,0^ s ^ .A to %'^ ^\-^ .^'^' ^ '^SS^^^ ■ '^c^ '^^V .^^' -. "oo jf-.r- .5 ^c. x^' « \ x'^' «>■ 0- \^' ^ ^ * /■ . 0^ > ,0' --r'.^ ^ci-. ,V ' 8 ^ %: v<}^ ^y^ W^JAM^ • - s - , ^/> * '^ ^ « ' X^^ . '^^- s%^- ' <^^ X' s- INJURIOUS INSECTS THE MACMILLAN COMPANY NEW YORK ■ BOSTON • CHICAGO DALLAS • SAN FRANCISCO MACMILLAN & CO., Limited LONDON • BOMBAY • CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Ltd. TORONTO The Colorado Potato-beetle. Forerunner of Modern Methods of Insect Control. Original. See pages 63 and 145. INJURIOUS INSECTS HOW TO EECOGNIZE AND CONTROL THEM BT WALTER C. O'KANE ;/ ENTOMOLOGIST TO THE NEW HAMPSHIRE EXPERIMENT STATION AND PROFESSOR OF ECONOMIC ENTOMOLOGY IN NEW HAMPSHIRE COLLEGE ILLUSTRATED WITH 600 OBIGINAL PHOTOGRAPHS Neb} gork THE MACMILLAN COMPANY 1912 All rights reserved <0 <^t Copyright, 1912, By the MACMILLAN COMPANY. Set up and electrotyped. Published November, 1912. NorfaootJ iPregg J. S. Gushing Co. — Berwick & Smith Co. Norwood, Mass., U.S.A. €:C(.A32?933 TO HEEBERT OSBORN DEVOTED SCIENTIST • IISrSPIRING TEACHER GENUINE FRIEND ACKNOWLEDGMENT The author wishes to acknowledge his obligation to the many friends and co-workers who loaned or gave specimens needed for the preparation of the illustrations in this book. While all of the illustrations are original and are prepared from photographs by the author, it would not have been possible to carry through this part of the work without the help of others. The late Dr. J. B. Smith gave freely many excellent specimens from his collections. A great deal of valuable material was furnished by Dr. E. P. Felt. Special acknowledgment is due also to Dr. L. 0. Howard and his associates, Mr. A. L. Quaintance, Dr. F. H. Chitten- den, Mr. W. D. Hunter, Mr. F. M. Webster, Mr. E. A. Schwarz, Dr. A. D. Hopkins, Dr. H. G. Dyar, Mr. So A. Rohwer, and Mr. Otto Heidemann. Similar generous courtesies were extended by Dr. W. E. Britton, Mr. P. J. Parrott, Professor G. W. Herrick, Dr. S. A. Forbes, Pro- fessor H. A. Gossard, Professor H. Osborn, Professor C. P. Gillette, Dr. T. J. Headlee, Professor F. L. Washburn, Professor Wilmon Newell, Professor R. H. Pettit, Dr. E. D. Ball, Mr. E. L. Worsham, Dr. H. T. Fernald, Prof. Franklin Sherman, Jr., Dr. W. E. Hinds, Professor H. Garman, Mr. Lawson Caesar, Professor T. B. Symons, Mr. N. E. Shaw, Dr. E. G. Titus, Dr. Leonard Haseman, Dr. Edith M. Patch, Prof. R. L. Webster, Mr. J. S. Houser, Prof. A. G. Ruggles, Mr. C. R. Crosby, Mr. F. E. Brooks, Mr. Patricio Cardin, Mr. J. J. Davis, Dr. H. J. Franklin, and Mr. W. S. Abbott. Grateful acknowledgment is here made to the author's assistants. Miss Cornelia F. Kephart and Mr. C. H. Hadley, Jr., for their invalu- able and skillful help throughout the work of preparing both illustra- tions and manuscript. ARRANGEMENT OF INJURIOUS SPECIES IN THIS BOOK The insect pests described in this book are grouped as follows : 1. Pests of garden and field crops; including all injurious species commonly found on such plants as corn, potatoes, cucumbers, wheat, squashes, and the like. With these are included pests of greenhouses. 2. Pests of orchard and small fruits: the common injurious species of apples and other tree fruits, currants and similar bush fruits, and strawberries or other low-growing plants, usually designated as fruits. 3. Pests of the household, of stored products, and of domestic ani- mals. These comprise the common injurious species that do not feed on living plants. Within each of the first two groups the various species are arranged according to the place where they are found at work. Thus, insects that work within the soil are treated first; then the borers found within stem, trunk, or imb; then the pests found feeding on the surface of stem or trunk; then the leaf feeders; and finally the insects attacking flower or fruit. Among leaf feeders, again, the insects are grouped according to their general characteristics, whether caterpillars, sucking bugs, and so on. The page headings are arranged to serve as an index to the place where an insect is found at work, and its general characteristics. The author hopes by this means to facilitate the identification of a pest by those who are not familiar with insects, and to avoid as far as possible the duplication inevitable where one attempts to group pests according to host plants — a confusion unavoidable because so many of our common pests feed on several varieties of plants, and may properly be listed as well under one as under another. IX CONTENTS I. II. III. w. V. VI. VII. VIII. IX. X. XI. XII. XIII. XIV. XV. XVI. XVII. XVIII. XIX. XX. Introduction 3 The Parts of an Insect's Body 7 The Internal Structure of Insects .... 11 The Senses of Insects 16 The Behavior of Insects . . . . . .18 How Insects Transform 19 How Insects are Classified 22 How Insects Spread ... .o.. 40 Insects as Carriers of Disease ..... 42 The Natural Enemies of Insects .... 45 Farm Practice in Relation to Insect Control . 55 Direct Control by Mechanical Means ... 59 Insecticides — General Principles ... 63 Poison Insecticides — For Biting Insects . . 65 Contact Insecticides — For Sucking Insects . . 70 Repellents . . 79 fumigants 80 Fungicides Combined with Poisons .... 85 Spray Machinery — General Principles ... 89 Types and Sizes of Spray Pumps. Dusting Appa- ratus . . . . ' 92 Accessories 100 Insect Pests of Garden and Field Crops . . 107 Insect Pests of Orchard and Small Fruits . . 224 Insect Pests of the Household and Stored Prod- ucts 349 Insect Pests of Domestic Animals .... 371 xi PART I THE STRUCTURE, HABITS, AND CLASSI FICATION OF INSECTS INJURIOUS II^SECTS CHAPTER I Introduction The Tax paid to Insects Insects exact of the human race an enormous toll in property injured and destroyed. Unfortunately, in the interrelations of life, most things that man desires, uses, or needs are the natural food of one or another species of insect, usually of many. Specific examples of insect depredations give one some notion of the total. Thus, in a limited area in southern Indiana and near-by counties, a species of cutworm attacking corn caused a loss in one year, 1908, of $200,000. The tobacco flea beetle in a single season, in Kentucky and Tennessee, infhcted damage to the extent of $2,000,000. Injury by a plant louse, the pea aphis, in two years of abundance, was esti- mated at $7,000,000. In the Black Hills National Forest, a species of beetle has destroyed timber representing at least 1,000,000,000 feet of lumber. The annual price of the boll weevil to cotton growers is figured at $15,000,000 to $30,000,000. Losses due to the cattle tick reach a total of $40,000,000 each season. In a single year of excessive abun- dance the Hessian fly exacted from our farmers an estimated total of $100,000,000. In Ohio the yield of wheat in that one season dropped from 15 bushels per acre to 6. The ravages of the chinch bug in our crops of wheat and corn in the last 60 years are believed to reach the sum of $350,000,000. Yet these examples are but one phase of the matter, representing a few of the notable insect outbreaks that have been studied and esti- 3 4 INTRODUCTION- mated. By far the greater part of the annual toll goes unrecorded, — often unnoticed. Each season every crop on every farm pays its tax, whether large or small, to the busy, six-footed creatures that look to it for food. It is only when we stop to consider what this total must be, reckoned as a percentage of the value of all crops combined, that its tremendous proportions become evident. The best observers agree that, in the average, insect depredations equal at least 10 per cent of the value of all farm crops. Our agricul- tural products in this country have now reached an annual worth of $10,000,000,000. The total damage wrought by insects, therefore, may fairly be placed at $1,000,000,000 each season! This is nearly five times as great as the combined appropriations for the United States army and navy; is equal to the entire bonded debt of the United States ; is more than four times the annual property loss by fire ; more than fourteen times the annual income of all colleges in this country ; is sixty times greater than the funds allotted annually to the United States Department of Agriculture. Value of a Knowledge of Insects Unquestionably, the loss due to insect attack may be reduced ma- terially by the adoption of proper methods of prevention and control. In many cases, the program to adopt involves no direct fighting, such as spraying, but simply the shaping of farm, garden, or orchard practice along lines unfavorable to the insects concerned — such matters as judicious rotation of crops, or cleaning fields of weeds. To-day's warfare against insect pests strives toward prevention as well as cure. In order to plan our campaign intelligently we need to know the more important general facts about insects as a class : the main charac- teristics of the different groups with which we have to deal ; how they have fitted themselves to survive and multiply; what measures of control are adapted to particular groups ; how the structure and habits of one group render it susceptible to certain kinds of control measures, such as spraying, while in other groups wholly different measures are necessary. To know these general facts is to possess a fundamental advantage in conducting -successful warfare. Not to know them usu- CHARACTERISTICS OF INSECTS ' 5 ally means the loss of time and money in attempting unsuitable remedies or neglecting good opportunities. Characteristics of Insects The place of insects in the animal world is in a group known as Arthropoda, a word meaning " jointed foot." They are related on the one hand to spiders, scorpions, and cen- tipedes, and on the other to crabs, crayfish, and the other crustaceans. With these animals they have various points in common ; for example, a hard- ened body wall or " external skeleton," jointed legs occurring always in pairs, and a body made up of distinct rings or segments. Other characteristics are peculiar to insects alone, and serve to define them. These are as follows : a body composed of three distinct regions, head, thorax, and abdomen; one pair of compound eyes; one pair of antennse, or "feelers"; three pairs of legs; two pairs of wings ; and a peculiar, complicated tyj^e of growth, called metam.orphosis, by which the individual goes through three or four unlike stages in its life round. Fig. 1. — A mite. An ar- thropod, related to insects. Enlarged and natural size. Original. Fig. 2. — A typical insect, showing the parts of the body and the attachment of appendages. Original. Fig. 3. — Types of antennae, a. pectinate; b, moniliform ; c, filiform; d, lamellate; e, capitate; /, geniculate; g, cla- vate ; h, serrate. Original. 6 CHAPTER II The Parts of an Insect's Body The Head Adult insects have a more or less distinct head, varying greatly in shape according to the habits of the species. Prominent on either side, near the top of tlie head, are usually to be seen the compound eyes. These are very large in some groups, such as the horseflies or dragon flies, which need to have espe- cially good vision, but are absent in some other groups, such as certain parasites, which have little need of the ability to see. A com- pound eye is made up of many lenses, each with its own sensi- tive area and nerve. The num- ber of these lenses often is great ; the common house fly has about 4000 on each side. Between or above the compound eyes are usually three simple eyes, out readily by looking closely. Near the compound eyes are the antennae, or " feelers." Their shape is diverse with the different groups, and is one of the valuable means of determining the identity of many insects, or of placing a specimen in its proper group. Eight or ten general types of antennae are recognized. 7 Fig. 4. — Head of a beetle, showing mouth parts. Enlarged and natural size. Original. These are small, but can be made 8 THE PARTS OF AN INSECT'S BODY The remaining prominent structures on the head of an insect are the mouth parts. From a practical standpoint, there is no other one thing in the makeup of an insect's body so important as the type of mouth parts in a given pest. All insects may be divided into two classes, according to whether they obtain their food by biting and chewing, or by sucking ; in other words, whether they have biting or sucking mouth parts. Fig. 5. — Mouth parts of a beetle. a, labrum; b, mandibles; c, maxillae; d, labium; e, hypopharynx. Original. If we examine the head of a beetle, for instance, we shall find that it possesses a distinct pair of jaws, or mandibles, obviously intended for chewing or biting. Above these is an upper Up, or labrum ; below is a pair of maxillae, serving to hold the food and otherwise to assist in eating ; and below these a lower lip or labium. If we look closely, we shall be able to find between the mouth parts the insect's tongue, or hypopharynx. HEAD AND THORAX 9 But if we observe the head of a squash bug, we find no jaws or other parts that would serve to chew or bite. Instead there is a stout beak, . and if we were to dissect this, w^e should find that it contained a tube for sucking up plant juices or other fluids. In ad- dition, we should find in most insects of this type, two or three pairs of lancets within or close to the beak, used to puncture or rasp the tissues so as to induce a greater flow of the juices. Insects with l)iting mouth parts may be killed by cov- ering the plant on which they feed with a poison, such as lead arsenate. But insects with sucking mouth parts do not eat the surface of the plant and cannot be killed by applica- tions of stomach poison. For the latter other remedies must be used, such as some substance that will kill the insect by corrosive action on its body. The Thorax The middle part of an insect's body is called the thorax. Usually it has three distinct rings, or segments. On each segment is a pair of legs and on each of the last two is a pair of wings, except in the group of two-winged flies, which have only a single pair, on the middle segment. An insect's leg consists, typically, of a small joint next the body, the trochanter; a large and heavy joint, the femur; a slender tibia; Fig. 6. — Mouth parts of a honeybee. Enlarged. Original. Fig. 7. — Mouth parts of a horsefly, fitted for pierc- ing and sucking. Enlarged. Original. 10 THE PARTS OF AN INSECT^ S BODY Fig. 8. — Foot of an in- sect, showing claws and pulvillus. Enlarged. Original. and a foot, or tarsus, made up of five joints, or sometimes less. On the end of the tarsus often occur claws between which is a small pad, or pulvillus. The wings vary greatly in size, shape, and texture. They constitute an important char- acter in separating insects into various groups, as will be seen. For example, beetles are easily recognized by the possession of a front pair of wings that are hardened or horny and serve simply as covers for the large, membranous hind wings. The Abdomen The third, or hind part of an insect's body is called the abdomen. It consists often of ten rings or segments, though frequently this number is reduced. There are never any legs on the abdomen of the adult insect. At the hind extremity in both sexes are the reproduc- tive organs. The two sexes are invariably separate in insects, and never normally combined in a single individual as in some other forms of lower animal life. CHAPTER III The Internal Structure of Insects How Insects Breathe All insects, even those hving in water, need air. But their method of obtaining it is entirely different from that developed in higher animals. No insect has nostrils, or any opening in its head through which it breathes. Instead, there is a row of small apertures, called spiracles, down each side of its body, one on each segment, beginning with the second or third segment of the thorax and extending back along the rings of the abdomen. The spiracles of each side open into an air tube running lengthwise of the insect, just within the body wall. From these main tubes smaller tubes diverge, and these in turn branch and re- branch, growing constantly smaller, until the finer tubes permeate every part of the insect, even to the tips of the antennae and the joints of the feet. The tubes are known as trachese and the entire group as the tracheal system. The smaller 11 Fig. 9. — Tracheal system of an insect, gramniatic) Original. (Dia- 12 THE INTERNAL STRUCTURE OF INSECTS Fig. 10. — Spiracles of a grasshopper. Enlarged. Original. higher animals, whose blood circulates in ar- teries, veins, and capil- laries. In insects the blood flows freely around the internal organs and through the tissues. There is a heart, how- ever, which keeps the blood moving. It is an elongated structure, situ- ated just beneath the upper surface of the in- sect's body, and consists of a series of chambers, each with valves opening from the body cavity into the chamber, and with another valve open- ing into the next chamber toward the front. The tracheae are extremely thin walled, and the oxygen that they contain is thus brought to the various tissues. Air circulates slowly in the tracheae. The openings or spiracles are guarded by various devices, such as a fringe of hairs. The Circulatory System The entire body cavity of an insect is bathed in a yellowish or greenish fluid that we speak of as its blood. There is no closed system of blood vessels, as in the Fig. 11. An insect's heart. Original. (Diagrammatic.) THE DIGESTIVE SYSTEM 13 end of the heart toward the head opens into the body cavity. When the heart contracts, the blood it contains is forced forward, and when it expands, more blood is admitted through the side valves. The Digestive System There is a fairly close parallel between the digestive system of in- sects and that of some higher animals. The various organs concerned Fig. 12. — Digestive system of an insect. (Diagrammatic.) Original. are much m.odified in many species, according to their food habits; but taking a typical group, we find the following parts : From the mouth the food passes through a pharynx and is con- veyed by a gullet or esophagus to a crop, which serves as a storage place. Thence it enters the gizzard, where it is ground up, and so passes on into the storaach, where part of the digestion and absorp- 14 THE INTERNAL STRUCTURE OF INSECTS tion takes place. Thence it enters the intestine, where it is still further digested. The waste is expelled from the hind end of the body. Opening into the intestine near the stomach are tubes that prob- ably serve as kidneys. They are known as Malpighian tubes. The Nervous System Most insects are extremely active creatures, and have a well-de- veloped nervous system. Taking a simple type, we find that a pair of nerve cords begin in the upper part of the head, encircle the esophagus, one on each side, again come close together or unite, and extend back to the hind ex- tremity of the body, lying just above the lower body wall throughout. In the upper part of the head and in the lower part are enlargements, called ganglia, from which are given off branch nerves to the eyes, antennae, and mouth parts. In the thorax there are three more ganglia, one for each segment, though these may be more or less united. In the abdomen are further ganglia, often somewhat concen- trated toward the front end of the abdomen. Many branch nerves arise from the thoracic and abdominal gangha. Fig. 13. — Gizzard of a cricket, showing muscles and grinding surfaces. Enlarged. Original. The Fat Bodies Within the body cavity are many irregular masses of peculiar fatty tissue. The functions of these masses are not fully understood. It is known, however,, that reserve food is stored up in them, especially THE BODY WALLS 15 in the case of caterpillars that are reaching full growth and getting ready to transform. Fig. 14. — Nervous system of an insect. (Diagrammatic.) Original. The Body Walls The bodies of most insects are covered with a more or less horny or hard coating, to which the muscles are attached, and which takes the place of the bony, internal skeleton of higher animals. The basis of this coating is a fluid substance called chitin, which hardens on exposure to air. In order to permit of movement, this outer shell is made up of distinct plates, joined to one another by flexible skin. CHAPTER IV The Senses of Insects It is obvious that most insects possess a well-developed power of sight. It is not believed that they have the ability to form images of objects, in other words to " see," with the precision of higher ani- mals. To a limited extent the compound eyes probably give an insect certain powers of forming images up to a short distance — not more than a few feet. They undoubtedly are well adapted to discern movement. The ocelli, or simple eyes, are formed somewhat on the plan of the human eye ; but the lens is of fixed focus, and the number of nerves in the retina is comparatively small. The sense of hearing is well known to exist among many insects. The location of the auditory apparatus has been de- termined in certain species. Thus, the antennae of some insects are known to have auditory functions; grasshoppers have an " ear " on the first segment of the abdomen; other species have a similar organ on the foreleg. Most insects have a sense of taste. The hypopharynx, or tongue, and short appendages attached to the maxillae, or lower jaws, are commonly the seat of this sense. There is abundant evidence of the existence of a sense of smell. In fact this sense is particularly well developed in many insects, and serves to guide them to their food, to lead the females to the proper plants on which to deposit their eggs, and often to bring the male to 16 Fig. 15. — Tongue of a cricket. Enlarged and natural size Original. SPECIAL SENSE ORGANS 17 the female at mating season. Minute structures found in the antennae and the maxillary palpi are commonly the seat of the olfactory sense. All insects have more or less specially developed parts for exercising the sense of touch. The antennae, or " feelers," are primarily adapted to serve this function, but hairs or bristles connected with sensory nerves occur at various places over the body. This would be expected, since the body is so completely covered with its armor of chitin. CHAPTER V The Behavior of Insects Most of the movements of insects are automatic responses to a direct external stimulus. For example, ants of certain species always move away from the hght ; flies, toward it. Roaches will attempt to crowd into narrow crevices, where their body is in close contact all around with the surrounding substance. Some kinds of caterpillars habitually crawl toward the ends of twigs, or contrary to gravity. Aquatic insects move toward water. Most of the movements of insects, if carefully analyzed, will be found explainable as some of these simple reactions. But there is another group of movements that are really complex. An example is seen in the spinning of its cocoon by a caterpillar. Here we have genuine evidence of the workings of instinct. Yet even these ex- amples of insect behavior have one point in common ; they are started by some simple stimulus, and once set going, they invariably are carried out to the same conclusion, regardless of circumstances. Thus, a female codling moth, the parent of the common worm found in apples, frequently lays its eggs on the leaves of trees which are bear- ing no fruit, with the inevitable result that all its offspring die. Rarely, in the highly specialized orders, such as the bees or ants, insects are observed to follow a procedure that seems to demand some reasoning power as its basis. An indi\'idual apparently will learn by experience, and voluntarily modify its procedure in going through a similar action. Such cases, however, are not common. Most insect behavior is automatic and purely reflex. 18 CHAPTER VI How Insects Transform All insects, except two primitive groups of little importance, go through distinct changes of form in the life round of the individual. These changes constitute what is known as metamorphosis. Fig. 16. — Iliustratinp; complete metamorphosis. Egg, larva or caterpillar, cocoon and pupa, and adult of the Rusty Tussock Moth, Hcmerocampa an- tiqua Linn. Original. Thus, the cabbage butterfly lays an egg. From the egg hatches a tiny ■' worm " or larva. The larva grows, and in due time changes 19 20 HOW INSECTS TRANSFORM to a '' clirysalis " or pupa. And finally, from the pupa emerges the winged butterfly, ready to begin the life round over again. This is an example of complete metamorphosis, including four distinct stages — egg, larva, pupa, and adult. With the squash bug we find the adult laying an egg, as before. But from this egg hatches, not a larva or worm, but a tiny, active bug, Fig. 17. — Illustrating incomplete metamorphosis. Eggs, nymphs of the Squash Bug, Anasa tristis De G. Original. and adult similar to the parent insect except that it has no wings. This immature form grows, shedding its skin four or five times, and finally with the last moult acquires its wings and is now a typical adult. The imma- ture stage is known as a nymph, and this is an example of incomplete metamorphosis, including only three distinct stages instead of four — egg, nymph, and adult. In all insects the larval or nymph stage is the period of growth. TYPES OF METAMORPHOSIS 21 To this stage belongs primarily the function of feeding and growing. The adult insect may or may not feed, but it never grows. To the adult stage belongs the function of mating and thus perpetuating the race. The pupa, which we find in insects with complete metamor- phosis, represents a resting stage devised to accommodate the tre- mendous changes taking place in the transformation of the wormlike larva into the winged adult. The type of metamorphosis constitutes a fundamental character in separating insects into groups. CHAPTER VII How Insects are Classified More than 350,000 distinct species of insects have been described. In addition at least as many more remain to be studied and classified. Obviously, in all this array, there must be certain groups that have many characters in common, or give indication that at some period in the remote past they were derived from common ancestors. These groups are known as Orders. There are more than twenty recog- nized orders of in- sects, but the great majority of injurious species are included in ten principal eco- nomic orders. The leading characteris- tics distinguishing these from one an- other are the type of metamorphosis, the kind of mouth parts, the number, shape, and texture of the wings, the presence or absence of compound eyes, the type of antennae, and the shape of the body. The ten principal orders and their characteristics are as follows: Fig. 18. — A typical specimen of the order Orthop- tera. Original. ORTHOPTERA 23 Orthoptera Familiar to all are many of the species that go to make up this order: the grasshoppers, katydids, crickets, and roaches. The entire group is characterized by incomplete metamorphosis. The immature form just hatched from an egg is quite similar in appear- ance to the adult, except that it is very much smaller, and that it has no wings. As it grows, wing pads develop, and finally, with the last moult, the adult comes forth. All insects in this order have biting mouth parts. There are two pairs of wings. The front pair are leathery, and, when at rest, cover the hind pair, which are thin and papery, and are folded in plaits. The antennae vary, but frequently are quite long and slender. The order is divided into various subgroups or fami- lies. Thus we have the jumping Orthoptera, includ- ing the Gryllidae or crickets, the Acrididae or grasshop- pers, and the Locustidse or katydids; the running Or- thoptera, including the Blat- tidae or roaches; the grasping Orthoptera, including the Mantidse or praying mantids; and the walking Orthoptera, including the peculiar insects known as the Phasmidse or walking sticks. There are many injurious pests in this order; some of them, such as the Rocky Mountain locust, famous for the devastation that they have wrought to American farms. The immature stages, or nymphs, as well as the adiTlts, are destructive, though in less degree because they are smaller. Fig. 19. -One of the jumping Orthoptera, or GryUidse. Original. 24 HOW INSECTS ARE CLASSIFIED Mallophaga These are parasitic insects, commonly known as bird lice, although there are some species that infest domestic animals. The metamorphosis is incomplete. Eggs laid by the adult female hatch into minute creatures looking much like the mature insect. The members of this order are plainly adapted for their parasitic life. The body is flattened. There are no compound eyes. Wings are absent. The antennae are short and simple. The mouth parts are fitted for biting, and the food consists of the hairs or feathers of the host, or loose scales of dead skin. The Mallophaga never feed on the blood of their host, as do the members of the order Siphonaptera, the fleas. Fig. 20. — A biting louse. En- ., onnn • -u u j larged and natural size. Orig- ^^out 2000 species have been de- inal. scribed. Odonata The adults in this order are the dragon flies, often called " snake feeders " or " darning needles." Metamorphosis is incomplete. The nymphs, which hatch from the eggs, are aquatic, spending their lives beneath the surface of ponds or streams, where they lead an active existence, capturing and devouring such other forms of animal life as come within their reach. The mouth parts of the nymph are peculiarly adapted to its needs, being pro- vided with a hinged lower lip which can be extended, and which bears hooks on its farther edge. By means of these the nymph is enabled to catch its prey unawares. The adults arc large insects, and have two pairs of strong, narrow, 01) ON ATA — THYSANOPTERA 25 Fig. 21. — Adult drtigon fly. Original. membranous wings. Each wing is marked with a shallow notch about midway along its front margin. Adults as well as nymphs are pre- dacious, living on other insects which they capture. Their mouth parts are of the biting type. They have large compound eyes, — as, indeed, we should expect in insects that live by capturing others. The abdomen is slim, and is never provided with a sting of any sort, as is so often supposed. Insects of this order are of importance be- cause they make a business of capturing in- dividuals of other species, many of which we may reasonably assume would be injurious. The order has been carefully studied, and about 2000 species have been described. Thysanoptera Fig. 22. — The empty . pupal skin of a dragon I he group to which has been given this ^^ Original. name is made up of very small insects, many of which the layman will recognize rather by their characteristic work than by acquaintance with the appearance of the insect itself. Their common name is " Thrips." 26 HOW INSECTS ARE CLASSIFIED Fig. 23. — Adult Euthrips tritici Original. thrips, Fitch. Metamorphosis is incomplete. Both nymphs and adults are slender insects, pro- vided with sucking mouth parts. The adults have two pairs of peculiar wings, very nar- row, almost without veins, and fringed along the margins with a row of long hairs, set close together. The wings are laid along the back when not in use. In most species the adults are not more than one tenth or one twelfth of an inch in length. The an- tennae are comparatively short and simple. Usually the presence of these insects is recognized first by a whitening of the leaves or a shriveling of other parts on which they happen to be feeding. Close examination will then reveal the tiny active insect itself. Hemiptera A large group, including the true " bugs," characterized throughout bj^ sucking mouth parts. Metamorphosis is incomplete. Active nymphs, which look more or less like the adults except that they have no wings, hatch from the eggs laid by the parent female. There are two large subdivisions in this order, the Homoptera and the Het- eroptera, distinguished from each other by the type of wings, and the manner in which the beak is attached to the head. In the Homoptera the wings, four Fig. 24. — A cicada. Sub- order Homoptera. Original. in number, are membranous throughout, and when the insect is at rest, usually are held in a slop- HEMIPTERA 27 ing position along the back, like the two sides of a hip roof. The common " locust," or cicada, is a familiar example of this suborder. In the Homoptera the sucking beak arises from the hind part of the lower side of the head. The Heteroptera are well illustrated in the '" squash bug." In this suborder the front pair of wings are horny in the half nearest the in- sect's body, and thinner in the outer half. The hind wings are mem- branous throughout. When at rest, the front wings are laid along the Fig. 25. — The giant water bug, Lethocerus americanus Leidy. Suborder Heteroptera. Original. back, with the thin, outer halves crossed, one on top of the other, while the hind wings are concealed beneath the front pair. Often, when the insect is at rest, its wings look as if they were a part of its body, though there is always the tell-tale diagonal line where the thickened part of the wing gives way to the thinner part. In the Heteroptera the beak arises from the front part of the head, though in many species it is sharply bent so that it points backward beneath the head. The more important families of Homoptera are as follows : Cicadidae, the cicadas or, as commonly called, " locusts." Jassidse, the leaf hoppers. Destructive pests. 28 HOW INSECTS ABE CLASSIFIED PsyllidsD, the psjdlas. Minute, jumping forms. Plant feeders. Aphidida?, the plant lice. Coccidse, the scale insects and mealy bugs. The more important families of Heteroptera are as follows : Reduviidse, the assassin bugs. Predaceous on other insects. Occa- sionally attack man. Have a strong, tliree- jointed beak. Tingitidse, the lace bugs. Wings finely reticulate, looking like lace. Plant feed- ers. Acanthiida^, including some plant feed- ers ; also the common bedbug. Capsidse, the leaf bugs. Usually small. Often injurious. Lygaeida?, the chinch bugs. Destruc- tive plant feeders. Coreidse, the squash bugs. Often ill smelling. Some species rather large. Pentatomidae, the stinkbugs. The family includes both plant feeders and predaceous forms. Thyreocoridse, the negro bugs. Very small forms. Pediculida:', the sucking hce, parasitic on mammals. The number of described species in the Hemiptera exceeds 20,000. Fig. 26. — The giant water bug, wingvS folded. Sub- order Heteroptera. Origi- nal. Coleoptera The order Coleoptera includes the beetles, readily distinguished, as a rule, by the fact that the front pair of wings are hardened and act simply as horny coverings for the larger, membranous hind wings, which are folded beneath the others when at rest. Metamorphosis is complete. There are four distinct stages, instead of three, as with all the other orders mentioned thus far. Eggs are laid by the adults, and from these hatch wormlike larvae, commonly called COLEOPTERA 29 *' grubs." A resting stage, or pupa, follows the completion of growth of the grub. Finally from the i)upa emerges the adult beetle. -A ^'^■. ' "^8!P?^^"^^'^^^H w'vS^^HR''^^^ -'^^^^^Hi i p^ Fig. 27. — A beetle, Lachnosterna. Original. The mouth parts are formed for biting. In one subgroup within this order the head is prolonged in a sort of snout. This is not a sucking organ, but bears at its end true jaws, adapted for biting and chewing. The larvae or " grubs " of the snout beetles have no legs. The antennae are of many dis- tinct types, ranging from simple filiform or moniliform shapes to complex types that can only be classed as " irregular." Some of the subgroups are commonly des- ignated according to the kind of antenna; as, for example, the Clavicorns, the Serricorns. Fig — A nout beetle, Rhynchites, Enlarged and natural size. Original. Lamellicorns, or the Something like 20,000 species have been described. 30 HOW INSECTS ARE CLASSIFIED Larvae and adults feed on decaying Both larvae and adults predaceous. There are many famiUes, in practically all of which are to be found species of importance. A few of the typical families are the following : Carabidae, the ground beetles. Active insects both as larvae and as adults, and usually predaceous. Silphidae, the carrion beetles, animal matter. Coccinellidae, the lady beetles. One of the most beneficial famihes. Elateridae, the click beetles. Parents of the wireworms. Buprestidae, the adults of the " flat-headed borers." Scarabaeidae. Large beetles, well illustrated in the " June bug." The larvae of some feed on decaying animal or vegetable matter, while others are highly injurious. Cerambycidae, the parents of the " round-headed borers." Chrysomelidae. Typical leaf eaters. Examples are the potato beetle, asparagus beetle, and many others. Meloidae, the bhster beetles. Curculionidae, the curcuhos. Snout beetles. The larvae legless grubs. Siphonaptera The Siphonaptera in- clude the fleas. The order is a small one, but is in- teresting because of the adaptations that it exhibits for parasitic or predaceous existence. Metamorphosis is com- plete. From the egg hatches a legless larva, slen- der and wormlike, which later transforms to a pupa, and from this in turn emerges the adult, ready to begin the life round again. Fig. 29. — Adult flea. Enlarged. Original. SIPHONAPTERA AND DIPTERA 31 The adults are practically wingless, though small, scalelike projec- tions from the top of the thorax show where the wings should be, and perhaps once were. The body is flattened laterally, thus enabhng the insect to shp around easily among the hairs of its host. While the sur- face of the body is quite smooth and hard, it is provided with regular rows of stiff bristles, pointing backward, which help to force the insect in the direction in which it wishes to go, and likewise help it to escape from the fingers of its captor. A further evidence of its parasitic life is seen in the entire absence of compound eyes. The mouth parts are fitted for sucking. Diptera The insects falling within this order are easily recognized from the fact that they have only a single pair of membranous wings. The order includes the groups that we speak of as flies, mosquitoes, midges, and gnats. Metamorphosis is complete. The larva is commonly called a maggot, and is without feet. In most species it has no distinct head. In many sub- groups within this order the pupa or resting stage preceding the adult is peculiar in that it is inclosed within the hardened and shortened skin of the larva. The single pair of wings borne by the adult are on the middle segment of the thorax. On the hind segment are a pair of small knobs, 'represent- ing the second pair of wings found in other insects. The mouth parts are primarily of the sucking type, but often are complex, and frequently are modified so that certain of the parts are fitted for piercing or for rasping. Thus, in the horseflies there are sharp lancets in addition to the sucking tube, the former penetrating J ^^^A \ j p r f n /h* Wpp^M y^ (" W Fig. 30. — Adult fly, Tabanus. Enlarged to twice natural size. Original. 32 HOW INSECTS ARE CLASSIFIED the tissues and assistinp; in bringing on a generous flow of blood, which the latter conveys to the insect's pharynx. In the female mosquito similar structures are found, sharp stylets penetrating the flesh and the pharynx pumping the blood up through a sucking tube. The antennae are of various shapes, from the elaborately feathered structures of the male mosquito to the short, peculiar form, orna- mented with a prominent bristle, found in man}^ of the so-called ''flies." Classification within the order is complex, and is based partly on the manner in which the pupal skin is ruptured when the adult emerges, partly on the tj^pe of antenna, partly on the arrangement of the veins in the wings, as well as other structural pecul- iarities. More than 40,000 species have been described. The number of families is verj^ large, but among the more important groups may be mentioned the following : Culicidae, the mosqui- toes. A nuisance to man and domestic animals, and in some cases carriers of disease. Larva? aquatic, as a rule. Chironomidse, the midges (l3ut not the so-called midges attacking wheat, clover, and the like). Larvae often aquatic. Cecidomyiidse, the gall midges. Many injurious species, some of prime importance, as the Hessian fly. Simulidae, the black flies. Attack man and domestic animals. Tabanidae, the horseflies. Asilidae, the robber flies. Predaceous on other insects. Fig. 31. — Adult mosquito. Enlarged and natural size. Original. LEPIDOPTERA 33 Syrphidse, the syrphus flies. The larvae of some species are pre- daceous on noxious insects. (Estridse, the botflies. The larva? are notorious parasites in mam- mals. Muscidse, a very large family including the common house fly. Tachinidse, the tachina flies. The larvse often beneficial because attacking noxious insects. Anthomyiida?, including the root maggots. A special interest attaches to this order because several of its mem- bers have been directly connected with the transmission of serious human diseases, as discussed in a later chapter. Lepidoptera The insects included within this order are the moths, the skippers, and the butterflies. The main characteristic of the order is the fact that the wings and body are covered with minute scales, which are arranged in definite patterns and often give to the wings beautiful and elaborate colors. In all Lepidoptera there is com- plete metamorphosis. The larva is commonly known as a cater- pillar, or simply as a " worm," the latter term more frequently attached to larvae that are not covered with hairs. Thus, on the one hand, we speak of the cabbage worm and the canker worm, on the other the tent caterpillar and the yellow-necked caterpillar. The larvae have three pairs of legs near the front end of the body, a single pair of legs or claspers at the hind end, and usually two to four pairs of fleshy prolegs between. All adults in the order Lepidoptera have four wings, except in cer- tain species where the wings are entirely lacking. The mouth parts Fig. 32. — Scales from the wing of a butterfly, Pontia. Enlarged. Orig- inal. 34 HOW INSECTS ARE CLASSIFIED Fig. 33. — K hutier^y, Argynnis. Original. are fitted for sucking. The adults in this group take only liquid nourishment, or frequently none at all. The larvae, however, are provided with well- developed jaws, adapted for biting and chewing. It is in the larval stage that the represent- atives of this order are injurious. The moth itself, or but- terfly, is harmful only in the sense that it is the parent of a succeeding de- structive stage. The antennae are of three general types, and separate the order into its sub- groups. Butterflies have slender antennae composed of a large number of indistinct rings or segments, with an enlargement or club at the end. In the skippers the club at the end of the antenna is somewhat elongated, and is turned back at the farther end in a slender hook. The antennae of moths are more or less feathered, often elabo- rately so. Butterflies are usu- afly on the wing in the day- light hours, while moths have a tendency to fly at night. Butterflies habitually rest with their wings folded together ver- tically above the body; skip- pers may hold the wings in a similar position, or may hold the front wings vertical and ^^^' 34. -A skipper, A^r^^one. Original. the hind wings horizontal; moths habitually rest with their wings held horizontal or roof like, or curved around the abdomen. The LEPIDOPTERA 35 bodies of butterflies are slender ; those of skippers are rather stout ; the bodies of moths are typically heavy. About 60,000 species are known. In classification among this tremendous number use is made of the markings on the wings, but especially of the veins in the wings. The number of families is very large, and injurious species are found in a large proportion of them. Examples are as follows, though this list necessarily is brief and by no means representative of the entire order : \ ♦ '**' "*%. ..««*- -^i ^\ ^~T",.^. ^H| i^fl HBh^|2^^s