observations accurately with drawings will not soon forget them. The teacher should therefore require each pupil to provide himself with a note-book for keeping brief, but accurate notes and careful drawings. The drawings should be made with a hard lead pencil on un-ruled paper, the size of the note-book, and the pupils should be encouraged to be neat and accurate.

The author wishes to take this opportunity of expressing his deep appreciation for the many helpful suggestions and other a.s.sistance which Mr. R. H. Emberson, superintendent of Boys and Girls Club Work in Missouri, has given. It was his life-long devotion to the boys and girls of the grade schools and his keen appreciation of their needs that lead him first to suggest to the author the importance of preparing this little book for their use.

LEONARD HASEMAN University of Missouri.

"_The study of entomology is one of the most fascinating of pursuits. It takes its votaries into the treasure-houses of Nature, and explains some of the wonderful series of links which form the great chain of creation. It lays open before us another world, of which we have been hitherto unconscious, and shows us that the tiniest insect, so small perhaps that the unaided eye can scarcely see it, has its work to do in the world, and does it._"

--REV. J. G. WOOD.

CHAPTER I

INSECTS

"_There is a difference between a grub and a b.u.t.terfly; yet your b.u.t.terfly was a grub._"

--SHAKESPEARE.

In undertaking a study of insects it is well first of all to know something about what they are, their general nature, appearance, habits and development. The insects comprise the largest group of animals on the globe. There are about four times as many different kinds of insects as all other kinds of animals combined. Insects vary greatly in size.

Some are as large as small birds, while others are so small that a thousand placed in one pile would not equal the size of a pea.

Insects are commonly spoken of as "bugs." This term, however, is properly used only when referring to the one order of insects which includes the sap and blood-sucking insects such as the chinch bug, bed-bug, squash bug, and the like. Then too, there are many so-called "bugs" which are not insects at all. Spiders, thousand-legs, crawfishes and even earth-worms are often spoken of as bugs.

_What They Are_

[Ill.u.s.tration: Side view of gra.s.shopper with wings and legs partly removed. Note the division of the body into head, thorax, composed of prothorax, mesothorax and metathorax, and abdomen consisting of ring-like segments.]

Insects are variously formed, but as a rule the mature ones have three and only three pairs of legs, one pair of feelers, one pair of large eyes, and one or two pairs of wings. The body is divided into a head, thorax and abdomen. The head bears the eyes, feelers and mouth, the thorax bears the legs and wings, and the abdomen is made up of a number of segments. The presence of wings at once decides whether or not it is an insect, for, aside from bats and birds, insects alone have true wings. These are the distinguishing characters of the full grown insect, but, like birds, they hatch from eggs and while young do not always look like their parents. When young they may take on various shapes as caterpillars, borers, maggots, grubs, hoppers, and the like. Young insects are often difficult to distinguish from true worms, centipedes, snails, and such forms, but after one has collected and reared some of the young and watched them pa.s.s through the different stages and emerge with wings they are much more easily recognized.

_Their Princ.i.p.al Characteristics_

[Ill.u.s.tration: Face of gra.s.shopper enlarged showing parts; ant., antenna; eye, compound eye; oc., ocellus or simple eye; cl., clypeus; lbr., labrum or upper lip; mx. p., maxillary palpus; lb. p., l.a.b.i.al palpus; lab., labium or lower lip.]

Young insects as a rule are soft like caterpillars and maggots, while the old ones usually have a hard body wall, similar to the beetles and wasps. The wings are usually thin and transparent though in some cases they are leathery or hard as in case of beetles or covered with scales as in the b.u.t.terflies. The three pairs of legs are jointed and used for running, climbing, jumping, swimming, digging or grasping. The feelers or antennae are usually threadlike, clubbed, or resemble a feather and extend forward or sidewise from the head. The large eyes are compound, being made up of many great small units which, when magnified, resemble honey-comb. In some cases two or three small bead-like eyes may be present besides the two large eyes. The mouth parts of insects may be formed for chewing, as in the gra.s.shopper, or for sucking up liquids, as in the mosquito. The mouth of an insect is built on an entirely different plan from our own. Chewing insects have an upper and lower lip and between these there are two pairs of grinding jaws. These jaws are hinged at the side of the face and when chewing they come together from either side so as to meet in the middle of the mouth. They therefore work sidewise rather than up and down. The mouth parts of the sucking insects are drawn out to form a sucking tube or proboscis as in case of the b.u.t.terfly or mosquito.

[Ill.u.s.tration: Mouth parts of gra.s.shopper shown in relative position; lbr., labrum; md., mandibles; hyp., hypopharynx; max., maxillae; lab., labium.]

[Ill.u.s.tration: Leg of gra.s.shopper showing segmentation. The basal segment c, is the c.o.xa, the next t, the trochanter, the large segment f, the femur, the long slender one ti, the tibia, and the three jointed tarsus ta, with claws at the tip.]

The internal organs of insects are similar to those of other animals.

The digestive tube consists of oesophagus, gizzard, or stomach, and intestines. The nervous system is well developed as shown by the extreme sensitiveness of insects to touch. The brain is comparatively small except in the bees and ants. The circulatory system consists simply of a long tube heart, the blood vessels being absent. In this way the internal organs of the insect are simply bathed in the blood. The system of respiration is most complicated. The air is taken in through pores usually along the side of the body and is then carried through fine tracheal tubes to all parts of the body. You cannot drown an insect by putting its head under water, since it does not breathe through its mouth. The muscular system is similar to that of other animals which have the skeleton on the outside.

[Ill.u.s.tration: The internal organs of the honey bee. Note the strong wing muscles in the thorax. The tube-like heart begins in the head and extends back through the thorax and follows the curve of the abdomen.

Below the heart is the digestive tube consisting of the slender oesophagus which extends back to the expanded honey stomach, in which the bee carries the nectar it collects from flowers, then the curled true stomach, the small intestine and expanded large intestine. Below this is the nervous system consisting of the brain and a chain of connected enlargements or ganglia extending back into the abdomen in the lower part of the body. The respiratory system in part appears just above the honey stomach, and the black circular or oval spots are cross sections of connecting air tubes, which run all through the body. Also note the sting with the poison gland and sack which are pulled out with the sting; also the sucking tube for getting honey from flowers, and the structures on the legs for gathering and carrying pollen; the pollen basket is on the back side of the hind leg.]

_Their Methods of Developing_

In most cases the parent insect deposits small eggs which hatch later into the young insects. In some cases, as with the blow-flies, the maggot may hatch from the egg while yet in the parent's body, when the active larva is born alive. Whether the egg hatches before or after it is deposited, the young insect continues to develop in one of three ways. It may resemble the parent and simply grow as does a kitten, or it may look somewhat like its parent though smaller and without wings, as the young gra.s.shopper, or it may bear no resemblance whatever to the parent, as the caterpillar which feeds and grows and finally spins a coc.o.o.n in which it pa.s.ses to the resting chrysalis stage and later emerges with wings. The development of insects is therefore extremely complicated.

[Ill.u.s.tration: The chinch bug showing development with incomplete metamorphosis; a, egg; b, first nymph; c, second nymph; d, third nymph; e, fourth nymph; f, adult winged bug; g, chinch bugs extracting sap from corn plant. To control this pest burn over all winter harboring places and use chemical or dust barriers following wheat harvest.]

_The Princ.i.p.al Orders_

In order to study a group of animals which includes so many thousand different kinds it is necessary to divide them into a number of sharply defined divisions or orders. All animal life is naturally grouped into such divisions and subdivisions. Among the insects we at once detect seven large, sharply defined divisions or orders, and ten or more smaller ones. Of these we have first, the two-winged true flies; second, the four-winged b.u.t.terflies and moths; third, the hard-backed beetles; fourth, the stinging four-winged wasps and bees; fifth, the variously formed sucking insects or true bugs, as chinch bugs and bed-bugs; sixth, the rapid-flying four-winged snake doctors or dragon-flies and, seventh, the hopping forms, the gra.s.shoppers. Besides these we have the various smaller orders of water-loving insects, fleas, etc. The seven groups mentioned above include the majority of our common forms and in the studies to follow we will include only representatives from these orders.

[Ill.u.s.tration: The Hessian fly showing development with complete metamorphosis; a, egg; b, larva or maggot; c, flax-seed stage; d, pupa; e, adult winged fly; f, wheat stubble with flax-seed stages near base taken after harvest. To control this pest, plow under stubble after harvest; keep down all volunteer wheat and sow wheat after fly-free date in the fall.]

_Their Habits_

The habits of insects are as varied as their forms and adaptations. Some live in the water all their life, others spend a part of their life under water, others live the care-free life of the open air, others enjoy feeding upon and living in the foulest of filth, others a.s.sociate themselves with certain definite crops or animals thereby doing untold injury, while others produce food and other materials which are to be used by man for his comfort. Every imaginable nook and crook, from the depths of lakes to the tops of mountains, from the warm, sunny south to the cold frigid north, from the foul damp swamps to the heart of our desert lands, offers a home for some small insect.

The most striking habits and developments among insects is found in the more highly advanced families of bees and ants where definite insect societies are formed, resembling in many respects human societies and human activities. Among these villages are established, homes built, battles fought, slaves made, herds kept by shepherds, and even fields cultivated. In these groups we have the nearest approach to human intelligence.