avsvW iNWiNtSJWwN .\t \^\v"^^»sM(MN»«»^9»»sM^\\^^\i!(^^ ^.^W.>^^^^^^^^v^«„«^v«,^,„^^.v-^..,^^^^^^^A^^^v^v^^m^^^v,^^^•<^v.^^^\^^^^v,.^OCv.\\\\^^^^^^^^ Indian Insect Pests. Agents for the Sale of Books rFBLISHED BY The Superintendent of Government Printing, India, Calcutta. In England. E. A. Arnold, 41 & 43, Maddox Street, Boud Street, Loudou, W. Constable & Co., 16, James Street, Haymarket, London, W. Bernard Quaeitch, 15, Piccadilly, W. Deighton, Bell & Co., Cambridge. H. S. King & Co., 65, CornMll, & 9, Pall Mall, London, P. S. King & Son, 2 & 4, Great Smith Street, Westminster, S.W. Grindlay & Co., 54, Parliament Street, London, S.W. Kegan Paul, Trench, Trubner & Co., 43, Gerrard Street, Soho, London, W. B. H. Blackwell, 50 & 51, Broad Street, Oxford. On the Continent. li. FriedlXnder & SoHN, 11, Carlstrasse, i Karl W. Hiersemann, Leipzig. Berlin N.W. i Ernest Leroux, 28, Kue Bonaparte, Paris. Otto Harrassowitz, Leipzig. !' Martinus Nijhoff, The Hague. Rudolf Haupt, Halle, A. S., Germany. In ThAcker, Spink & Co., Calcutta & Simla. Newman & Co., Calcutta. S, K. Lahiri & Co., Calcutta. 11. Cambray & Co., Calcutta. V. Kaltanarama Aiyar & Co., Madras. G. A. Natesan &. Co., Madras. HiGGiNBOTHAM & Co., Madras. Thompson & Co., Madras. S. MURTHY & Co., Madras. Temple & Co., Madras. COMBKIDGE & Co., Madras, A, R. Pjllai & Co., Trivaudrum. India. Thacker & Co., Ld., Bombay. D. B. Taeaporevala, Sons & Co., Bombay. A. J. CoMBRiDGE & Co., Bombay. Radhabai Atmaram Sagoon, Bombay. Sunder Pandubano, Bombay. N. B. Mathur, Superintendent, Nazair Kanun Hind Press, Allahabad. Rai Sahib M. Gulab Singh & Sons, Mufid-i-Am Press, Lahore. Superintendent, American Baptist Mission Press, Rangoon. A, M. & J. Ferguson, Ceylon. Indian Insect Pests. ^A BY H. MAXWELL-LEFROY, M.A., F.E.S., F.Z.5., Imperial Entomologist I I { CALGUTTA : '' ' OFFICE OF THE SUPERINTENDENT ^OjF GON^|flKMMENT PRINTING, INDIA. 1906. Price Re. 1-8 or 2s. St. Albans, 25th Septemhcr iSS^. 'But, meanwhile, I may most truly say that, if the crop or timber or fruit growers of India were furnished with plain and comprehensive accounts of history and habits of the common insect pests, accompanied by wood-cut figures, so as to convey the appearance of pests without wearis ime description of details, all this would be a national benefit, repaying the outlay a hundred times." ELEANOR A. ORMEROD. 348456 ^a y INTRODUCTION. A S Mr. Lefroy lias written this book largely at my instance, -**• I wish to attach a few words in order to explain its scope. It is not a scientific treatise on Entomology, written for the use and training of Entomologists, but is intended to serve the more humble but useful purpose of a manual of ]3ractical information for the use of the intelligent agricul- turist in the protection of his crops from insect pests. It is also hoped that it will be suitable as a text-book for use in Agricultural Schools and Colleges, all of whose students should acquire a working knowledge of insect pests and of the practical measures possible for the protection of crops. With these objects in view, the author has avoided, wherever possible, scientific terminology, using simple English equi- valents which can easily be understood by persons with no scientific training in Entomology. The information available for a l3ook of even this limited scope is very far from complete. A good deal of work has been done in the past for Systematic Entomology in the collection and classification of some groups of Indian insects, more particularly the Butterflies, but it is only within the past few years that any real inquiry has been made into Economic Entomology, dealing with insect pests and their treatment. Eor this reason Mr. Lefroy would prefer to post- pone publication until the material at his disposal is more complete, but I think first, that the information available is already of sufficient importance to give to the public, and second, that the best way of collecting additional information is to interest persons in that already acquired and to show iv INTRODUCTION. clearly the need for further help. Por this purpose the many blanks in this book have designedly been given prominence by the author in the hope that many workers will endeavour to fill them up by careful and intelligent study of insect life. The field for future investigation is unlimited. This book is a testimony to the strenuous efforts made during the past three years in this field by Mr. Lefroy, who is the only Entomologist in the Department of Agriculture. It is hoped that in the near future an entomologist may be employed by each important province for the investigation, prevention and cure of crop pests, but this will not lessen the need for other workers, whose assistance will be warmly welcomed by the Government Entomologist. If this help is freely given, I look forward within a few years to the issue of a revised edition of this book, in which still more useful information about insect pests may be given. E. G. SLY, Officiating Inspector-G eneral of Agriculture in India. The 1st May 1906. PREFACK. THE study of pests in India dates back twenty years to the formation of the Entomological section of the Indian Museum, the commencement of Indian Museum Notes, and the publication of Surgeon- General Balfour's little volume, " The Agricultural Pests of India." During this time a continuous effort has been made to classify insects injurious to crops, terminating with the work of the late Mr. L. deNiceyille, the first Entomologist to the Government of India. It has fallen to me to gather up these records, to supplement them by observation in the field, and to put together briefly what is known of Indian pests. To any one familiar with the scattered records of Indian Museum Notes, such an undertaking was a necessary pre- liminary to further work and, above all, to the wider growth of the study of insect pests. Eew oljservers have contributed to our knowledge of insect pests in India, which is deplorable in so vast a continent where so large a population is depen- dent on agricidture. In the present volume I have tried to give a short account of the general features of the lives of insects, as well as the salient facts concerning our destructive pests. Those who wish for technical accounts of the anatomy and classi- fication of insects will find abundance of excellent books. We are here more closely concerned with their living activities and the part played l3y them in the reduction of the yield of the staple crops of the country. I trust that the book may be of service to many who are engaged in agriculture and horticulture. Insects are universal and quite interesting as soon as one ceases to regard them as mysteries. I cannot hope to emulate the living interest of VI PREFACE. the insect world as presented by '' Eha," but perhaps the necessary precision oO thought and language in this volume may blend with his delightful pictures and help to give a true impression of our insect friends and foes. Much of the local information in this volume has been obtained from the many reports sent in at the instance of the Directors of Agriculture. In a country where nothing is outside the scope of official enquiry, much may be learnt from enquiries pursued by the Mamlatdar or Tahsildar, and especially in regard to the attitude of the cultivator towards his pests. My acknowledgments are due to the many dis- trict officials who have sent in reports of injurious insects and carefully collected information as to the remedies in use among the ryots, I am under a deep obligation to Mr. P. G. Sly, Officiating Inspector General of Agriculture, to whom the inception of the book is due, and ayIio lias endeavoured to bring the arransrement and text into the form most suitable for those for whom it is intended ; without this encouragement and advice, the volume could not have been produced in its present form. I have also to thank Mr. 0. A. Barber, Gov- ernment Botanist, Madras, and Dr. H. H. Mann, Scientific Officer to the Indian Tea Association, for valuable help and suggestions in the final preparation of the text. The illustra- tions are largely the work of the late artist in the Indian Museum, Babu G. C. Chukraburtty, and these have in many cases been published in another form in the pages of Indian Museum Notes. Others have been prepared under my super- vision by H. H. .Deboo, Chotalal Daulatram Shah and Eambliau Balajee, artists attached to the Department of Agriculture. The diagrams and photos are my Qwn, and Mr. H. C. Wood very kindly prepared tlie design on the cover. I am indebted to the work of my staff for many observa- tions ; the Entomological Assistants attached to the Depart- ments of Agriculture in the Punjab, Central Provinces and Baroda have added inrormatioii concerning' injurious pests, and I have incorporated their o])servations in some cases. I trust that many will be found to follow in their footsteps, to take up the study of insect life in relation to agriculture in India, and to devote themselves to this In'anch of research. It is certain that India should not be behind other nations in scientific knowledge, and that men can be found who will devote themselves to this form of learning, not for the sake of the pay or position, bnt at the bidding of that intense organised curiosity which lies at the root of modern science. I venture to hope that this volume may draw others into this work and open a new field for research. H. MAXWELL-LEFROY, Imperial F.tiiomolofjiat. CONTENT'S. Part 1.— Insects in General Chaptek I. — Insects : their structure and food . „ II. — Life history and habits .... „ III. — Form and colour ..... IV. — Classification and nomenclature Fage 1 15 34 52 Part II.— Preventive and Remedial Measures. Chapter Y. — Origin of insert pests . . „ TI. — Preventive and remedial measui'es „ VII. — Insecticides and spraying Part III.— Insects Injurious to Crops Chaptee "VIII. — Pests of the cotton plant „ IX. — Pests of rice and wheat „ X. — Pests of cane, maize, and sorghum „ XI. — Pests of leguminous crops „ XII. — Pests of miscellaneous field crops „ XIII. — Pests of vegetable crops XIV.— Pests of fruit . „ XV. — Caterpillar pests , „ XVI. — Beetle pests . . . „ XVII. — Locusts, gi-asshoppers, surface beetles, and burrowing insects „ XVIII. — Sucking insects ........ 63 68 75 89 114 125 140 151 163 170 181 196 210 233 Part IV.— Other Important Insects. Chjptek XIX. — Insects infesting grain „ XX. — Insects attacking cattle ,, XXI. — Beneficial insects Appendix A. — Useful informaiiou „ B. — Collecting, pinning, setting 251 261 268 283 290 Ge>-ekai Index 305 List of Illustrations ......... 311 List op Plants ........... 315 Part I. INSECTS IN GENERAL CHAPTER I. Fia. 1, A Millipede — {not an insect). INSECTS : THEIR STRUCTURE AND FOOD. THE word insects recalls the many familiar butterflies, beetles and other flying or crawling- creatures that are so abundant. The term is, however, very loosely used and inchides many crawling" creatures that are not insects in the strict sense of the word, and with which this volume does not deal. It is not easy to give a clear idea of the animals included in the great class Insecta. Excepting" birds and bats, insects alone can fly; but only a proportion of the insects one commonly sees have reached the flying stage or ever fly. We must, therefore, look for better distinguishing characters. The legs will help us. A great host of small creatures that crawl on earth have distinct small jointed legs. One thinks of spiders, of centipedes, of millipedes, of scorpions, as well as of beetles, caterpillars and the like. Of these, in- sects have never more than three pairs of legs. A centipede with over 40 legs is not an insect, nor is a milli- pede. A spider with four pairs is not an insect, nor is a scor- pion. On the other hand, a caterpillar is, though it seems to have many legs; Pjq 2 actually it has three Bed Spider— {not an insect). pairs of little jointed 2 INSECTS : THEIE STRUCTURE AND FOOD. legs, but also has five pairs of little sucker-feet to enable it to crawl along a leaf. Our insects then, if they have no wings, should certainly have not more than tliree pairs or six legs. They also have the feelers on the front of the head. Fig. 3. Ti/pical Caterpillar. But on the other hand there are maggots, for instance, that liave no legs. They look like worms, but are distinguished by many small points of structure. One can only remember that a maggot is one stage in the life of an insect and will become a fly with wings and six legs. There are also insects that have anything but the general form of insects; they are however rare, and if we keep clearly in our minds that spiders, centipedes, millipedes, scorpions and such -like eight or many- legged creatures are not insects, we are not likely to be confused. For those who want a more exact and scientific definition, there are excellent books on zoology and comparative anatomy, where the distinctions are expressed in more scientific terms. An insect's body is completely clothed in hard durable material within which the organs He. This is not one continuous covering, but is formed of rings joined end to end by flexible connections so as to enable the insects to crawl and move about. These rings overlap a little and so present an un- broken hard surface to the outside. Within this flexible tube of rings lie the soft parts, the muscles, nerves and all organs ; attached to it ax'e the legs, wings, jaws, and other parts. Fig. 4. An insect (beetle) which resembles a mite, but has three pairs of legs. INSECT STRUCTUKE. If we take a caterpillar and examine it we find the following- parts : — The head is rounded, broadly attached to the body ; the mouth is situated on the lower side with a complex arrangement of jaws ; small THO'RA X # nooTH i-fs ^/ > iTi^Acie fce-r Fig. 5. eyes are set in a half circle on each side of the head ; and we may dis- cern a pair of small feelers called antenna. Behind the head are three segments (a ring" and the contents are called a segment), each having- a pair of small jointed leg-s below : there are short or long- hairs on each segment, and the first segment often has a small oval shield just behind the upper part of the head. These three segments together form the thorax. Behind the thorax are eight segments (which form the aid omen) ^ HEAD ANTENNA > THORAX. • ABDOMEN MOUTH SPIRACLE. SUCKER FEET .SPIRACLE Fig. 6. JHagrc^m of Caterpillar. P % 4 INSECTS : THEIR STRUCTURE AND FOOD. and the last ono ov two wl.icl. wo may call tlio tail. Tlieso segments are nearly alike, but the four in the middle usually have a pair of small projeetions on which are hooks ; Ihese are sucker-feet and there is a fifth l)aii- on the tail. Each of the eight segments has a small dark spot on each side, and a similar si)ot is found on the thorax ; these s]wts are Higmata,'^ or air openings, which admit air to the system of air tubes inside the caterpillar^s body. The hairs or bristles found on the segments and the tail are not scattered haphazard, but arranged in a definite manner. These are the salient points that can be seen in any insect. In all insects the head, the thorax and the abdomen are distinct ; the head always bears the eyes, the mouth and jaws and the feelers {antenna) ; the thorax always bears the legs and the wings and is actually composed of three segments, though we cannot always see the division ; the abdomen bears sucker-feet in some insects only and has a varying number of visible segments in different insects. Stigmata, or air openings, are found in all insects, and usually are arranged as in the caterpillar. AH insects have a more or less hard covering, which is composed of a substance known as cJdtin ; this is a nitrogenous material, peculiarly resistant to chemicals, which forms an impervious covering. The legs, antenna?, wings and all parts of an insect are covered in it ; the thick hard wings of a beetle, the fine scales of a butterfly and the flexible sldn of a caterpillar are largely composed of it. Speaking generally, the skeleton of an insect is this outer covering; there are no "bones,^' but a few chitinous supports of the internal organs. When an insect is killed and dried the whole body perishes except the chitinous covering, so that a pinned collection only consists of this dried cJiitin. Such insects as have not a suffi- ciently thick covering must be kept in spirit, so that the internal organs may be preserved in order to maintain the natural form of the insect. Fig. 7. A Wasp, showing the divisions of the body in a winged insect. Stigma, a spot ; plural, stigmc^ta, spots. WINGS AND MOUTII-l'AllTS. Fig. S. Fit/, to show the second ijair of loings reduced to halancers. In distinguishing' the different classes of insects, it is necessary to look specially at the wings and the mouth-parts. In mature insects there are, as a rule, two pairs of wing's : the first pair (upper or fore- wings) attached above the second pair of legs, the second (lower or hind wings) attached above the third pair of legs. In some insects the second pair of wings is not present or is transformed into a different structure. In a few the wings are never developed, the mature insect being wing- less or having imperfectly de- veloped wings, (rigs. 10, 30, 40 and 51.) The " mouth-parts " (jaws) of insects are the structures that surround the mouth and which are used for feeding. These structures are somewhat complicated and are specially formed in accordance v/ith the habits of the insects. Insects that bite leaves or green plants have short bit- ing mouth-parts, with cutting teeth ; insects that attack other insects have usually long sharp jaws, suit- ed for grasping their l)rey ; those which suck the juice of plants have a slender tube-like beak, with sharp instruments for piercing the plant ; those also which suck the blood of animals or insects have a sharp tubular beak, as in the mosquito. It is important t(^ be able to recognise the differences between these kinds. A few have mouth-parts not included in either of the above kinds ; thus the bees have very complicated jaws, which are litted for lapping up the nectar in Fig. 9. Head of a Caterpillar, from heneafh. {From Lijonnet^ iifSfeCTS : TUEIE STRUCTtPvE AND FOOt). Fig. 10. Three carnivorous Beetles ivith long mandibles. flowers and also for biting' ; tlic butterflies and moths have moutli-parlis formed like a long slender tube whicli can be stretched into the bottom of flowers to extract the nectar. Figures 11 — 15 will show the appearance of these mouth-partsj and it is important to look always at the mouth-parts of insects, since this at once gives a clue to the probable habits of the insect. MOUTH-PAHTS. ... C. Fig. 11. The biting mouth-parfs of a CricTcef. a. Vpferlif. b. The stronr/ toothed mandibles, c. The sensoru palps. Fig. 12. The biting mouth-parts of a Beetle. a. Upper lip. b. The strong curved mandibles, c. The'sensorg palps. Fig. 13. The sucking mouth-parts of JDiptera. Fig. 14. The curled -up proboscis of a Butterfly. Fig. 15. The curled -up pro- boscis of a Moth. 8 ilsrsEcf s : tSeiu structure and pood. The bodies of insects are made up of muscles, nerves, organs and other parts just as other animals are, and they live in a very similar way. The food taken in at the mouth passes into the stomach, and is dig-ested ; the remains are excreted. The stomach and intestine form a plain long tube which passes from the mouth to the tail. The digested food passes into the space between the skin and the intestine, in which all the muscles and nerves lie ; above the stomach and intestine there is a small heart, consisting of a long slender tube which pulsates and pumps the dissolved food forward over the head and all round the body ; this can be seen in many caterpillars, if the upper part of the body is intently watched for some minutes. In the body there are numerous muscles, which enable the insect to move. In the head there is a small brain, and running down the lower side of the body there is a double cord of nerve tissue, with little swellings in each ring. This cord is like our own spinal cord, and from it nerves go to all the parts of the body. Insects have nerves similar to our own though on a simpler scale. Besides these organs, the perfect insect has reproductive organs, male or female. These open at the hind end of the body, just below the opening of the intestine. In many insects the female has attached to the hind end of the body a special instrument for laying eggs ; the sting of the bee is really the egg-laying instrument : in some insects this structure, called an ovipositor, is very large and conspicuous (fig. 52). Insects have senses and sense organs which we may compare with those of other animals, though we cannot pretend to understand them. Eyes take the form either of a pair of large conspicuous structures on the side of the head or of several small points on the upper surface or side of the head. The former, known as compound eyes, we may consider as hundreds or thousands of small eyes united to form a single complex structure ; we can see these separate small eyes which give the whole eye a honey-comb appearance. The latter, known as simple eyes, are found in caterpillars and other immature insects, whicli do not have compound eyes, and also in many mature insects in conjunction with compound eyes. The caterpillar has five or six such eyes on each side of the head ; the grasshopper has three only, some bugs have two, and many insects have none. The function of eyes is not clearly understood, but it is believed that the compound eyes are as efficient as our own eyes, and that simple eyes perhaps serve to distinguish light and shade or act in some such simple manner. '^ Organs of hearing are present probably in many insects, but definite organs similar to our ears are known only in the grasshoppers and their allies. Many other insects probably hear sounds, since many of them also make sounds, but it is not certain what is the organ of hearing. SENSES. 9 The sense of smell is also probably present, and is believed to lie in the antenna3. Some insects [e.g., locusts) can almost certainly smell water, a feat we are incapable of because our olfactory organ is always damp. Others can certainly smell flowers, carrion, etc., and their sense of smell is probably far keener than our own. Taste is believed to be a sense functional through certain organs in the mouth-parts. Touch is another sense probably connected specially with the antennae and the little palps on the mouth-parts. Other senses that we do not now use certainly occur ; possibly we were once possessed of the " sense of direction," as many insects are ; other obscure senses we are able dimly to perceive only after a close study of the habits of insects, although we cannot connect any special sense organs with them. Among these we may include the very peculiar sense shown in the phenomenon known as '^ assembling." It is known that if the females of certain moths are exposed in a cage, the males of those species will come in numbers and from considerable distances. These dis- tances in some cases extend to several miles. By what sense the males become aware of the presence of the female is not known. The pheno- menon is utilised in the rearing of wild silk moths in India, the reared female attracting the wild males from the jungle. It is impossible to discuss the senses of insects in further detail in this book. Man cannot hope to comprehend them. The fact that a butterfly knows " by instinct " the i^lant on which its young will feed seems marvellous when we recollect that the butterfly could not remem- ber what it fed on as a caterpillar, the metamorphosis having come after its caterpillar stage and obliterated its memory of larval life. There are countless instances of this kind, and we can only study the activities of insect life with admiration at the wonderful "instincts" and senses with which they are endowed. Among other curious phenomena may be marked the formation and migration of swarms of insects, such as locusts. Tliis phenomenon is also little understood ; it occurs in a small number of insects belonging to different families. The locusts are the best known instances in India, two kinds of which move in swarms over many hundreds of miles. It occurs also in moths, butterflies, dragon-flies, in the larvie of certain flies and in^caterpillars. Large numbers of these insects gather together, form swarms and migrate from place to place. This phenomenon probably originates in the necessity of moving to fresh places in search of food. Insects which multii% very rapidly into enormous numbers may have found it a necessity to move often, the habit thus becoming a settled one. 10 INSECTS : THEIR STIiUCTUEE AND FOOD. Food. From the moment that an insect hatches^ its first task is to provide food by its own exertions ; it has also to escape the enemies and dangers that surround it ; lastly, it has to lay eggs in the proper situation and in some cases must provide for the young. These are the three prime neces- sities of the insect^s life, and though in many cases it is possible that the gratification of a taste for other pleasures is an object in life, we may interpret the activities, the form, colour and structure, even the life history of insects in terms of these three principal needs. The food of insects is extremely diverse, and it is not always clear how they are able to extract the requisite amount of nutriment from the substances they consume. We may at once abandon the idea that nutrition is comparable to that of domestic animals. Digestion, nutrition and respiration are very different in insects. What proportion of proteids, carbohydrates and fats is necessary cannot be stated. The amount of food or of air necessary to existence may be reduced to very low limits since insects are not Fig. 16. warm-blooded ; in the absence of muscular Wingless Perfect Insect : the activity there is probably uo wastage of the insect lives on the surface of the . •• it „^,r^-„-, n/^ sea and has no need of toings. tissues, no consumption of oxygcn, no {From Distant) elimination of water or of waste |)roducts. The amount of food or oxygen assimilated may be measured by muscular activity and may cease entirely when this ceases. Bearing this in mind, we need not be astonished at the insects which live solely in dry wood, in burrows without access to the air, or which feed solely on chillies, opium or tobacco. Such insects do not drinlc, they simply eat, and we are entirely ignorant of their digestive and nutritive processes. Nor is it astonishing that many insects can live for many months without food. Most insects live on land, a few on or near the sea, many in fr>sh water. Marine insects are few -, some in the sea itself, some on the surface, a larger number on the beach or in rock-pools. Eelatively, the number is very small, and sea water presents an almost impervious obstacle to insect life. Fresh-water ponds, streams, tanks, and other supi^lies bOMINANCil. 11 o£ water teem with insect life. Their habits are of great interest, and the devices with which they supply themselves with air are amazing* in their diversity and ingenuity. Unquestionably the aquatic insects are descended from air-breathing land insects, and for every species the problem of extracting air from the water or of di'awing a supply from the surface has been solved in a more or less ingenious manner. These insects, how- ever, form a division apart, cut off by their diverse habits from the insects living on dry land. The vast majority of insects live on the land, establishing them- selves in every possible situation, with the most diverse occupations and methods of obtaining a living. At this period of the earth^s history they are the dominant group, the most successful and prosperous, taking toll of all other creatures. In number of species, in actual numbers or bulk, in the sum total of their activities, they outweigh all other forms of animal life at present on the earth. The extraordinary diversity of their habits and food, their rapid multiplication, their small size, their varied powers of locomotion, of offence and defence, and the marvellous instincts and senses with which they are endowed, all these serve to put them above other forms of animal life. Man prides himself on conquering nature, on being the highest expression of animal life, the crown of crea- tion : a dispassionate examina- tion of insect life reveals that even man's powers are as nothing to those of insect life, his senses weaker, his sociology and conduct of life far inferior to that of the social insect, and he himself com- paratively lacking in the exhibition of altruism and right conduct shown by an insect. Insects are small and their domination is not ajiparent; but they have established themselves in every nook and corner of the earth, deriving their food from a vast number of sources. Many feed on plants, living in every part of the growing plant, from the fruit to the roots ; eating the flowers, boring in the stem, mining in the leaves ; they devour the leaves, destroy the bark and ^<; ^ h -""■■■^ '-..• \ a '^ Fig. 17. Piaffes of Fly ivhose maggot lives in the leaf of the tea-plant, {From drawing hy E, E. Green.) 1 2 INSECTS : THEIR STRtlCTUHE AND POOD. eat the roots ; tliey suck out the sap and live as parasites upon all parts of the plant. Perhaps one-third of the total number of insects live on plant life directly, thus constituting one big" division called the Herbivores. There are others which live on the dead or decaying- plant, on dead leaves, on rotting fruits, on dry timber. Any vegetable tissue that is no longer alive and growing furnishes food to this division. We may include with them the feeders on decaying animal tissue, such as the dung feeders, the carrion beetles, the corpse buriers. We may term them all Scavengers, since they, with the bacteria and fungi, cleanse the earth of its rubbish and convert it into good plant-food again. They also form a large division, not less important but far less visible to us, work- ing in the dark and in hidden places. As the plant world furnishes food for so many insects, so also these insects in turn are fed on by others, and we find a very large division which get their food from the herbivorous and scaveng'ing insects or from each other. These work in two ways, by preying upon insects and eating them bodily, as a tiger eats a cow, or by living within their bodies parasitically, as a tapeworm lives in a horse. The former, the Predators, we see daily at work and we may compare them with the many insec- tivorous birds. The latter, the Parasites (Ichneumons and flies), are not less numerous and abundant ; their larvae live in the insect, absorbing the food laid up by the host and gradually killing it. The two groups together check the immense increase of insect life and form the third great division. There are also a small number of insects that live parasitically in or on warm-blooded animals. They feed on the blood of man, cattle, wild beasts, birds and other animals, or live parasitically within their bodies. They form a small division. There are lastly the insects which have found that man offers many comfortable homes in his houses and buildings ; they live upon grain, flour, drugs, all manner of produce and household stores ; they inhabit our houses, deriving a precarious existence from what they can pick up. These are the household pests ; they have been carried in ships to all parts of the world and established themselves wherever man is. This division is not large or very important but an aberrant and distinct oli'shoot from the great scavenger class mentioned above. We have now included practically every insect in our divisions, and if we subdivide them, almost every species whose habits are known would flt in. We see the part each plays in the great cycle of life. The herbivores feed on the plants, which build up organic matter from the soil and air under the influence of the sun. These herbivores build up the plant tissue FOOD. 13 into more eomplox ovoj-anic eomponnds and in turn supply food for otliors. The scavengers feed on the decaying plant life and animal Me, clearino- the earth of deeayino' refuse, making- it clean and sweet ; eventually they die and the Avhole mass of organic material breaks up into the compounds available for plant life. The parasites and predators feed upon the living insects, checking the increase of both herbivore and scavenger, so that the destruction of living plant life by herbivores can then never go beyond a certain point, the balance thus being maintained. We are in this volume mainly concerned with the herbivorous insects, those which feed upon the living plant. They are largely injurious to man, though also beneficial. We cannot neglect the parasites and predators, for in actual work we meet them at every turn ; the part they play is not very evident, but the practical study of pests requires that every student of agriculture should be familiar with them and recognise them almost at a glance. The scavengers are not of direct importance and we see them but little ; grain aud household pests are of direct importance to man as also the insects parasitic upon cattle and warm-blooded animals. Food Plants. Caterpillars and other herbivorous insects may have one, a few, or many plants on which they can feed and thrive. Evidently an insect that can live on a variety of plants has an advantage over one that lives only on one or a few, and injurious insects are largely those which have a great range of food-plants, enabling them to spread widely, to increase abundantly, and to find food when crops are not available for them. The list of injurious insects is nearly synonymous with the list of insects having many food-plants. In general, insects feed upon one or more closely allied plants ; thus cotton pests are found also on hUnda and other species of Hibiscus, cane pests on maize and sorghum, and so forth. In other cases they feed on plants which bear similar fruits ; an insect that eats tlie oily seeds of cotton will perhaps feed on the oily seeds of other plants not closely allied to cotton. The food-plants of some species, e.g., the gram caterpillar, are to be numbered in scores. The food-plants of others are few, and there are insects, for instance, which can feed on certain varieties of cotton aud not on others. The composition of the tissues of the plant probably determines its suitability to insects, and some plants appear to have no pests. Plants protect themselves in various ways, but insects in their turn seem equally to accustom themselves to the oils, alkaloids, hairs. 14 INSECTS : THEIR STRUCTURE AND FOOD. thorns, etc., with which plants have tried to render themselves safe. Modern science has not yet discovered any method of altering the com- position of plant sap so as to render it distasteful or poisonous to insects. When this subject has been mastered, we shall be in a position to deal more siicccssfnlly with insects by purely preventive methods. CHAPTER II. LIFE HISTORY AND HABITS. INSECTS pass thvoug-h various chaiig-os diirino- thoir lives, ehan^^es of form, habits, structure and the like ; these transformations are in many cases very g-reat, being- the most striking- characteristics of the life history of insects. Whilst the life history is essentially the same through- out larg-e groups of insects, it is not exactly the same in any two species. We can g-ive here only a very brief outline, but fuller details will be found in the later sections. Insects are hatched from eggs, which, though smaller and different in appearance, are essentially similar to those of birds. These eggs arc not cared for by the parent insect, but are laid in such a position that the young when they emerge will find suitable food. From the eggs hatch out tiny insects which are usually able to feed almost at once and begin their active life without delay. They feed voraciously and rapidly grow larger. Their cliitinous skin will, however, not stretch and permits of growth only to a certain limit ; when this is reached, a new soft skin is formed under the old one ; the latter splits so that the insect crawls out with only the new soft skin ; the insect at once expands, the new skin hardens with the result that our little insect is suddenly twice its previous size and perhaps very different in appearance. Growth again continues until the insect is too large for the second skin, when the process is repeated and a fresh moult undergone. The skin is thus shed periodically until the insect attains its full size and mature form. At every moult the appearance of the insect changes ; it may be a minute change in appearance with a considerable change in size, or it may be a com- plete change of form, with change of habits and structure. The number of moults varies from two to twenty or more, but is generally about five to seven. These changes form the essential part of the life history of insects. We can now examine in detail the nature of the changes ^^*^' ^^' J • ii J c • , £lo(JS of a Butterfly; natural undergone m the great groups of msects. Ze on a leaf, and enlarged. 16 LIFE HISTOUY AND HABITS. If we patch a female butterflj^, for instanee, ilie very enmmnn one that is fio-ni-od (fio". 24) and keep it in a suitable eage, it Avill lay eowp. These eg-o-s are shown in figs. 19-30 much mag-nified, and in another fionirc (fio-. 18) are showai the eggs of another butterfly both mao-nified and natural size. The eggs are small white seed-like things and laid singly on the leaves of a plant. If we keep these eggs, they will presently hatch into caterpillars (fig. 21) ; these are somewhat worm-like in appear- ance, with legs and sucker-feet, totally different from the butterfly Fig. 19. Fig. 20. Butterfy Ff/g. {Magnified.) Fgg after Caterpillar leaves it. {Magnified.) in habits and structure. These caterpillars eat the leaves of the plant and moult as they grow larger; at each moult the colour chang-es very slightly, and the caterpillar comes out much larger. There are five such moults, and at the end of twelve or fifteen days the caterpillar has attained to its full size (fig. 22). It now ceases to feed, becomes im mm'' wWff ■wi = 'H\ Fig. 21. Young Caterpillar. Fig. 22. Fiill grown Caterjrillar. uneasy ; it is preparing for another moult. To do this it fastens a small pad of silk at some point on the leaf of the plant, and fixing' the hooks of its tail sucker-feet in the silk, hangs itself head downwards from the pad of silk. The skin bursts and is thrown off and the insect is seen hanging" from the leaf. It is now completely changed in appearance and is called a chrysalis ;' it is a rounded, green object, with pretty gold markings (fig. 23) ; there are no limbs, no mouth, no eyes ; spiracles alone can be seen. This curious creature hangs motionless from the plant for * Chrysalis]; plural chrysalides. LIFE OF A BUTTERFLY. 17 six days, taking no food and appearing- to be asleep. At the end of six days, the outer skin bursts, and a larg-e insect comes out. This walks feebly about for a few minutes whilst its large wing-s expand and spread out; these wing-s become firm and stiff and we see that it is the butterfly again (fig. 24) similar to the one first caught. This butterfly will fly away, mate and again lay eggs, which will again hatch to caterpillars, the cycle beginning again. This is a very short descrip- tion of what occurs in the life of this butterfly and similar Fig 23. Chrysalis of the Butterfly. changes take place in the life of every butterfly. We see in it four stages— the ^g^, the caterpillar, the chrysalis, and the butterfly. During the q^^ stage the caterpillar is formed from the germ; the caterpillar feeds, grows larger and moults; at each moult the^re are only small changes, and during the growth in size, covering five moults, Fig. 24. Butterfly. the insect changes but little; its whole business is feeding, growing larger, and lading up a store of fat. When the caterpillar is fulfgrown, P 18 LIFE HISTOEY AND HABITS. tlie big cliang'e takes jalace ; for this it jireiDares by hauging" itself in a convenient place, out of the way of enemies, etc., and becomes the chrysalis. During this period an internal transformation takes place and the tissues of the caterpillar build up the butterfly. There is no process akin to this in any domestic animal with which we are familiar ; every part of the caterpillar is built up anew ; the internal organs are remodelled; wings are formed; long legs take the place of the short caterpillar legs ; the biting jaws of the caterpillar have been thrown off and the long tubular proboscis of the butterfly is formed ; new compound eyes are formed ; new sense organs appear. Further, the entire repro- ductive system of the butterfly is built up and formed. Only the beginnings of a reproductive system are to be found in the caterpillar, but' a more or less complete and complex system of rej)roductive organs, male or female, is formed during this stage. When, at the end of six days, the butterfly within is fully formed, it emerges; the skin is soft, the wings soft and folded up; in a short time the wings expand, become hard and dry ; the body takes on firmness, the legs become stiff, and the butterfly is ready to fly away, with new senses, new instincts, to suck the nectar from the flowers, to find its mate and to flutter gaily in the sunshine — a change as great as we can imagine from the crawling caterpillar that hung itself up six days before. The life of all insects is not exactly similar to that of the butterfly, and we may take the life of a grasshopper as an example of what changes take place in some other insects. K'^^W^ > 1 k. ^^ W r \'W ^m w^ •^ m'' y l'-# J LP^ ^4 ^■^ Fig. 25. Iig(j mass detiic//('i/, Fig. 20. lEf/ff 'jiiass in ff round. LIFK 01' A GlfASSIlOlTEl!. 19 The female grasshopper lays amass oP eg-g-s (%s. 25, 20) in the ground and shortly after dies. These cg'gB lie in the ground for some weeks and presently each splits and a young- insect comes out. This young" insect is very small, about twice the length of the egg's, and very active. The general form is like that of the parent ; there are the long legs, the hind pair very large (fig, 27), and the head like that of the grasshopper with similar antennte and jaws. But there are no wings and the little insect can only leap. It is also quite distinct in colour. It feeds upon green plants just like its parents did and grows larger. Moults take place as in the caterpillar, and at every moult the insect comes out larger and somewhat differently coloured. At the fourth moult (fig. 28) two lobes appear at the upper side of the body, on the second and third segments of the thorax, above the second and third pair of legs. At each later moult these grow larger until with the sixth or seventh, they take Fig. 27. Yonnrf Insect, one daij old. iimes.) (Mar/nifled five Fig. 28. llalf-groivn Insect. (Mar/ n ijied twice.) the form of the large perfect wings. Our grasshopper (fig. 29) is now full grown and moults no more. It has perfect wings, a fully developed reprodiTctive system, and will presently mate, lay eggs and die. This life history is a great contrast to that of the butterfly; the young is like the parent in general form, feeds in the same manner and ao LIFE HISTORY AND HABITS. lives a similar life. At each moult it grows larger and gradually changes, almost imperceptibly, till it is full grown. There is no caterpillar, no chri/salis ; there are no sudden changes at any moults ; the wings grow slowly ; the reproductive system is developed gradually ; there is no period of rest, and the insect feeds at every stage of its life. We may concisely state that whilst the grasshopper develops gradually, the butterfly does so suddenly. The sudden change from caterpillar to chry- salis, and chrysalis to butterfly, is one distinguishing feature ; this is called the mttamorpliosis, and all insects which pass through these changes are said to have a '^metamorphosis.'^ It is a convenient word which expresses the facts that (1) the young insect is totally unlike the mature insect ; (2) between the two is the resting stage similar to that we call chrysalis. We might divide all insects into two groups, those which are caterpillars and chrysalides before they become butterflies, and those which change gradually and slowly till they become grasshoppers. The first have a metamorphosis, the second have none. Speaking gen- erally, all insects belong to one group or the other. They either have €tiX> Fig. 29. The 'perfect Insect. metamorphosis and pass through four stages, viz., (1) the q^^ ; (2) a stage like the caterpillar (called larva) ; (3) a stage like the chrysalis (called p2cpa) ; (4) the mature stage like the butterfly (called imago) ; or they have no such distinct stages but commence as eggs, pass through a series of gradual changes during wdiich we may call the insect a nijm'pli, to the perfect insect, called the imago} It will be seen that we have here a character that sharply divides all insects into two groups. There are some insects which have a partial ^ Larva, plural larvae ; jpupa, plural pupa ; imago, plura] imagineft ; nymfh, plural nymphs, ' ' ' MK'rA]iioiil>Hclsisi. iii Fig. 30. A wingless mature CocJcroach. metamorphosis aud which are really intermediate between these two groups; but they are not common aud Ave arc unlikely to meet with them. We shall find large and distinct groups of insects which have a metamorphosis, and equally large and distinct groups which have none ; every student shoidd know at once whether an insect has or lias not :i metamorphosis. Before proceeding to the next sec- tion, we may draw attention to a few points. All perfect insects, i.e., ima- gines, have wing's, or should have ; there are many exceptions to the rule and in many insects the wings are not fully developed. This is more common in insects which have no metamorphosis than in those which pass through the pupa stage. Such insects which look immature can be known as mature if seen coupling. None but imagines, i.e., perfect insects, can couple or reproduce. On the other hand, any insect with fully developed wings, i.e., with wings with which it can fly, is an imago and will not grow any more. A small flying grasshopper cannot be a young locust or become anything else. A small beetle cannot grow into a large beetle. Whatever its size, a winged insect is full g*rown and will not do more than lay eggs. This is an absolutely invariable rule. In later paragraphs, the life history is stated in greater detail and some of the many exceptions to general rules are discussed. In entomo- logy, as in all other branches of biology, the general rules are abundantly proved by their exceptions. There are very few general statements that can be made to which there are not many exceptions. We can say generally that all insects are hatched from eggs, but there are very numerous exceptions ; equally we can say generally that mature insects, like other creatures', are of two sexes and that the process of reproduction is dependent upon both sexes ; even this statement is not true of all insects. It is necessary to guard against hard-and-fast rules and generalities in dealing with infects ; they are valuable as aids to memory and the imagination, inevitable in class rooms and books, but they must be carefully used outside the class room. Nature has no cast-iron rules, and the more we study nature the more we find an infinite variety that laughs at our generalisations. One group shades into another ; the habits of one class are linked to those of another by insensible gradations ; no tAvo species a2 LIFE HISTORt AND HABITS. are alike iu form or habits, so that we must have a c-lear coiiceptioii that we are not in a world o£ clear-ent definitions and distinctions but in one whose first charm lies in its infinite variety. Eggs. Insects are not produced spontaneously from plants or from dirt, but arise from eg-g-s laid by the parent insect, or, in rare cases, are born alive. No case is known of insects having been produced in any other way, and in tracing the life of an insect we may commence from the time the parent lays the egg. Insects often appear suddenly in great numbers, and ignor- ant cultivators believe that they have fallen from the sky or are due to a change of weather or some similar cause. The appearance of an insect in small or large numbers is not a supernatural phenomenon and can only be caused by the parent insect having laid eggs or j)roduced living young in or near that spot at some earlier time ; the eggs may not have been seen and may have been there for several months, but in every case if Ave could go back far enough we could trace them to the parent insects.. Eeproductiou in the insect world is a process similar to that of the higher animals and no more mysterious; it depends upon simple causes which are fully capable of investigation and differs but little from those which bring about reproduction and multiplication in other living creatures. In almost all cases, the eggs are produced after the mating of the male and female insects ; there are a few groups of insects in which males occur rarely or not at all ; the females then produce eggs or Hving young without the co-operation of the males, but this is confined to a small number of insects and in them occurs regularly. If a bred female moth is kej)t alone in- a cage, she may lay eggs, but they are imperfect and do not hatch ; an aphis, on the other hand, may produce eggs or. Hvin^ young without any male being present, many successive genera- tions being thus produced without the intervention of any male. In some groups, insects are born h,livc. In the ajj hides this is the normal process during part of the year, no eggs being formed, but the virgin female producing living young. In some flies, the female carries the fertilised eggs within her body awaiting a suitable opportunity to lay tliem on sufficiently decayed matter^ Fig. 31. Coclroach T.gg case. {Mar/vified.) EGGS. 23 and these eggs often hatch before they are laid, the Hy then depositin"- living- maggots. These phenomena oeeur rarely in other insects, being exceptions to the almost universal rule that insects hatch from eggs. Eggs are usually laid where the young will find abundant food and are then abandoned hy the parent. Exceptionally the parent cares for and watches over the eggs ; this is the case also in social insects, but the eggs are then more usually looked after by special individuals and not by the parent. In most cases the parent dies soon after the completion of egg-laying and the young that hatch live an independent life from the moment they emerge. The beautiful instincts of the digger wasps are perhaps the best instances of maternal care for the young (see page 271). The number of eggs produced by the individuals of any one species is usually fairly uniform, but varies very much in different species. The large Six-spotted Ground Beetle (fig. 344) produces one large egg at a time and produces only a few in its life ; other beetles produce them singly and generally lay only a comparatively small number, but the tortoise beetles. Fig. 32. "Eg;] case and youvg of Mantis, llie latter marjuljied. for instance, produce many and may lay them in beautiful egg cases. Generally beetles' eggs are laid singly and are hard to find. Moths lay many u LIFE HISTOE"X AND HABITS. eggs, usually upwards of one hundred, in clusters or masses. Butterflies lay them singly and in great number. The queen -bee produces a vast number of eggs, laying them singly in the special cells. The locusts and larger grasshoppers lay about one hundred eggs ; the smaller grasshoppers some fifty or so. The Neuroptera lay many eggs, as do the Ort/iopfera.^ It is probably correct to say that insects which are exposed to enemies lay many ei^gs to allow for the inevitable destruction of the majority of the young, whilst " safe forms,''"' which live in hiding or are exceptionally well protected from dangers and from enemies, lay a few. The form of the eggs varies very much in different families. Cock- roaches lay eggs (fig. 31) in a single case of peculiar form, as do the mantis or praying insects (fig. 32). Stick insects drop, one at a time, peculiar seed-like eggs with lids. Locusts and grasshoppers lay a mass of long oval eggs in the ground and green grasshoppers lay them in the tissues of plants. The eggs of the Lacewing (fig. 332, page 27-i) resemble grains of rice and are set each on a stalk ; many other Neuroptera lay masses of eggs in fresh water. The eggs of H^mennptera are small, soft, white bodies, sometimes stalked. Butterflies lay round seed-like eggs, beautifully ribbed ; moths lay similar round or flat eggs usually ornamented or marked. The eggs of the common flies are cigar- shaped, deposited singly or in masses. Bugs often lay neat cylindrical eggs with lids, depositing them in batches ; the eggs of the Red Cotton Bug are round and yellow, laid in the soil, whilst those of the Dusky Bug are cigar-shaped and laid in the lint of the cotton. With such infinite variety, general statements can be accepted only with great caution. The period during which the egg remains before hatching varies immensely according to species, climatic conditions and other factors. The eggs of butterflies hatch in a few days, as do those of mosquitdes ; the eggs of moths hatch very quickly in Avarm damp weather, but dry cold will delay them. Many insects' eggs remain from October or Fig. 33. The eyys of a Plant Bug on a leaf. ^ It is necessary to use srienlific words to designute grcups for which tVere Hie no English equivalents. Ti.e reader will tiud the exphiuation of lhe^e words on pages 62— 54.H:H. Al.-L.j ^ ^ November to the following rains. The Rice Grasshopper^^ i^gs normally stay in the ground for eight months, but will hatch earlier if kept wet. The degree of moisture and heat have a great influence on this period, and little is yet known of the influence of climatic changes on insect eggs in India. Larval Life. When the larva is formed inside, the egg breaks and allows it to emerge. There are special devices for securing the rupture of the egg at the right time, which deserve study. Many caterpillars at once eat the eo-o-shell and then start feeding on their food-plant. As a rule, larviB develop rapidly with a plentiful supply of food and proper conditions. The temperature and degree of moisture play a great part in the growth of the young larvae. Feeding is the sole important business, and growth is rapid. Moults occur as necessary; caterpillars shed their skins five times as a rule ; grasshoppers do so five, six or seven times ; the silkworm does so four times. Many bugs do so five times, though the Mealy Bugs and Scale Insects have only two cr three moults. Some aquatic insects moult as many as twenty times. Though the process of moulting is necessary to allow of continued growth, it has also a physiological reason. The chitinous matter thrown off is nitrogenous and it is probable that the nitrogenous waste products of the body are eliminated in this manner ; insects have no organs which correspond directly to the kidneys of the higher animals, and a part, if not all, of the nitrogenous waste matter is excreted and periodically shed as chitiu. With each moult the form and colour change slightly or greatly. It must not be taken for granted that the number of evident colom- clianges and the number of moults are synonymous. W^e cannot, for instance, collect a great number of the young of a grasshopper, sort them into groups according to size and colour, and then say that each group is the result of one moult ; the changes at one moult may be very slight, though far more striking at every other moult. Moulting is not such a regular automatic process that all individuals of a species have actually the same number, and it has been found that grasshoppers from the same batch of eggs take six, seven or eight moults to attain maturity. Larval life may be very short or very long, depending* upon the habits of the insect, as well as on climatic and other conditions. Generally speaking, development is more rapid in hot weather, slower in cold. There is an optimum temperature, the temperature at which development is most natural, which climatic conditions retard or hasten. There is also an optimum degree of humidity, varying for each species. A rise of tem- perature above a certain point or a fall below a certain point may almost 26 Life histoe^ and habi'is. or entirely suspend vital activities temporarily, and this is determined by the circumstances imder which each species lives. General statements are nearly impossible as they are certain to convey false ideas. Throug-hout it must be remembered that every species of in- sects is distinct from every other species in habits, and that every species has as much individuahty as each human being*, no two species living Fig. 34. Cicada, slightlt/ enlarged. under identical conditions. We can go much further than this, since even species are not well marked and shade imperceptibly into one another, :^^t Fig. 35. A Hairy Caier^iUar, and ils pupa icith the cocoon formed of silk and hairs made ly the caterpillar lefore it lecomes a pvpa. PV?2P,. il Fig. 36. Weevil, and the case from wl/ich it emer as it wriggles out of the hi anch ; moth. d2 X €.u.^ lyoc. C(>//k ct-e. 36 FORM AND COLOUK. whilst the small forms have an enormously rapid power o£ multiplication. In any one species the size is usually constant, but is not a character that can be used to discriminate species. Some species are very variable in size, and males are frequently smaller than females. Fig. 45. Common Cochroach. Form. The fact that an insect^s form is correlated with its habitat and by the necessities of procuring food is abundantly manifest. Insects in general are somewhat cylindrical, a form that allows of twisting- and flexible movements. This jjersists in flying" insects (flg. -iS), as offering less resistance to the air and is also well seen in most larvae. Boring insects are extra-cylindrical, as it were, fitting tightly in the tubular burrows they make or, as in the beetle grubs, having a special cushion-like projection that fits the bnrrow tightly and facilitates locomotion (fig. 88). Many insects are flattened; bark beetles and similar insects that find food between the bark and the wood are often flat, to the extreme of being leaf-like. Ground beetles, cockroaches (fig. 45) and other insects that live on the ground, hide under stones, and run fast, are usually flattened. So too are some caterj)illars (fig. 47) that cling tightly to the leaves of plants, and leaf-miners which find their food between the upper and lower epidermis of a leaf. The tortoise beetles are flat and can cling very tightly to a smooth leaf after the manner of a limpet on a rock. The praying mantises are often formed like a grass stem, and lurk in the grass in the hope of unwary insects mistak- ing them for a grass stem and so getting* Avithin their reach. Others resemble dry sticks and live on dry bushes. The green grasslioppers (fig. 20) for a similar reason are formed so as to suggest a green leaf and deceiAX' butterflies. Mag- „, ,, ' , * . ^ y'ots that live in decaying matter The Buj ^ an example of a Jlal insect. ^ ti {Magnified.) are smooth and Avorm-hke, with FOKM. 37 specially laro-e stio-mata at the tail so that the mao'o-ot may lie embedded in li([\iid and still obtain air. These modifications are necessitated by the search for food ; others Fig. 47. Sliiff Caterpillar, specially adapted to clinri ticjlitlif to leaf. are of use in conferring" immunity from foes. " Cryptic form " is most Fig., 48. Jjeaf Insect. 38 FORM AND COLOUR. commonly associated with cryptic colouring and is seen, for instance, in the stick insect whose long' and slender body is formed and coloured to Fig. 49. Leaf Insect. resemble the twigs amongst which it lives ; we suppose this to he a device to hide the insect from birds. So too in the Leaf Insect (fig. 49) which bears an extraordinary resemblance to a bunch of green leaves. The intensely hard spines found ou some beetles and bugs, the thick coating of hairs (fig. 50), the very thick hard masses of chitin, are believed to make insects distasteful to birds and possibly to predaceous PKOTECTTVE DEVICES. 89 Fig. 50. Spini/ Caterpillar, the spines poisonous, insects. The unpleasant odour of bugs is certainly a protective device ; so too are the bad tasting oils of the blister beetles and ladybird beetles. Some beetle grubs cover themselves in their own excrement, others cany their cast skin. The Lace- wing grub carries a pile of the cast skins of its victims. Stings are probably protective, though birds and lizards eat bees. An unpleasant taste is also probably protective and is associated with the scheme of colouring known as warning colouration. Sex also profoundly modifies the structure of insects. The internal organisation is of course totally distinct and there are com- monly external organs which readily reveal the sex. (fig. 52). Fig. 51. The Med Ant, a wine/less toorker, mature but sexless ; their pungent flavour and keen bite is their protection. 40 POKM AND COLOUE. Fig. 52. Female Long-horned Grasshopper, to show the sword-like oviposilor. In general where there is a diver- sity of sex, the male is the smaller (fig. 53) ; both sexes are frequently similar in size and external characters, the sex being determined only by dis- section. In many Orthoptera the males are smaller and differently coloured, in rare eases being very unlike the female in general appearance. The male stick insects are often winged when the females are unwinged. There is little or no difference between the sexes in Nenroptera. Fig, 53, Male and Female Moth, the smaller male above. Fig. 54. Male Ant, Fig. 55. Worker Ant. (Magnified.) SEX, 41 In many Hf/menoptera tho sexes are very distinct. In the social insects this is carried to a g'reat extreme and we find only a small number o£ individuals with reproductive organs, the majority being- sexless workers (fig's. 51 and 55). In solitary bees and Avasps, there is a distinct male, and in one family the female is wingless, the male Avinged (fig. 40). Beetles display little external difference ; exceptionally the male bears horns (fig. 56) ; in some wood-boring beetles the male is wingless (fig. 86). Fia. 56. 3Iale Stag Beetle, Butterflies display great sexual differences in colour, form, etc. ; we repro- duce one species (figs. 58-59) in which they are very strikingly different. Moths rarelj- display great or noticeable differences, more often small 42 FORM AND COLOUR. distinctions only. Females are in some cases wingless. In flies tliere are seldom striking* differences ; male mos(piitoes have large reathery antennce^ females smaller ones (fig. 00). Bugs are rarely dis- tinguishable^ but some of the predaceous species have clearly distinct sexes. In Aphides, males are often absent ; in Mealy Bugs and Scale Insects, the male alone is winged, the female wing- less and degraded. Male insects commonly produce sounds or songs. Grasshoppers chirp by rub- bing the hind leg along the front wing* ; green grass- hoppers have a powerful Fig. 57. sound-producing apparatus Female Stag Beetle. ^t the base of the wingS. Crickets produce a shrill loud noise. All of these insects also have ears with which to hear the music they produce. Beetles have a very great diversity of apparatus for producing sounds. The best known noisy insects are the Cicadas which live in forests ; they are possessed Fig. 58. Male Butterfltf. SONG. 43 ^ ^ i f 9 r 1 ^4 pi F" .«M^ J ^9fe^^. ' \ jju^ . Fig. 59. Vernal^ Sutterfltj. o£ a complicated sound organ at the base of the abdomen, with which they produce a pecuHarly piercing and shrill noise. A few bugs can Fig. 63. 4 Mosquito, male alove, female leloio. {Magnified.) 44. FOT?M AND COLOTTE. sino- or chirp. Song' is mainly ooncernod Avitli sex and is possibly one of the few means by Avhich the male captivates or pleases the female ; song- may also be connected with the fact that the male is not burdened with the chief care of life^, the satisfactory deposition of the eggs, and so utilizes his superfluous energy in song. Another manifestation of sexual difference may perhaps be found in the luminous insects. Colour. All insects which live in the open air are coloured in a more or less complex manner ; the scheme of colouring is in many species variable within certain limits, but generally is uniform and fixed in all individuals of one or both sexes of the same species. These colour schemes are evidently important to the welfare of the insect, and attempts have been made to elucidate the general principles that underlie them ; no two species have precisely the same form and colour, but large numbers have a similar colour scheme, differing in detail in each species but agreeing in the general effect. We have seen above that some insects, such as stick insects, are so Fig. 61. Mcth on Barh of Tree. An instance of cryptic inarking. formed as to closely resemble their surroimdings and so escape notice ; this is associated with colouring, and the conjunction of cryptic form CRYPTIC COLOUIJ. 46 and colouring' may render a larg-e insect indisting'uisliable from its surrounding's. Leal insects are coloured like a leaf, wliicli may Le "•reen or dry. Many moths (lig\ Gl) sit with expanded wings and the colour scheme blends with the bark on which they sit so well that the moth escapes notice. Others sit with folded wings and exactly resemble bark ; their lower wings are then hidden and may be brightly coloured. Grasshoppers commonly have cryptic colouring, some being dry-grass colour, others green-grass colour, and so on. Grasshoppers that live in the fields and sit on the ground are earth colour (fig. 02) and' have roughened backs like a lump of soil. Cryptic colouring" is very com- mon, usually combined with cryptic form ; it may occur in two different colour schemes in the life of an insect, the change occurring when the changed surroundings make it necessary. Thus a young grasshopper that lives in gi'een gi'ass is gi'eenj but becomes dry-grass colour when the grass ripens and the insect becomes full grown. A caterpillar that sits on a leafy tree is green, per- haps so long as it remains there ; when it has to crawl down the trunk to reach the grovmd and pupate, it becomes brown, as the green would make it conspicuous against the bark of the tree. Those larvse which live in nests or other hidden spots change but little at each moult unless their habits require a change. The changes may be small and imperceptible or very marked, and bear a close relation to the differing habits of the young and the old insect. The same is true of the nymphs of the OrtJioptera and Hemiptera. With every moult there are distinct changes not due alone to the gradual development of the wings and other imaginal characters, but to changes of colour and form necessitated by changing environment. The very young nymphs of a grasshopper, for instance, which live concealed in grass require a very different colouring from the half -grown insect which leaps actively about in the open ; the colour therefore changes at each moult, adapting the insect to its increased activities and gradually giving place to the colour scheme of Surface Grasshoppei', 46 FORM AND COtOUR. the imago, wliicli usually eoinmencos to apj)eav in the last moult but one or two. There are countless instances of these changes and we may constantly see instances of cryptic colouring-. On the other hand, we find some insects very vividly and brightly coloured, so that they stand out strongly against their surroundings. Fia. G3. The South American Caterpillar ivhich suggested " warning colouration ''; tJie light bunds are bright gellow, the feet and process red. These insects are usually distasteful to birds and predaceous insects either from their taste, odour, or the oils they excrete. Their striking colouration is accordingly supposed to be " warning ", i.e., warns the birds that the insect is unpleasant. A young bird eating such an insect associates the bright colours with the unpleasant taste ; it then refuses to eat similarly coloured insects and warningly coloured insects escape. There are many insects supposed to be warningly coloured ; red, orange or yellow with black are common warning colours. Most bees and wasps, ladybird beetles, some blister beetles, and some butterflies are so coloured. Fio. 64. Moth of the precious Caterpillar, coloured cryptically in grey and hlacl. WARNING COLOUR. 4t Dragon flies are often brilliant, Avith red, bhie, yellow, green and other vivid colonrs associated with black. A few grasshoppers are very vivid. Warning colouring is very common. It is found that many insects exactly copy the markings of such warniiigly coloured insects ; the former Fig. 65. Warningly coloured Beetle. are not distasteful, have no unpleasant taste or smell, but escape because they look like nasty butterflies or beetles. This is known as Batedaii mimicnjy after its discoverer. Many Danaid butterflies A \\ "'--^ Fig, 66. Fig. 67. A Wasp, protected hy its stiny and A Fly, harmless and edihle, lohtch xmrningly coloured. mimics the Jl^asj). are Avarningly coloured; other butterflies, not of this group, but living in the same locality, exactly mimic the Danaid in form and colour ; they look closely alike and only careful examination shows that 48 POEM AND COLOUt;. the latter are different in fundamental structure. The edible mimic escapes through its resemblance to a distasteful insect. This form of mimicry is common. Edible butterflies mimic nasty ones ; moths mimic butterflies ; flies mimic moths ; flies also mimic bees or wasps ; there are abundant instances which can be cited among- Indian insects (figs. 6G-68). Another form of mimicry occurs when we find in one locality a large number of insects with a general warning scheme of colour, say black and yellow. Among all these insects having a similar colour scheme some are genuinely nasty, protected by unpleasant taste, bad scents, poisonous bite, sting, etc., so that birds will not willingly eat them. Others are not unpleasant, but pretend to be so by " adopting " the same scheme of colouring. This is called Mullerian mimicry and is also common. It must not be thought that an insect can change its colour voluntarily ; the colour of insects is fixed and all of a species are coloured much alike ; but it is believed that in the evolution of insects, the species " adopted ^^ or gradually acquired colour schemes, and so the warningly coloured insects arose first and other species later. If we disbelieve evolution, we may say that the mimics were made like the warningly coloured insects, and any misconception due to the deficiencies of the terms used will be avoided. A few insects are so coloured and formed as to resemble unpleasant substances ; thus the larvae of the citrus butterflies are not unlike the excrement of a bird and feed on the leaves in such an attitude as to assist the resemblance (fig. 195) Fig. 68. A common Fly {lejl) vliich Viimics Ihe common Bee (ru/li) mid so escapes 'its foes. {Magnijled.) Deceptive colouring is very common ; it is apparently designed to deceive birds and is useful when an insect is in flight. The Leaf Butterfly is an instance ; the upper wings are brightly coloured and the insect in DECEPTIVE COLOUH. 49 flight is conspicuous; it flies along and suddenly settles wiili wings Fig. 69, The Hooded Grasshopper, wliicli combines projection due to the hard sharp hood with cryptic and deceptive colonring. folded, exactly resembling a dead leaf ; the suddenness with which the bright colours of the upper surface vanish is extremely deceptive and makes it very difficult to distinguish the butterfly. Grasshoppers have the same colouring, the lower wings being often brilliant and very notice- able when the insect flies ; it then suddenly settles with folded wings and the colours exactly blend with the dry grass ; it is impossible to see where it is and Ave may conjecture that a bird is also deceived. This is a common scheme of colour and is usuallj^ shown l)y the upper wings being' cryptic, the lower verj^ bright and conspicuous. Moths, grasshoppers and other cryptically coloured insects are the best instances. Many butterflies have beautiful, diverse colour- ing, which does not fall into any of the above schemes. Some have very conspicuous marks on the hind angle of the wings or on the front wings; these are sup- posed to mislead a bird which attempts to seize them, the bird snatch- ing at the conspicuous y\g. 70. spot on the wing and so a Butterfy ->nth eye spots to deceive birds. 50 FOllM AND COLOUn. missing the l)utterfly which loses a part of its wing* but escapes alive. This may seem to be a fantastic explanation, but it is borne out by good evidence. Other butterflies are perhaps coloured in rough imitation of their surroundings as seen from above, i.e., their colouring blends with the light and shade of vegetation when they are looked at from above as a bird looks at them. We cannot be certain of this since we see them from about their own level, but the explanation of the colouring of many butterflies is probably to be found in this. A few insects have apparently a scheme of colouring that is meant to terrify an enemy or frighten it away. Such are the Hawk Moth Caterpillars, which when alarmed sud- denly expose large eye-like spots and look like a ferocious snake ; others simply look bizarre and fearful, if we can judge from what we imagine a bird feels when he encounters one. Many caterpillars have such devices, coloured spots and stripes, brightly coloured filaments, waving hair tassels and the like. These are the principal colour schemes found in insects, but still we are io-norant of the significance or value of the colouring of many insects. Ground beetles are commonly black or very dark coloured, perhaps because they live in hiding. Many are white, especially those which come out in the dusk, and this may facilitate courtship and mating. Colouring is possibly not determined by utility in every case, but is simply for beauty, and the general effect of insect colouring is, from man's point of view, chiefly one of beauty. Possibly this is the case also from the insect's point of view, and though necessity is considered, the whole scheme may be primarily for beauty. Fig. 71. Lacewinc) Bugs ; their minute size is shown ly the hair line. i^No meaning except fure leaiitg can he assigned to their delicate ornamentation.) COLOUK SCHEMES, 51 We may remember tliat llie colour schemes of tlie very great majority of insects have to us no meaning*. The few tliat exhibit Batesian or ]\Iullerian mimicry or are warningly coloured, arc a very small part even of known insects. The ordinary insect picked up at haphazard does not fall into any class ; we can see sometimes that the colouring perhaps blends in several scliemes, cryptic, warning, sexual and the like ; but avc cannot judge in tlie least of the real value or significance of the colour schemes of nine-tenths of the known insects. It would not be surprising* if a growing* knowledge produced a far profounder and truer interpreta- tion of colour in insects, more in accordance with tlie real needs and necessities of insect life. pid CHAPTER IV. Fig, 12. Ortho'pterous Insect, CLASSIFICATION AND NOMENCLATURE. AVERY laro-e number of insects are known to occiir in India as in other tropical countries which it is no easy matter to classify. Insects are primarily divided into nine orders, two of which are of little import- ance and rarely met with. The seven larg-e orders are easily distinguished B.ccording' to the structure of the wings and mouth- parts and by the life his- tory, A knowledge of classification is necessary to enable one to place every insect into its order ; one then knows whether it may be expected to have a metamorphosis or not, and one has a clue to its probable habits and nearest allies. It is not necessary in these pag-es to go further than the principal orders. The final classification into sub'families, tribes, genera and species is a matter of special study and is best left to those who work in museums and study only the dead insect. The student will require also a knowledge of the chief families of each order, but this point cannot be entered upon here. The seven principal orders are most conveniently known by their scientific names, since there are not in all cases English equivalents. The following are the orders with their distinguishing characters : — Orthopterci {orthos = straight; jo^ ^- 1 HlL^ \ T i N - i f riG. 80. Semipterous Insect. Fig. 79. Dipterous Insect } Larva and Pupa belotv. One pair of wings only. Suctorial mouth-parts. A metamorphosis, the larva being, as a rule, a legless maggot. Ilemiptera (^<^y;^^ = half ; ptera ^ wings). The bugs. The basal half of the upper wings often thickened. Sucking mouth-parts. No metamorphosis. Distinguished from beetles most readily by the fact that the wings do not meet in a straight line, but overlap. OHDMS. 55 Pig. 81. FovHeen-SpoHed Leaf Beetle. a. Larva ; b, Fwpa ; d. Pupa case : c. Imago. All magvified but d. is more difBcult ; young Orthoptera and Bemiptera are of course easily dis- tinguished by the mouth- parts. A caterpillar with not more than five pairs of sucker-feet belongs to Lepidoptera ; if it has more, it is one of the few Jlymenoptera whose larvre resemble caterpil- lars. A larva without snclcer-feet and not hairy is prol)ably Coleopiera if it has a well-marked head, These seven orders are generally easily distinguished ; look first at the wino-s, then at the mouth-parts ; a two-winged insect is probably one of the Biptcra; an insect with four clear, transparent wings belongs to NcuropUra if the wings are large ; to Tlymenoptera if they are small. If the wings are covered with scales, it is a butterfly or moth ; if the upper wings are hard and meet in a straight line, it is a beetle, but if one lies over the other, it is one of the llemipUra. In the latter case a glance at the mouth-parts will confirm it. It is only the exceptions to these rules that make classification difiicult, and as the apparent exceptions are numerous, one cannot expect to place every winged insect into its order by superficial examination. When the insect is young, the case Fig. 82, Lavm. Pupa and Imago of a ffymenopierom Insect. 56 ctASSIFiCATION AND NOMENCLATURE. and Bipiera if it is without any definite head. There are, however, CL Fig. 83. Diplera; Larva on left. Pupa in middle .^1^> • ,r<'. -•sg It' Fig. 84 Slug Moth, a, h. Caterpillar s c, Cocoon; d, Male J c, Female , Imago on right. no means of classify- ing^ larvae accurately except by rearing them. The same is true of pupse. ; but if the pupa is sus- pended from a plant, it is probably that of a butterfly; if it lies in a silky cocoon or in twisted- up leaves, it is probably that of a moth. Should it be in the ground with- out a cocoon, it may emerge as a beetle or a moth. If there be many in a nest together, they belong to Hj/menoptera. The figures of different larvae and pupse will help in classifying them. The following English terms are generally used for the larvae of different groups : — A hop])er is the young (nymph) of a locust or grasshopper. NOMENCLATURE. 57 Fig. 85. Young Leaf Insect. {Compare Figure 49.) studied. lu all, some two to three hundred thousand kinds of insects have been classified. Each of these has received a dis- tinctive name. In the first place, all insects that are almost ex- actly alike, that can breed tog-ether, and that may have been descended from the same pair of insects during" recent generations are said to belong to the same species; species in fact are kinds of insects. A number of species which are similar in all but colouring or other A caterpillar is the larva of a butterfly or moth. A gritb applies to the larvii of Coleoptera or llymenoptera. A maggot is the larva of a fly [JJiptera) . A chrysalis is the pupa of a butterfly or moth only. Nomenclature. Insects have been systemati- cally studied during the last two centuries and only a small part of living insects have been examined. In India a very small part of the insect fauna is known, though some of the very common ones have been Fig. 86. Wood-horing Beetle, a, Gruh ; b, Pujm ; c, Female; A, Male; e, Tunnels in ivood. 5S CLASSinCATlON AlCD NOMENCLATURE. unimportant characters are said to form a genus. Each genus and each species receive names. Thus tlie Indian locusts belong to one genuS; Acridium. Of these one species is Acriduim peregrinum, another is Acridium succinctum, and so on. Each species thus has a double name, one for the species, another for the genus. These names are generally com- posed of Greek or Latin words. In old days every one in Europe knew these languages, and so these names could be understood by scientists of all the Euro- pean nations, whether they were French, German, English, etc. Originally these names had definite meanings, but the number of known species is now so great that almost any word is used put into a Latinised form. At the end of every scientific name there is an abbreviation for the name of the person who first described and named that insect ; thus the full title of the North-West locust is Acridium peregnmim, Oliv. ' Verc grinum ' is the name given to the species by Oliver, and as it resembles other insects of the genus Acridium it is put into that genus. Fig. 87. Mulherry free Boring Beetle. Fia. 88. Grnh of Mvlhevry Borinci Bedle. This system of naming insects is absolnloly necessary for syslema- tists and scientists; it is liowever very confusing, as entomologists are not agreed as to the original name given to each insect. Two INSECT NAMES. 59 entomologists may find the same species in different places and both will describe and name it, using- different names. Both names cannot be \ised, and it is now agreed that the name which was first published shall be used. This again causes great confusion, as people cannot ao-ree which was the name first used. It can be seen that the naming o£ insects is a very difficult mat- ter; there are, for instance, some 2,500 species of grasshoppers and locusts described; of these perhaps 400 are known to live in India, but there are probably also in India some 400 more which have not yet been described; it is no easy matter to know, first, if any Indian grasshopper is the same as one of the 400 already described in India; second, whether it is the same as one of the 2,500 described from all parts of the world; or third, whether it is new; if it is new, that is, not yet described, it must be described as a new species and perhaps as a new genus. As locusts and grasshoppers make up only one of over 200 families of insects, it is clear that it is no easy matter to use the scientific names of insects correctly. In this book scientific names are not much used; it is as easy to learn about the Bombay locust as it is about Acridium sicccincitcm, L. Persons who see an insect in the field and know that it is Pentadact^/lortJiopteroi' des vigintioctonigropuncttdomaculata N. are apt to forget whether it is a grasshopper or a beetle and whether it is injurious or not. No good is done by hurling scientific names at an insect in the field. It is far more important to bo able to recognise a cockchafer, to know that its grub lives in the ground and eats roots, and to know that, if one is found, others are likely to be there and should Ije destroyed before they lay eggs. As far as possible, plain English names have been used for the Fio. 89. Caterpillar, Pupa and Moth. 60 CLASSinCATION AND KOMENCLATUfet. insects mentioned in this book. To avoid confusion and to assist reference, I have put as a footnote the register numbers of the oflicial collection, the name of the family and what I believe to be the correct designation of the insects referred to in nearly all cases. Part 11. PREVENTIVE AND REMEDIAL MEASURES. CHAPTER V. ORIGIN OF INSECT PESTS. IT is well known that the natural increase of any insect would be very large if the restraining checks were removed. It is also true that a species rarely becomes so abundant as to cause serious damage to crops. We may here shortly discuss the causes which lead to the undue increase of an insect, so that it becomes a pest. In this book we propose to record about one hundred species of herbivorous insects wliich have become injuriously abundant in recent years ; tliis is a small fraction of the herbivorous insects common in the plains, which can and do feed upon crops. Why do not the larger part of these insects also become abundantly destructive ? There is no answer to this question, nor has it ever been answered in any country ; we can but dimly see the laws which govern the increase of animal life, and in this limited space we can but discuss some of the most obvious laws and phenomena which a close study of nature presents to us. In the first place, let us examine the rate of increase of an insect. A single female of one of our commonest moths lays over 500 eggs. Of these actually 200 have been reared to moths again under artificial conditions ; these produce 50,000 eggs, since roughly half are females. Of these again we rear 30,000 moths which produce 5,000,000 eggs. This is the rate of increase based on the actual ratio that live in captivity. We see that the increase of one moth in three generations is vast, equivalent approximately to ten large and devastating swarms of caterpillars. This is not a peculiar case, just one taken at random and well within the limits of any herbivorous insect investigated in India. We can see then that every moth feeding upon a crop plant should, if there were no checks, produce a vast progeny. Clearly also the checks are very efiicient since this does not occur. The checks upon the increase of insects may be roughly said to be climate^ lack of food J enemies. Climatic checks are of great importance, and we cannot pretend yet thoroughly to understand them. Most insects become torpid with cold and hibernate (lie dormant) for some three months. Not only does this stop increase at this time but the hibernating insect is exposed to many dangers during this period — dangers it cannot guard against. Probably a very large percentage do not survive the winter. There is 64 ORIGIN OF INSECT PESTS. then the period o£ dry lieat, which is to many equally a period of rest during wliich their enemies are especially active. Finally^ there are four months of suitable weather, during- which they can increase ; even this is probably not entirely favourable as it is likely that excessively heavy rain and wind storms do much to kill moths and flying insects. The lach of food is another powerful cause ; as a rule, plants grow vigorously during the rains, many grow during the cold weather, after which a great proportion of the vegetation dies down. An insect feeding on a plant that grows only in the rains has but a few months in which to multiply; if it can also feed upon cold weather plants it has some months longer, provided it is not numbed by cold, and finally it has no food for some months of dry heat. The third great check is due to enemies j these include the parasites, the predatory insects, the birds, bats, etc. As soon as an insect becomes abundant, these attack it and reduce its numbers (see page 268). Fungoid and bacterial diseases are also operative in insects as they are in man and domestic animals. In the jungle or forest, we find that, on the whole, these causes acting against the naturally large ratio of increase, tend to preserve an even level for all insects ; what we may call the balance of life is main- tained, and, neglecting small variations, in nature the numbers "bf each species are more or less constant over long periods. Where man has not interfered, insects do not become destructively abundant ; there are excep- tions, of course, but then the balance adjusts itself very swiftly. We are, however, not dealing with the jungle where nature reigns, but with artificially maintained areas of cultivation. There man has upset the original conditions in very definite ways for which he pays the penalty. Firstly, the balance of life is commonly upset by the new forms of life which are introduced by man himself or which come with him. The introduction of the Gipsy Moth to the United States let loose an insect whose increase was so enormous that as much as four lakhs were spent yearly in one State in checking it. The disastrous results that followed the introduction of the Indian mongoose to the West Indies, of the rabbit to Australia, of ferrets, stoats and weasels to New Zealand, of the sparrow to the United States, and of the Indian myna to the Hawaiian Islands are examples of the manner in which the balance of life is upset by the^ intro- duction of new forms. Secondly, we may refer to the interference with the climate caused by the changes made upon the earth's surface by man ; such a change as the destruction of the forests is the most obvious case, leading to profound modifications in the climatic conditions of large areas. THE BALANCE OF LIFE. 65 Thirdly, the plaut life may be entirely altered. This is by far the most obvious cause and deserves separate discussion. Lastly, the interrelations of the fauna are deliberately upset by man in shooting insectivorous birds, in checking' beneficial insects and in making" the conditions unsuitable to useful insect-eating animals. The last two are the really important causes that affect insects directly. In cultivated areas, we grow large numbers of the same plant side by side; any insect that can feed upon a cultivated crop finds abundant food, has not to search for it, and can readily lay its eggs in one place. Instead of searching through the jungle for the particular plant she requires, a female moth emerges in a field of that plant, finds a mate at once and can readily lay eggs ; she is not exposed to enemies in her flights to find a mate or in her endeavours to find sufiicient food-plants on which to lay her eggs. Not only does man grow larger areas, but he grows the plants at seasons of the year when food is otherwise scarce ; the crops grown under irrigation in the hot dry weather help many insects over a critical time and so give them an additional opportunity of breeding and multiplying. Further, plants grown under somewhat artificial conditions have not the same vigour to resist pests as plants growing wild in the jungle. Few crop' plants are grown where they naturally thrive ; in the jungle there is competition, there is a struggle for life and only strong healthy plants in good vigour can live ; in cultivation plants are kept alive by stimulation, are grown in soil that does not suit them, are " domesticated " and have not the vigour that especially resists the plant parasites. How seldom we see a wild plant attacked by scale insects or plant lice? A wild plant has the vigour to resist, to make itself distasteful and to out arrow the disease. In addition to helping the increase of insects by the artificial manner in which he grows his crops, man does so also by checking the birds and other predators which check insects. These include birds, lizards, bats, predatory and parasitic insects and the like. They are discussed in detail elsewhere, but we can see that our artificial conditions upset this part of the balance of life and so give opportunities for the abnormal increase of insects. If we consider this question as a whole, we can dimly see that every now and then the checks which are usually operative may temporarily be suspended, so that we get a vast increase in the numbers of some common insect, i.e., of an insect which, if abundant, probably destroys a crop. Then we have an outbreak of a '^pest,'' a perfectly natural phenomenon due to causes which man himself brings about, In nature, and generally 66 ORIGIN OF INSECT PESTS. in our cultivated areas, the increase of insects is automatically and natur- ally checked ; at times it is not checked in our artificial surroundings, whereby we suffer. These facts require to be borne in mind in considering- our pests and the manner in which they appear. An outbreak of an insect pest is not due to supernatural phenomena, nor is it wholly due to au east wind, last yearns flood, late rains or other causes. Cultivators commonly believe that the sudden appearance of a pest is more or less supernatural, and for that reason not capable of treatment; it is no more supernatural than when a bullock gets into a young crop and eats it, only we can trace the bullock and cannot always trace the insect pest. Above all we must remember that our insect pests are always with us, but not always abundant. Insect j)ests do not appear suddenly from nothing ; they are the insects common throughout the plains, which under a certain combination of circumstances increase sufficiently to do damage. No conditions of manuring, irrigation or the like can produce them, but suitable conditions can enable them to increase beyond their natural limits and turn them into a pest. As can readily be seen, the conditions which govern this very delicate balance of life are extremely complex, and we cannot always see what causes have led to a particular result. The preventive measures discussed in the next section, as well as one simple method of encouraging parasites (see page 271), ai'e based upon our knowledge of these causes. A little consideration further helps us in some cases to anticipate an outbreak of an injurious insect, on perfectly simple reasoning. An entomologist who sees hundreds of the moths figured on page 188 flying in March, as is commonly the ease, will know that, if sufficient wild plants are not available, the crops will be attacked ; he will also know that there must have been abundance of the caterpillars of this moth before the cold weather, and that probably they might then have been destroyed either in the crops or by more careful attention to clearing away weeds on waste strips and headlands. Again, if we see a swarm of caterpillars in the fields or in uncultivated land, it is worth while ascertaining whether they are extensively attacked by parasites or not ; if we see many flies (fig. 325) or ichneumons (fig. 323) among these caterpillars or laying eggs on them (a matter requiring but little observation), it is probably advisable not to destroy these caterpillars unless they are doing very great injury ; if, however, we find no parasites or only small numbers, we must use every endeavour to destroy them or prevent them becoming pupae, as the next outbreak will be a very large one, An agriculturist who understands something about these moths ARTIFICIAL USB OF CHECKS. 67 will see ways in which he can turn his knowledg-e to good use either in preventing the occurrence of such pests or in checking them. A subject that has unfortunately attracted general attention is the fascinating one of using one insect to destroy another. "We know that there are parasites, predators and the like which destroy insect life ; the inference is that we should be able to check all our pests by their means. Entomologists have devoted great attention to this point, with an almost complete record of failure. In one instance, under very peculiar condi- tions, success was attained, a ladybird beetle being introduced to destroy a virulent insect pest. The particular conditions in this case were that the pest was newlij introduced, had no enemies in the locality to which it was introduced, and could be traced to the country whence it came. It was not difficult to obtain from that country the beetle that there preyed on it, and liberate it where it could find its accustomed prey, which was the only insect it recognised ; it utterly destroyed the pest, partly because it had no other food and partly because it had no enemies in that place. Evidently this could be repeated with some chance of success, but only in the case of newly introduced pests. Our pests in India are probably of long standing ; they have enemies here, but the fluctuations in the balance of life occasionally enable them to be destructive. No parasite, no enemy will entirely destroy an insect that is established throughout India, and there is no advantage to be gained by introducing fresh parasites. There is also no ground for believing that in the near future we shall be able to artificially employ fungoid and bacterial diseases in the destruction of insect pests ; they appear to require special climatic conditions {e.g., very moist heat), and this places the matter beyond our control. What is of extreme practical importance is to encourage, not particular parasites that are already doing their utmost under conditions beyond our control, but birds which will destroy any insect that becomes too numerous. Birds are the fluctuating check on insect life, the safety valve as it were ; they congregate where they lind insects, regardless of their species or habits, and constantly consume the superfluous and superabundant insect life. We can encourage birds by planting trees, by letting them take a not too excessive toll from the fields ; and every' insectivorous kind means a large diminution in our pests. We cannot as yet equally encourage other beneficial organisms, but must rely on our own efforts to check the superabundant insect life that destroys oui' crops. CHAPTER VI. PREVENTIVE AND REMEDIAL MEASURES. PREVENTION is better than cure, costs less to carry out and forestalls the loss of crop. Most measures of this kind depend upon a kind of commonsense that is practically non-existent in India and rare anywhere. It is difficult to prove the value of preventive measures, which depend solely upon a thorough knowledge of the conditions under which insects live or upon reiterated experience. If our pests come regularly and at definite times, the value of such measures can be clearly demonstrated ; but since insects are not so accommodating and come at haphazard, it is difficult to bring them within range of actual experiment. There are several simple precautions which are sufficiently obvious to any one who practises agricultm-e intelligently ; they are also general in their appli- cation and should form part of every agriculturist's stock of maxims. Clean culture is important ; many insects breed on common weeds, become abundant and are driven by lack of food to attack crops. That is a common way in which many insects become pests. An herbivorous insect that increases beyond natural limits will attack a crop on which it can feed, and it is folly to encourage pests by growing their wild food- plants within reach of cultivation. Weeds are always a source of danger and do no good. This applies equally to the strips of grass that border on fields, to waste lands, jungle, etc. Good grass is safe and brings no pests ; mixed weeds and low vegetation should be replaced by grass or kept down. The ideal cultivator allows no weeds or plants to grow other than crops and grass. Another precaution consists in removing crop plants when the crop is harvested. Old cotton plants afford food to cotton pests, thus helping them through critical seasons when food is scarce. Juari stubble har- bours the moth-borer and enables it to hibernate. A crop plant that has yielded should be removed and not allowed to breed pests after it is useless. It is at all times necessary to weed out dead and dying plants from a crop and burn them. The brinjal grower pulls out the plants attacked by stem-borer and leaves them in the field. If he burnt them, he would destroy his pest and check its increase ; as it is the calerpillar completes its metamorphosis, comes out as a moth, lays its hundred eggs and the loss of plants steadily increases. The same thing applies to all refuse plants, dead wood, rotting fruit, etc. Even weeds should be removed when they are pulled up and not allowed to rot in the field. No vegetable matter should ever be allowed to decay in a field or anywhere MIXED CROPS. 69 but in a proper compost heap. The useless cotton bolls not worth pick- ing breed cotton pests and do much harm; they should be removed periodically and carefully burnt with all their inhabitants. He who leaves fallen mangoes to rot where they fall should not be surprised if his sound mangoes are attacked by pests bred in the fallen ones. Rotation of crops is a practice of some value and is more valuable the larger the area rotated. Keeping two acres side by side in sorghum and cotton alternately does not help matters so far as insects are con- cerned ; but the rotation of large blocks of land in alternate crops does much to check pests. In rare cases it is possible to check a pest by not growing its food-plant for a year or longer, substituting other crops. The practice of growing mixed crops has a profound influence upon insect life and is generally most beneficial. Growing crops in separate blocks which might be mixed and grown in alternate rows is a direct incentive to insect attack, and the mixed cultivation of the Indian culti- vator might well be followed in other countries where pests are rife. Mixed crops approximate to natural conditions and discourage the increase of insect pests. Cotton grown with tur, urd or maize suffers less from insect pests which do not so easily find the cotton j the moth has to search for her food-plants, and in so doing runs risks of enemies ; the caterpillars cannot simply crawl from plant to plant, but must move over the ground with the risk of being snapped up by ground beetles, frogs or birds. The mixed crop is a great safeguard, though the cultivator does not know the reason but benefits by the accumulated experience of distant ages. Opposed to the mixed crop is the small plot of any single crop. A small area of a single crop in a large area of other crops is an inducement to insects to cluster in that small plot, and destroy it. Insects which are harmless when scattered over one thousand acres are extremely destructive in a small plot, and probably devour it all. Nothing is more fatal than to grow a small area of a plant j it is not the small plot but the relative area which matters ; if a crop is grown in its due pro- portion, say one thousand acres in five thousand, it may be broken up into small plots, but the insects are scattered over the district ; but if there is only one plot of say ten acres in that five thousand acres, then that plot is liable to suffer. Many promising experimental cultivations of crops suffer because insects gather in that one little plot. If the experiment had been on a larger scale or if the pests had been checked, the experiment would have had a better chance of giving true results. If one grows plants under such conditions, one must expect abnormal results and take measures accordingly. Much encouragement is given to pests by the promiscuous growth of plants that harbour pests at seasons when the crops are not available* 70 tllEVENTIVE Aisri) REAtEDlA-L MEASUllfiS. Bhindi is a plant that should be rigidly excluded from cotton areas, as should hibiscus, the roselle hemp [ambadi, skerria, etc.), the holly-hock and a few other malvaeeous plants. If grown they should be grown only where cotton is also growing so as to draw off the pests from it. There is probably a large field for the prevention of pests in this way, but we have not yet obtained the requisite knowledge of Indian insects to be able to make use of it. Equally we do not yet know how to use trap crops to the best advantage. Trap crops are crops grown to lead the pests off from the valuable crop plants. The cultivator who sows mixed seeds in an irrigated plot of land and pulls out half of the plants with caterpillars on has unconsciously used a trap crop and saved his really valuable plants. If he went one step further and destroyed those caterpillars and plants he Avould do still more good and use his trap crop intelligently. There are two ways in which trap crops can be used ; we can sow an early small crop for the insects to eat, sowing the bulk of the field later and destroying the early crop with the insects on or leaving' it until the main crop is well established ; we can sow two crops together, one a valueless crop to act as a bait for insects and which grows only so long as it serves its purposes, being destroyed as soon as it is full of pests or as soon as it interferes with the growth of the main crop. Neither method has been adequately tried in India, though the latter is unconsciously done by cultivators, and in rare cases deliberately; the method deserves to be far more widely tried on an experimental scale. The most valuable of our preventive measures after mixed crops is the practice of killing whatever caterpillars are found in crops, when they are few. If cultivators realise that caterpillars are not harmless and that anything that eats his crop may become a serious pest, and if he would but kill these stray insects from the first, the/ would not multiply to the extent that they now do. At present the first brood of insects is never killed, the second is larger and does more harm ; the third eats the whole crop or perhaps emerging next season after hibernation wipes out the young crops. If the first brood were checked, there would be no second or third brood and no loss to the crop. Such a procedure is far more possible in India than in other countries ; the process of picking off caterpillars is one that is not essentially different from the process of laborious hand-weeding and can often be done at the same time^ It is as natural and feasible as weeding, only it has never become part of established usage. Caterpillars are always safe things to kill, though other insects are not, and it is from caterpillars that most of the harm to agriculture comes. A common practice which helps crop pests is that of letting stray crop plants grow either at the wrong season or in the wrong field. Stray liEMEDltiS. 1 1 plants of maize, ot bliindi, of juari, of beans, of any erop plants should never be g-rown in the fields at any time. They eome up from stray seed and are allowed to grow freely, perhaps in border strips ; they harbour pests and help them over critical periods when food is scarce ; all such plants should be pulled up unless grown for a distinct purpose. A precaution that might be used far more freely is that of trenching, either to isolate an infested plot or to protect an uninfested one from a neighbouring infested one. When caterpillars are abundant, they eat the plant they are on and move away to others ; rarely they move in a body, usually singly ; the owner of an infested plot is doubtless glad to see them go, but his neighbours should certainly make trenches, which need not be more than a few inches deep with sloping sides. Such trenches do much to isolate pests which cannot fly, especially caterpillar plagues ; these caterpillars often become restless and move about at a special period of the day, falling very soon into the trenches ; large numbers can then be killed in a very simple manner. Another simple precaution on small holdings is the common hen, an indefatigable insect hunter ; turkeys and guinea-fowls are equally good but rare. The hen should be a regular part of a ryot's small belongings, and there is a certain justice in obtaining fat hens from the insects which eat crops ; it is necessary to give the hen a basis of other food and not compel her to a purely insect diet. Whilst there are many methods of destroying insect life on a small or large scale, for every pest there is, as a rule, one single remedial method which proves successful. There is no one specific capable of universal application, no " cure-all,'''' no patent medicine warranted to kill every thing from fleas to locusts ; if there is, it has not yet come within the range of practical science and is made only to sell and not for use. In devising remedies, the essential things are a knowledge of the habits of the insect and a full understanding of the local conditions. The habits of the insect vary little from place to place, and their variation can be predicted ; but local circumstances vary from village to village, and what is effective in the west may not suit the east. Thus it is that no remedies can be given for such a pest as the Rice Stem Fly ; its destruc- tion is purely a matter of local knowledge and of so altering the local agricultural practices as to baffle the insect ; no amount of scientific training', no remedies from the most advanced scientific nation can help us in a case like this, and nothing can replace the local knowledge that, combined with a knowledge of the habits of the pest, at once points to the one weak spot in the life of the insect and adjusts the agricultural practices accordingly. That is the essence of remedial measures. n PllEVENTIVE AND REMEDIAL MEASURES. The remedies described below are those so far tested against crop pests in India ; they have been laboriously worked out after many failures and in the face of many difficulties ; they are in the nature of sug'gestions, not of recommendations ; such suggestions as are of value when one is face to face with a pest and seeking for some method that will fit in with the agricultural conditions and with the ways of the insect. It is not to be supposed that any one can read these pages and find a remedy for every and any pest. At best they are suggestions, which are the pick of the methods used abroad and which should be familiar to those who experiment with crops ; when the pest comes, some method may be modified with practice, which will perhaps meet the case and give good results. No remedy is of the slightest use unless done thoroughly and with the full determination to destroy every single insect ; if one could but educate the ryot up to that feeling, there woiJd not be a pest left in densely populated India. The simplest method is to pick the insects off the plants one by one and Idll them. This is tedious, but satisfactory and effective. As stated above, the common hen is perhaps the best agent for the purpose, but it is a remedy far more suited to the ways of India where holdings are small, time is plentiful and patience unending than to other countries. Having secured the insects, there is no difficulty in killing them ; a pot of hot water, a little kerosene floating on a pan of water, two flat stones or a fire are all equally effec- tive. The practice of carefully pick- ing off caterpillars and liberating them at a distance of say one hundred yards from the infested plot is not only ineffective and futile but need- lessly cruel. An improvement on hand-picking is a bag, a basket or a net. The bag is a most valuable instrument, which can be made to suit all circum- stances ; with a width of 12 feet and an opening 3 feet high, it sweeps Fig. 90. The most useful bag, loith crost bamboos joined, to the upright side bamboos, allowing the mouth to be instantly closed. BA(iS. 78 Fig. 91. Bag with two upright bamboos. large stretches of grass land ; made smaller, say ten feet by two feet, it can be run over a rice crop, over wheat, lucerne, mustard, etc. ; smaller still, it is attached to the frame of bamboos and a single man draws it between the rows of crops, along grass strips, in any narrow places. The sim- plest pattern has only two upright bamboos to hold open the sides; a better one has four bamboos, the two cross ones with projecting handles, and this pattern closes up automatically at the end of each sweep. The depth of the bag depends upon its use ; on the ground it may be five to seven feet deep ; but should be shorter for use on crops where has to sweep over the plants and not hang too much. At the end of .each sweep the bag is emptied into a hole in the ground ; where the insects are very active, it is twisted up to crush them and then opened. (See page 288, appen- dix A.) In some cases it is desirable to smear the inside of the bag with kerosene oil, heavy oil or tar to catch the insects as they fly in ; a bag which is slightly moistened with kero- sene is more effective because the kerosene at once kills many insects. Fia. 'J-2. tSinall bag with two cross bamboos. 74 PfeHVIiNTlVE AND REMEDIAL MEASUkES. The basket is au adjunct to hand-picking when it is possible to shake insects off tlie plants into the baskets and then into a tin of kerosene and water, as recommended for the Red Cotton Bug (page 104). It is useful for weevils and plant-feeding beetles. The net takes the place of the bag in some cases, as when catching the Banded Blister Beetle. What is required is a bag of cloth cut as figured (page 289) and sewn up, fastened to a slij) of bamboo that is lashed to a short handle. The component parts are very simple, the net easily made and it does good service in gardens and small holdings where such insects abound. The practice of trenching has been mentioned above ; it is useful when one is catching caterpillars with bags as many escape the bag, wander about the soil and fall into the trench, where they can be killed. Baits of cut vegetation are useful traps. Many injurious insects hide during part of the day and will do so in bunches of green vegetation, if these are laid about the field. The bvmches must be examined periodically and the assembled insects shaken off into hot water or kerosene and water. Lights are useful traps for a few insects, especially for such as fly at night. Their use is very limited and fires are often as useful. The light trap consists of an ordinary kerosene lamp hung- over a broad tray contain- ing jaggery and water or water with a film of kerosene. Two bent pieces of tin serve as reflectors. Cockchafers, some moths, ants and a few other insects are generally captured and the trap has a value in certain specific cases. Smoke is a deterrent to some insects, notably such as attack rice and other dense crops in which smoke hangs well. The smoke of a few fires will not kill anything, but may drive out such an insect as the Rice Bug at a critical moment when the grain is forming. The same apphes to cockchafers, wliich attack grain crops just as they are ripening and which have to be kept off until they die naturally or until the grain is hard enough to resist them. Cultivation in the form of hoeing, surface ploughing, etc., is valuable chiefly in exposing insects to birds or weather and is less a remedial measure than a preventive of attack ; many insects that eat crops harbour in the soil or descend there to pupate ; when this is the case cultivation turns out many to become the food of mynas. Other simple remedies are discussed above under " Preventives." A great deal can often be done to check a pest by sacrificing a portion of the crops that is first infested or by sacrificing a young crop with the insects on, in the hope that a second crop will grow up free of the insects. A caterpillar-infested crop can often be wisely fed off to cattle or cut down, when a new crop is likely to come up. T CHAPTER VII. INSECTICIDES AND SPRAYING. HE essence of remedial measures is to attack the insect directly, to make life unbearable to him, to do something to kill him or to drive him away. Such methods are but little known in India ; the methods of killing- insects on a larg-e scale, of poisoning acres of crops, of putting machinery on to deal wholesale destruction, do not occur in Indian agriculture. At most, simple methods aimed at frightening the insects are adopted without any co-operation. With the cultivator's knowledge of the medicinal value of plants, it is somewhat strange that plants are not used as insecticides to a greater extent. The juice of some plants is poisonous to insects, as is the infusion of the dried leaves and roots or the smoke made by slowly burning the dried plant. But such plants are little used ; the juice of Euphorbia neriifolia is used to smear toddy-palms in Gujarat ; the leaves of iiim are believed to keep off insects ; the infusion of Adhatoda vasica or of Calotropis is used in irrigation Avater, as are such substances as castor cake and khurasani. Dekamali gum, asafcetida and similar drugs enter into the composition of such mixtures as " Gondal Fluid.''' These are examples of the use of plants, but they rest on no basis but that of tradition and are not always effective. It is singular that the value of tobacco infusion does not appear to be more widely known ; this is one of the few plants used as an insecticide in Europe, with hellebore {Veratrum album) , pyrethrum {Fyrethrum cinerariafolium) , quassia [Picrana excelsa). From the use of these plants, European methods of checking insects have developed more in the direction of mineral poisons, a branch of entomology never practised in India. At the present time far more reliance is placed on mineral poisons than on vegetable poisons, and even the Kentish hop-grower is abandoning quassia for soft soap. This is true also of America, where the use of purely mechanical methods of checking insects is also being developed to a high pitch. It has yet to be shown how far "Western methods are applicable in the East. To the Western mind it is far simpler to poison the plant by spraying on lead arseniate than it is laboriously to pick off the individual caterpillars. The Eastern mind has not yet fully grasped the idea that insects could be or should be killed by hand-picking, far less by such a method as poisoning the plant with 76 INSECTICIDES AND SPRAYING. arsenic. If there is any value in the use of insecticides in India, their general adoption will be a matter of slow growth that must first be worked out on the experiment farms. Insecticides are insect poisons and act in two ways. There are those poisons which are placed upon the food of the insect and Avhich act upon its stomach, just as medicines and poison do upon human beings. These are called stomach poisons and are meant only for internal application. Fig. 93, Sand S;prayer. If caterpillars are destroying the leaves of a valuable plant and we can put poison on these leaves, the caterpillar eats the poison with the leaves and dies. It is only necessary to put such poison on the leaves of crops, and they are safe from all caterpillars, grasshoppers and other insects which eat the leaves. There are also many insects which do not eat the leaf, but which suck out the juice ; these feed upon the sap of the plant, not on the leaf, and any poison on the leaf never reaches their stomachs. For these we cannot use a stomach poison as we cannot poison the sap of the plant. In such cases we must use poisons which kill when the insects are wetted with them. These poisons are known as contact poisons, since they work only when in contact with the skin of the insect. If a colony of plant lice is sucking the juice of a cotton-plant, we cannot poison the juice, so we throw contact poison on the insects ; all are ^killed, and if the contact poison is properly made the plant is uninjured. Both kinds of poisons have their uses ; we can poison any insect, even a locust^ with contact poison if we use it strong enough, but it is better always to use a stomach poison for a biting insect, such as a locust ; whereas for sucking insects we can never use a stomach poison and must always use a SPRAYING MACHINES. 77 contact poison. Stomach poisons are in general far cheaper ; contact poisons for large insects require to be very strong and may injure the plants ; stomach poisons should always be used if possible, but if they cannot and no other method is available, we must use a contact poison. In using insecticides we must have a method of putting them quickly over a large surface of plant or insect. The value of insecticides lies principally in the rapidity with which they can be applied to a large area of crop. Insecticides can be applied in liquid form with water or as powder mixed with lime, dust, flour, etc. An insecticide applied as powder requires only to be dusted on from a bag and this is the simplest method of application. A liquid insecticide must be applied as a fine spray or mist that wets evenly and distributes the liquid properly over the whole plant. For this work the spraying machine must be used. Spraying machines are of many kinds, all designed to fulfil the one purpose of distributing fluid in a finely divided form over a large area of plant. The simplest pattern is the tin hand sprayer (figs. 93-94). It consists of a pump, which forces air out of a fine nozzle ; the compressed air passes over the opening of a vertical tube, and sucks up a small quantity Hand Sprayer Fig. 94 details of construction. of the insecticide in the reservoir, throwing it out in an extremely fine condition in the jet of air. The whole machine is made of tin and 78 INSECTICIDES AND SPRAyiNG. wood, costing" under two rupees to prepare. It covers very little ""round, however, and is suitable only for gardens and small holdings. It is especially useful for applying contact poisons to small colonies of plant lice, mealy bugs and other sucking insects. With it one can rapidly and effectively kill such insects when they are few. It is not adapted to larger areas, but as a check on incipient diseases it is invaluable and admirably suited to the ryot. If this were in general use, the plant lice that ravage cotton, wheat, mustard and other staple crops could be nipped at the start and never get a real hold on the crop. For more extensive spraying, a larger machine must be emploj'ed, and the Success Knapsack Machine ^ is a useful pattern obtainable in India at a cost of Rs. 46. This machine holds four gallons of insecticide and can be worked on the ground for sj^raying fruit trees or on the back for spraying crops. The insecticide is pumped through the rubber hose out at the nozzle which breaks it up into a fine mist. Either of two nozzles can be used, and of the two the Bordeaux has the most general application and value. The machine is built of copper and brass, which are not destroyed by insecticides. It requires to be kept clean and will last for years with the occasional renewal of the rubber tube. With this machine from one to two acres of crop can be sprayed in one day, using two men at the machine and others to bring water, mix insecticides, etc. This refers to cases where continuous spraying is required as when a whole crop is to be sprayed with lead arseniate. Where individual plants here and there are to be sprayed, as when afliis is attacking cotton, a far larger area can be covered^daily. Larger machines are used to apply insecticides to fruit trees, to special crops and, in Europe and America, to field crops. It is unnecessary to discuss these at present as they are not likely to be used for field crops in India. ' English copies of descriptive Jp^flet are available. Fio. 95. Success Knapsack Sprayer. LEAD ABSENTATE. 79 They can be obtained on wheels to work by hand, on carts to work by £?asolene en.^ines, or portable outfits on the plan of a fire-engine are pre- pared which work by steam and cover a large area daily. The choice of insecticides for each case is a matter requiring care. The principal insecticides are shortly described with their uses. The formulae for prepar- ing these mixtures are given in Appendix A, page 283. Lead Arseniate. This is practically the only useful stomach poison available in India, and no other is required. Lead arseniate is a form of arsenic which combines the best qualities of the older stomach poisons, London Purple, Paris Green, etc., with qualities peculiar to itself. It is a white svibstance, procurable in powder or paste, which is insoluble in water, harmless to plants, and easy of application in the form of liquid or powder. It has a considerable power of resisting rain and so remaining on the plant in wet weather, and its white colour shows up on the plants to which it is applied. It is poisonous to cattle and human beings if taken in any but a very small dose, but it can be applied at such strength as to render plants poisonous to insects though not to cattle. Sprayed on to plants at the rate of one pound in 60 to 100 gallons of water, it is effective as a poison to insects, and its efficacy is increased by adding jaggery, gur or molasses and lime. The usual mixture is one pound of arseniate, three pounds of lime and six pounds or less of any form of low grade sugar or molasses with the necessary water. It can be used at double this strength with M\ safety to plants. Applied as a powder, it is best mixed with twenty parts of wood ashes, road dust, cheap flour, powdered lime, or any other cheap neutral powder : it can then be placed in rough cloth bags and shaken over the plants, Fig. 96. Success Sprayer used on the ffround for spray inff trees. 80 INSECTICIDES AND SPRAYING. It is applicable against all forms of biting insects ; it kills cater- pillars, locusts, leaf-eating beetles, and other insects wbich eat leaves. For an average crop of cotton, young juari or maize, pulse, castor, wheat, Fig. 97. Success Kiiajpsacic MacJiive : lelon-'— left, Bordeavx nozzle ; right, Vermorel nozzle, etc., from 80 to 100 gallons of mixture are required per acre using from 1 to 1^ lbs. of lead arseniate. This explains its small poison- ous effect on cattle, since there is so little arseniate actually on each plant. An insect eats so large a proportion of food compared to its size, that it absorbs relatively much more of the poison and is killed. Experiments made in the Punjab with bullocks fed on fodder dipped in the mixture showed that no harm resulted, and that freshly-sprayed fodder^ could safely be fed to cattle. As a matter of practice, the lead arseniate would not remain on a plant after the lapse of a week or longer, and the crop would have scarcely any poison on it after cutting and harvest- ing. In small gardens, in plots of vegetable crops, it is simply applied KEROSENE EMULSION. 81 by means of tho hand sprayers, and it slionld 1)0 kept for this purpose. On farms, it is useful a.o'ainst many pests wliicli attack valuable crops and render useless the results of other experiments whoso value is shown by comparative yields. Every ex]wrimental farm shovild keep and use lead arseniate, applying it with a good spraying machine and in powder form. It is obtainable from chemists at Re. 1 per lb. in powder or paste form. The paste contains 33 per cent, of water, and 1| lbs. of paste are sold as one pound of lead arseniate and should be used as one pound in mixing with water before spraying. Kerosene Emulsion. The most useful and simple contact poison is kerosene, the ordinary refined kerosene used for burning in lamps. It kills all insects when applied to their bodies, though its action is not fully understood. It acts partly by mechanically closing the respiratory openings on the side of the body, thereby asphyxiating the insects ; possibly it has a directly poisonovis effect on the tissues of the insects when the vapour is absorbed through the system of air tubes which penetrate the body. Applied by itself, kerosene kills the parts of the plants on which it is placed so that the application of undiluted kerosene is as a rule fatal to plants. It has therefore to be applied in a diluted form, and, as it does not mix with water, it is made into an emulsion with soap and water. An emulsion of kerosene consists of water with kerosene in very minute drops ; and on applying such an emulsion, the water evaporates leaving a minute quantity of kerosene on the plant, which is fatal to the insects, but does not injure the plant. The value of kerosene emulsion lies simply in the fact that it can be applied at such strength as to be fatal to many insects and yet not injurious to the tender tissues of the leaf. Kerosene emulsion is prepared by boiling a solution of soap and water, adding kerosene and agitating or beating up the mixture so as to break up the oil into very minute drops, which gives the liquid a creamy white appearance. Such an emulsion can be made very strong and afterwards diluted with cold water to the proper strength for applying to plants. In cold countries, kerosene can be applied to leafless dormant trees in much greater strength than in hot climates. In India a strength of 10 per cent, of kerosene can rarely be exceeded. Kerosene has a peculiar way of " wetting " or penetrating insects which are protected by a covering of mealy white wax. It is therefore particu- larly effective against mealy bugs. It kills aphis (Green-fly), the softer scale insects, green bugs^ small sucking insects and also some of the 82 INSECTICIDES AND SPRAYING. more delicate caterpillars. Its use is strictly limited to these insects and it cannot be used, for instance, to kill large caterpillars which are best dealt with by means of a stomach poison. Kerosene emulsion applied in the ordinary tin hand sprayer, is an excellent remedy for the aphid cb which attack cotton, tuer, beans, pulses and other field crops. In botanic gardens it is useful against all aphis and the majority of the scale insects. In vegetable gardens it can be safely applied against similar pests, and is often usefully applied over the whole of a garden to drive out unwelcome intruders such as crickets, grasshoppers, leaf-eating beetles, plant lice, jumping lice and other insects which are apt to gather in a well watered garden. Crude Oil Emulsion. The heavier petroleum oils have a more permanent and thorough insecticidal effect, especially where the climate is hot and the lighter oils soon evaporate. The ordinary emulsions cannot l)e made with the crude oil, the best emulsions containing crude oil being made by a special process. Such an emulsion, containing 80 per cent, of crude oil, with 20 per cent, of whale oil soap, is prepared and sold, under the name of " Crude Oil Emulsion.^' It was made at the Entomologist^s suggestion, and analysis shows it to be pure, containing the ingredients given above. To use the emulsion, it needs to be mixed with cold water in the proportion of \ pint to a kerosene tin of water (-i gallons). This amount measured and placed in a bucket or tin, is readily mixed with water by pumping water on it from a spraying machine or rubbing up the emulsion by hand. It makes a white milky fluid, remaining fit for use for several days, which needs no further preparation before application. This is the usual strength : it may be made twice as strong, and can then still be used safely on all but very delicate plants. Like kerosene emulsion, this is simply a useful contact poison. It is harmless to all animals if eaten and has a deadly effect on insects only when they are well wetted with it. It should be applied in the form of fine mist by means of a good spraying machine. For all soft insects such as aphis (Green-fly), mealy bug, thrips, green bug, leaf hoppers, small caterpillars, etc., it is effective. One application kills the greater number and a second application completes the operation. In gardens, on fruit trees, on ornamental plants, on vegetables, it is a useful application for these diseases and has a further use in driving off many other insects, Avhich, though not killed by it, find it objectionable. It has a certain value also in houses, which are infested with obnoxious insects, etc, It IIOSIN WASHES. 83 acts simply as a lii^'h class insocticidal soap, witli a loss objectionable smell than carbolic preparations. In this way it is deadly to fleas for instance. It has a further value on domestic animals : kerosene is an excellent application for the skin and there is "no better way of applying- it than in the form of soapy emulsion. For ticks, fleas, and other insects infesting' cattle, horses, dogs, elephants, sheep, etc., this emulsion should be used, at the same time destroying the insects and improving the skin. It is obtainable in five-gallon drums from chemists at Rs. 8-14-0 per drum. Rosin Washes. Rosin has for many years formed the principal ingredient of many excellent washes for sucking insects. When boiled in water with a suitable chemical, rosin dissolves, forming a clear brown wash which can bo safely applied to plants at a strength sufficient to kill many insects. It is used in this way against many of the most resistant scale insects. A rosin wash of this kind on drying forms a varnish, which asphyxiates some insects by closing the stigmata on the sides of the body through which they obtain air. It needs to be applied as a fine mist, by means of a good spraying machine, and then has a considerable wetting power, covering the insects with a film of liquid which on drying kills them. There are a variety of formulae for preparing this wash. Two may be taken as being the simplest and best, both having been tested in India and found fully effective. (See Appendix A, page 284.) These washes are similar in effect and use. The second contains fish oil soap as well as rosin and is a more powerful wash in consequence. As caustic soda and fish oil are less easy to obtain than washing soda, the first wash should generally be used. Only when large quantities are to be prepared is it advisable to use the second wash. The rosin used must be the clear brown fir tree rosin imported from Europe. This rosin may also be obtained from the Forest Department at Dehra Dun and Naini Tal. The washes cost about Rs. 3 per 100 gallons, or Rs. 4 per 100 gallons on estates far from the coast and a railway station. These washes are for use against scale insects such as brown bug, green bug, black bug, etc., also against green fly (aphis) and similar small sucking insects. They have not the wetting power of kerosene emulsion and so are less effective against mealy bug or other mealy insects. They are excellent contact poisons, useful against a variety of pests. Diluted wash (1 lb. of rosin to 10 gallons of water) is also •valuable with lead arseniate, used as a stomach poison, since it protects the 84) INSECTICIDES AND SPRAYING. latter from rain and liolps it to remain on tlio plant. The wash lias of itself no poisoning- effect on eattle or other animals, and may be safely- applied at all times. It has also no effect as a stomach poison against cater- pillars, etc., and is intended simply as an efficient contact poison against all small sncking- insects except the mealy ones. Tobacco. Fermented tobacco forms a decoction which acts as a mild stomach poison and also as a contact poison. It requires to be soaked in water to extract the alkaloids and then is best nsed with the addition of soap. It is a weak insecticide, valuable against plant lice, mealy bugs, soft sucking insects and very small caterpillars, but not so effective as any of the above mixtures. It is obtainable in many parts of India, and the wash is best prepared from the stalks and refuse of the leaf tobacco. Sanitary fluid. The liquids called by this general name consist largely of creosote oil containing carbolic acid (phenyl). Mixed with water they emulsify, owing to the presence of rosin soap, and in weak emulsion are excellent contact poisons. This is an insecticide not in general use elsewhere but which has given excellent results in India. A strength of one in one hundred of water is excellent against all forms of soft sucking insects, against plant lice, mealy bug, green bug, etc. At a strength of one in sixty of water, it is a powerful insecticide, which kills all but the most resistant sucking insects and has a considerable effect on cater- pillars, small grasshoppers, etc. At greater strength it burns the foliage of actively growing plants ; it was used at one in forty against the Bombay locust, killing a large percentage, and at one in twenty killing everyone sprayed, without injury to the hardy foliage of forest trees. Other contact poisons. Countless mixtures have been used as contact poisons since these were first tested and a great variety are still in use. In India only what are known in Europe as "summer washes" can be used, which restricts the available number. There is sufficient latitude in the above mixtm'es to suit every case and no good will be done by discussing the hundreds of mixtures recommended. This applies also to the patent insecticides ; none are yet proved to be as good as the insecticides made on the spot and none have the combined efficiency and usefulness of crude INSBCTICIDES. 85 oil emulsion. Any one requiring a made-up contact poison will find this suitable ; other made-up contact poisons can be purchased ; McDougaFs insecticide is an example, which acts solely as a contact poison. It is valuable as a ready-made and effective contact poison, which acts with much the same effect at the same strength as crude oil emulsion, the latter being far cheaper. Both have been thoroughly tested and both can be recommended. Insecticides are not like patent medicines, requiring only to be applied (or taken), when they do the rest. They must be used in good time ; an acre of mustard that was badly infested with aphis required two hun- dred and fifty gallons of insecticide to kill every aphis, or three times the amount required to destroy the same aphis at the beginning of the attack on another acre. They must also be applied intelligently and vigorously, with the express object of destroying the insect and not because it is the right thing to do. They must be applied properly, with an under- standing of what they are meant for and will effect. Part III. INSECTS INJURIOUS TO CROPS, CHAPTER VIII. PESTS OF THE COTTON PLANT. THE cotton plant suffers from a number of insect pests which lessen the vigour of the plant and diminish the actual yield of the lint and seed. These pests are widespread in India, do a great aggregate amount of damage and largely reduce the yield of probably every acre in India ; but they are disregarded by the cultivator, who is not aware that he can, by adopting simple measures, obtain a larger yield of finer cotton. These pests include the boll-worms, of which there are three species, two identical in almost all but name and one distinct species ; the two beetles that attack the stem ; two bugs that attack the bdlls ; and two caterpillars, an aphis and a leaf-hopper, that attack the leaves. There are in addition a variety of minor pests which are not exclusively pests of cotton and which appear only casually. The Spotted BolUworm. Caterpillars which destroy ripening bolls of the cotton plant and which may be found by looking for such injured bolls before the cotton ripens. They are easy to recognise and readily reared to the imag'o. The life history is typical of the moths. The term boll-worm is in America applied to the caterpillar described in this book as the Gram Caterpillar (see page 144) . In India this insect does not attack cotton, its place being* taken by the two spotted boll-worms /*^.* ■ , and the pink boll- worm, the latter being Boll containing Boll-worm. t i i discussed separately. Life History. — Eggs are laid by the moth singly on the bracts, bolls and terminal leaves of the cotton-plant. Each o.^^^ is small, not more Figures. "Where a fifture is saiil to be magnified, and a hair line is found beside the insect, this line represents tbe iictuanengtli of the insect as drawn. When there is no hair line, the statement, for example " magnified three times," means that each lineal dimension is three times htrger in the figuie, the figures being thus actually nine times magnified if we consider the area it covers. A linear magnification of even three is considerable, and in comparing an insect with a fignre (in the endeavour to identify the insect wilh the figure) a good lens must be used; the human eye cannot compare a small insect with its enlarged figure unless the insect is jiresented to it at least as large as the figure, A lens magnifying ten diameters will be sufficient for every insect figured in this volume, but it is impossible to compare insects and tlie figuifs nnlses a lens is used. Where uo magnification is mentioned and no liair line occurs, the figure is the natural size. x^ £•' I 90 PESTS OF THE COTTON PLANT. than one-fiftieth of an inch across, round, of a bluish colour, finely ribbed and marked. Within a few days it hatches to a tiny dark coloured caterpillar, which feeds first on the bracts and flowers or eats straig-ht into the rind of the boll. In the former case it attacks the bolls within a few days. When no bolls are formed, it tun- nels doAvn the shoots, commencing" at the tip and eating" for a consi- derable distance down the shoot, thus des- Fio. 99. troying it ; normally Spoiled BoU-worm. {3Iagmfiedfoin- times.) it cuts its way through the rind of the boll and the dcA^eloping" lint, until it reaches a seed, which it eats. Having" destroyed one seed it eats another. If the bolls are small, they frequently drop off, but if a larg-e part of the seeds are eaten, the lint is destroyed and the boll filled with excrement. A single caterpillar will rarely destroy more than one large boll but becomes full-fed in the first. More than one is rarely found in a boll unless small ones enter a boll already tenanted by a large one. When the caterpillar is full fed, it leaves the boll and prepares a cocoon of tough grey silk Avithin which it transforms to the pupa. In the black cotton soil of Western India, this is found in the cracks and crevices of the soil. In Cawnpore, Mr. J. M. Hayman states that it is found "on the bolls or bracts, generally between the two,^' and this is the case also iu Beliar and the Punjab. The period of pupation is from 8 to 10 days but may be longer in the cold wea- ther. Eventually the moths come out, I)air and lay eggs, each moth laying about sixty eggs. The shortest total life history occupies about one month. Moths are to be found flying in the dusk; during the day they hide in the ground or on the cotton plants. They are not attracted by light. Both species also feed upon hJiindi [Hibisms eaculent'm), des- Fia. 100. Spotted Boll-toorm. {3Iagnified four times.) gpdTfED BOLL-WOUM. 91 Fig. 101. Cocoon of Spotted Boll-worm. {Magnijied three times.) troying" the fruits or the succulent stems. In Western India these insects are active tbroug-hout the winter, where the temperature does not fall so low as in Northern India. From Aug-ust or September to the following- January or February there is abundance of cotton in which they multiply. In places where the temperature falls, as in the Deccan, Northern India and Behar, they hibernate as pupae, rarely as eggs, larvae or moths, until March. If cotton-plants are left standing in the field or if bhindi is available, they then find food; if not, they remain dormant as moths or possibly pupuj, until the rains. Where cotton is grown throughout the year, it is conti- nually attacked except in the cold weather. Both species are widely distributed in India and practically rang-e throughout the plains. Spotted boll-worms are attacked by three distinct parasites, two ich- neumons and one tachiuid fly. Of these, one ^ is generally distributed and a very important check on the increase of the insect ; the fly ^ has been found in some scattered localities and may be an insect of some importance. Description. — The moth of the com- moner species ^ is coloured with a broad green band extending from the base to the apex of each wing. This green band may be absent, the whole wings being- ochreous or buff. The other species* has the forewings a bright green. In both species the moth measures a little under half an inch in length, the expanded wings nearly one inch. The lower wings are white, and the under ^^^- 103. surface of the body nearly white. "^^^^'^^ Boll- worm Moth. '' J {Magnified three times.) Fia. 102. Spotted Boll-worm Moth. {^Magnified twice.) > 96. Mhogas lefroyi. Ashm. (Chalcida?.) | » 73. Tlarias fabia. Stoll. (Noctuidte.) 2 99. Flectops orbata. VVied. (Tachiaidse.) j * 108, JEarias insulana. Boisd. (Noctuida;.) 9^ pjjsTS OF ^the cotton plant. The caterpillars are short and thick, not more than two-thirds of an inch long- when full grown. The colour is very variable, a mixture of white, g-reen and black, with orange spots. The predominant colour may- be a dull greenish white, with black marks and small orange spots, or black, with an irregular band of greenish white from head to tail with orange spots on the sides. There are tubercles on each segment, bearing hairs ; the orange spots appear only in fairly advanced larvae and the quite young caterpillars are darker. Legs and prolegs are present, the head is dark in colour and there is a dark prothoracic shield. The cocoon is less than half an inch long, oval and flattened, made of grey silk closely woven. It has a resemblance to the grey woolly buds that fall off the cotton-plant. Bemedies. — The treatment of this pest depends upon the conditions under which cotton is g'rown, and the variety of cotton. Certain varieties show a complete or partial immunity to it, but it is uncertain how far any variety will prove immune when grown as a field crop. The varieties now grown as field crops are apparently all attacked. There is only one direct remedy that can at present be advised for general adoption. It is applicable only to cottons which produce a crop of bolls at one time and is ineffective in varieties which continue to produce bolls over a long period. It consists in destroying as many of the caterpillars as possible in the shoots of the cotton or in the first bolls. The first brood of boll-worms is found in the shoots and in the early bolls ; the dead shoots are readily seen and destroyed, the attacked bolls are easily found and burnt. There is no loss of crop, as these boUs will never yield cotton, and it is very important to check the first brood which soon becomes a very large second brood if left alone. This method can be carried to the degree of removing all the early bolls. Another treatment, still in the experimental stage, consists in spraying with lead arseniate when the bolls first form. A preventive measure of some importance is to remove the plants when the crop is picked. It is not uncommon to see stray plants still living in the hot weather after the crop is harvested, which help the pest to increase at a very critical time, especially if showers fall and the cotton makes a littlc growth. The importance of bhindi as an alternative food-plant is also ^ great. "Where bhindi is grown, the insects can breed in it when cotton is not available. Where cotton is a staple crop, bhindi should not be grown except when there is cotton. It should not be grown in Gujarat, for instance, from February to August, as it helps the pest to increase during the hot weather and early rains, providing a large number of PINK ■nOLL-WORM. 93 mollis to In'ood oaf ovpi liars wliicli attack tlio ontton in Auq-nst and Scptomber. Expovlraonts avo in pvno'ress to usn bhindi as a trap crop in or aronnd cotton, in tlio liopo of colU^cting' tlio insects in that crop wliicli can then bo destroyed. The success obtained during' the past season justifies the more extended trial of this measure. The Pink Boll=worm. Associated with the spotted boll-worms is a slender reddish caterpillar found feedino" in the green or ripe bolls. It is easily distin- g'uished from the other caterpillars found on cotton. The moth lays a number of small flat- tened eg-gs, similar to those laid by the majority of small moths ; the eg-gs are deposited sing-ly on leaves, stalks and bolls, and hatch in a few days. The young- cater- pillar is white, with a dark head, and is found feeding on the leaves or on the outside of the boll. It does not immediately attack the boll but bores in through the rind when it has fed for a few days outside. Like the spotted boll-worms this one feeds upon the oily seeds, eating seed after seed until it has become full grown. As a rule one will be found in a boll but exceptionally several attack the same boll. The full grown larva is of a white colour, with bright pink spots, more slender than the spotted boll-worms and without processes. The larval life varies in duration according to the season but occupies two to three weeks in the active period. The full grown larva forms a slight cocoon of silk, in the boll or on the bracts or leaves of the cotton. In unirrigated black cotton soil this may be found in a crack of the dry soil. The shortest period for '74. Gelechia goss ypiella. Sauod. (Tipeidse.) Fig. 104. Phih BoU-ivorm. (Magnified.') 94 PESTS OP THE COTTON PLANT. Fig. 105. Finl~ Boll-ioorm Caferpillar and Cocoon, tJieJormer magnified, the latter natural size. the pupa is from fourteen to eighteen days, after which the moth emerges. The moth is less than half an inch in length, the antennre filiform, the palpi upturned, the gen- eral colour grey brown with dark blotches and suifusions, the wings with long brown fringes. The moth cannot easily be distinguished from other Tineid moths by its appearance alone. Moths fly at night and dusk : they are attracted by light and are readily captured in lamp traps. The pink boll-worms are most abundant when the cotton forms bolls in October or earlier ; the active period is dm-ing the rains and after ; in many parts of India the larvae hibernate in the cold weather, but this is not the case for instance in South Gujarat. In Behar the larvae live through the cold weather in the lint or seed of the cotton, emerging as moths only in March or April ; their further activity depends upon circumstances, the moths laying eggs then if cotton is available. There may be a further period of rest during the dry hot months before the rains. Actually larvae have been found active in all raonths of the year, but there are two main periods of rest, from November to March and from April to June, depending upon climatic conditions and the supply of food. Fig. 106, Pink BoU-irorm Moth. {^Magnified six times.) PINK BOLL-WORM. 95 The pest is apparently universal in India, Ceylon, Burma and the Straits Settlements, causino* a very laro-e ag-o-re^-ate loss to cotton in India, which may amount to at least one crore of rupees annually. The destruc- tion o£ the seed, the staining- of the and the loss young bolls are jirincipal forms damag-e. So far is known all varieties of cotton now gn-own as field crops in India are attacked, the American and Egyptian as well as the indigenous. It remains to be seen whether there are any varieties of cotton im- FiG. 107. Tarasite on Caterpillar of Pink BoU-morm. [Magnified six times.) mune to the pests, but none have definitely proved so up to the present. Unlike the other boll-worms, this species has not been found attacking plants allied to cotton ; its wild food-plants appear to be trees with oily seeds which are widely distributed in India. Remedies. — The first and most important remedy is to check the increase of the pink boll- worm by plucking off the first crop of bolls if they are attacked. When the first bolls are forming, the first batch of moths lays eggs on them and the boll-worm commences. If left alone these boll- worms will emerge as moths and each lay many eggs. The increase from one pair of moths being large, the second brood is generally a fairly numerous one. Had this first brood been destroyed, it could not have multiplied and destroyed so much cotton later in the season. The second precaution is the treatment of seed by fumigation or other means to destroy the hibernating larvae. Fumigation with carbon bisulphide after the seed has been picked over in the sun is the most effective method of freeing cotton from boll-worms. Equally it is import- ant to pick off the bolls which are destroyed on the plant. Leaving on the plants the bolls that are eaten or destroyed assists cotton pests to multiply and increase. It particularly assists pink boll-worms and the cotton bugs. Other methods of treatment, such as the spraying of bolls with lead arseniate and the use of light traps, are as yet only in the experi- mental stage. 96 PESTS OF THE COTTON PLANT. Generally the picking of the first bolls is praetieuUy the only method that can at present be advised. When the cotton bolls are formed at one season only and the crop ripens (piickly and iiearly simnltaneonsly, this method is capable of g-eneral application ; in the case of cottons that yield slowly and continuonsly over lono^ periods, it is doubtful if a full crop can ever be obtained or even a reasonable proportion of the crop. For such cottons the pest may be regarded as a very serious one. Trap crops of annual cottons may effect something" in the case of valuable tree cottons, if such trap crops are nsed intelligently, but this method also is only in the experimental stage. The Cotton Leaf=RolIer.i A slender caterpillar of a pale greenish colour with a dark-coloured head, which lives upon the lower side of the leaf of the cotton and bhindi plants, folding the leaf over and eating it ; it is easily recognised and is a very common pest of these plants. As a cotton pest it is of some import- ance, especially in the early life of the plant, and needs to be vigorously checked from the outset if it is not seriously to injure or delay the crop. Life Histori/. — The female moth, flying in the dusk or at night, lays her eggs on the lower side of the leaves, one here, one there ; sometimes one on each leaf, often two or more. The eggs are small, round greenish objects, about the same size as the head of a small pin. They hatch in a few days and a tiny slender caterpillar comes out. The young caterpillar feeds upon the leaf gnaw- ing the lower side ; it spins threads over and around it- self as a protec- tion and soon sheds its first skin and grows larger. It then continues feed- ing upon the leaf ', as a rule it turns the edge of the leaf over in a fold *^^ S Fig. 108. Cotton leaves, rolled hy the Cotton Leaf -Holler, (The left hand leaf contains tioo caterpillars.) 37. Sylepta dero^ata, Fabr. (Pyralidse.) ddTTdN LEAF-ROLLER. 9^ and binds it down with silken threads^ living* safely within this fold. As it grows larg-er, it binds more and more folds together, forming' a kind of nest of rolled leaf in wliich it feeds. In those varieties of cotton Avith a large leaf, the whole or a great part of the leaf is thus tied together and if the caterpillar eats much at the base, the leaf withers. In the case of bhindi or of varieties of cotton with smaller, divided leaves, the leaf may be simply eaten, not folded together into a compact bunch. Especially is this the ease in the smaller-leaved cottons, Avhere the caterpillar lives in the top leaves of each shoot and binds them all together. These folded leaves are fairly characteristic of this insect and if opened will be found to contain one or several caterpillars, with a mass of black excrement in grains. [Another caterpillar (the bud caterpillar No. 80) lives only in the top leaves of the shoot, binding them into a very compact mass, which withers and turns dark ; one can readily distinguish this by the appearance of the cater- pillar, of which only one lives in each mass ; it is small, not more than half an inch long, of a distinct opaque dull green colour, not shiny and transparent as is this leaf-roller (see page 99)]. The leaf-roller grows to a length of over one inch; it is slender, the body transparent with a faint greenish tinge, and the dark contents of the alimentary canal showing through the skin 3 the legs are dark, and easily seen, the sucker-feet long and slender. The head and neck are dark brown and there are a few long slender hairs on each segment. After two to three weeks'" life as a caterpillar, the last skin is shed and the chrysalis is formed. This is shiny chestnut brown, with no legs or means of locomotion, about half an inch in length. It lies among the twisted leaves suspended by the threads made by the caterpillar, and is easily found by untwisting the rolled-up leaves. It Hes motionless for eight days and then opens, the moth emerging. The moth is of a whitish colour, with a faint yellow tinge, the wings with many fine dark lines, forming an irregular pattern. It is less than Fig. 109. 3Ioth of Cotton Leaf-Roller. {Magnified.) 08 I'kSTS Oi' TriE COTTON PLANt'. one inch in length, measuring" one and a hali: inches across when the wings are open. It is very easy to rear and recognise ; the brown ehrysahs, if left in a box, will yield the moth in a few days and the moth cannot easily be mistaken for any other moth that lives upon cotton. The moths fly about the fields in the dusk, lying hidden among the leaves during the day. After coupling, the female lays eggs and the moths die. The whole life of this insect occupies from three to four weeks, so that one brood succeeds another rapidly during the warm weather. There are three broods at least in cotton before the cold weather, and as each moth lays many egg's, the pest increases rapidly. With the advent of the cold Aveather, the pest disappears. It is not known to be active during the winter months either in Gujarat or in Behar. It hibernates during the cold weather, reappearing with the rains or rarely before. It is not, therefore, found after November and is a pest to cotton only up to this month. The food-plants include both cotton, holly hock and " lady-finger,'^ 01' bhindi {Hibiscus escidentus). Possibly there are other wild plants on Avliich it can feed. As the latter plant is grown during the rains as a vegetable, the moths that come out in the early weeks of the rains can lay eg^B on it and so there may be one or two broods before it attacks the cotton. It also breeds during the hot weather if plants are available. To both plants it is destructive simply from the damage caused to the leaves. Where it is abundant and strips the plants, it may prove a serious pestj the full yield of cotton not being obtained. One of the common parasites^ a tiny black fly, lays its eggs in the caterpillars ; the eggs hatch to gl'ubs which feed on the caterpillar and finally come out, to form a small egg-shaped white cocoon on the plants ; the caterpillar dies and this insect does much to check the increase of the caterpillar. Remedies. — The pest is not a very easy one to destroy on cotton, and the first consideration must be to prevent its occurrence as far as possible. As the pest comes from bhindi, the best thing is to grow no bhindi at till within reach of the cotton or to grow it in the young cotton plants and tise it as a trap. The indiscriminate growing of bhindi where cotton is also grown is the surest way of helping the pest to attack the cotton. Bhindi should either not be grown at all until November, so that the pest may have no food-plant on which to increase, or should be grown carefully as a trap crop for the pest. In the latter ease, if it is sown between the cotton, it will come up more quickly and the caterpillars win be found first upon it. The caterpillars must then be destroyed and the bhindi plants too, as sOoli as the cotton is large enough to attract the moths to lay eggs* Two months or ten weeks would probably be COTTON BUD CATERPlLLAl?. ^9 tlie time during which the bliindi should be allowed io grow, after which it should be removed and destroyed with all the caterpillars and chrysalides on it. Some will attack the cotton and then can be removed by plucking* all attacked leaves and burning them. This simple method should be applied when the bliindi is removed, if the latter is used as a trap, or as soon as the pest is seen on the cotton. It serves to destroy the first brood on the cotton and so to check the pest from the beginmng". In bad cases of attack on cotton, spraying with lead arseniate is the radical remedy, and where some varieties are grown experimentally, this should be done. Where cotton is grown on a large scale, the pest does little harm as it has so wide a range and does not gather on particular plants. But where cotton is grown on a small scale, there may be so much of the pest as materially to lessen the vigour of the plants, and in this case spray- ing with lead arseniate is necessary. As a rule, the simple remedy of picking off the affected leaves as soon as they are seen is the only remedy necessary. If done in time, it is entirely effective early in the season » The moth has a very wide distribution over the East, from West Africa to Siberia and Australia. It is not recorded as a pest outside India, except from East Africa and doubtfully from the Straits Settle- ments. The Cotton Bud Caterpillar.i A small caterpillar which lives on the top of the shoot of the cottoll plant, binding the leaves together into a small compact knot which turns Fig. ho. Cot/on Bud\Caler];jiUar. [MafjHified four Hii.es.) i*^v,. FXG. 111. Cotton Bud Caterpillar. {Mayr.ifed fovr tin.es) * 80. Fhvcita infusella. Meyr. (Pyralldge.j II a loo PESTS OF THE COTTON PliANT. Fig. 112. Cocoon of Cotton Bud Caterpillar, ti-ith adhering soil. browu. This jJest is easy to recognise from the twisted leaves at the end of the shoot and their withered appearance. The caterpillar is a small opaque g-reeu one, with faint longitudinal lines of browu pigment visible only when examined with a lens. It feeds upon the cotton bud and on the leaves at the tip of the shoot, webbing these together with threads. The small brown pupa is fouud within the twisted leaves. The moth is less than half an inch long, the antennse swollen beyond the basal joint, the palpi upturned; the thorax and basal half of the wings are grey, the apical half being darker. It flies in the dusk and is not readily noticed. The caterpillar is found on the cotton from August to November, after which it hibernates. When abundant, the plant grows short and bushy, and in many cases the insect does good by effecting an even pruning. It is a pest only when abnormally abundant. Indigenous cottons similar to the Broach-Deshi, Goghari, etc., are attacked ; American and tree cottons appear to be immune. The pest is apparently widely spread in India but nowhere seriously destructive. It is very easily checked by pulling off the little dried knots of leaves and bm'uing them with the larva or pupa inside. Spraying with lead arseni- ate also checks it but is not generally necessary. The pest is one that is on the whole of little importance, and generally needs to be checked only on experi- mental farms where the cotton plants are required to come to their full normal vigour. Parasites keep it in check to some extent. Where the mealy bug- attacks cotton, the two pests are found Fig. 113. together, and often the bud caterpillar Moth of Cotton Bud Caterpillar. {3IaffniJied Jive times.) is confused with the caterpillar which feeds upon the mealy bui The Cotton Stem Borer.^ During the growth of liilton plnnis, from tlio iinic the firs< flower buds are formed until the bolls are picked, single plants are found to ^ 60. Sphenoptcra gossypii. Kerr. (Buprestidse.) COTTOX RTEAr nO"RET?. witlior, turn yellow and dio, apparently without cause. If such plants are pulled up and broken across at the crown, it will be found that the centre has been eateu out, a round tunnel extending- up and down the thickest part of the stem. Possibly the insect causing* this damage will be found inside the tunnel, and there can then be no doubt as to the iden- tity of the insect. No other insect is known to attack cotton in this way in India, and if such bored cotton stems are found without the insect, search for other withered or dying plants will probably reveal a plant with this insect at work. Life History. — The grub enters the stem near the crown, hatching from an egg laid there by the beetle. It bores into the stem, feeding upon the tissues as it goes, and making a neat round tunnel up and down the centre of the stem. One grub inhabits a cotton plant and its tunnel sooner or later destroys so much tissue that the plant dies. The grub is white, in length up to one inch, with a slender body, very much swollen into a round, slightly flattened bulb at the front end. The head is small, in front of the swollen thorax, and has powerful jaws with which it gnaws away the wood. Legs are absent and the bulbous swelling fits the burrow in such a way that the larva can move by mus- cular contractions and expansions of this part. When full grown the grub eats a hole almost to the outside, leaving the bark intact, and turns to a chrysalis within the burrow. The chrysalis is white, becoming dark before it emerges, and the legs, wings and antennae of the future beetle may be seen folded against the body. It lies naotionless within the burrow whilst the Fig. 114. Stent Borer in Cotton Stem, 10:; PESTS OP THK COTTON PI,\\T. beetle is gTiulually fonned. Tlie lieeilo iliai oraevg-es is of a dark bronze colour, hard; with leg-s, wiug's and antennae. It measures one-third of an inch in length and is rocog-nisable by its colour, its size and appcaraucr ni its truncated front. It enicrg'es through the thin bark left by the grub. Having- mated, the female beetle lays cg-g's and dies. These beetles are not easily noticed in thej cotton fields. They fly actively and are sometimes found on four irregular Fig. 115. Sfeiii Borer Larva. as many as the leaves of the plant. There may be broods during the cotton season; the "first is a small one and only few plants are destroyed ; the second is a large one, the beetles of tlie first brood laying many eggs ; the third brood is large but is liable to suffer much from parasites ; the fourth brood may be very small and is not important, the cotton having been Fig. 116. Fupa in stem. Fig. 117. Stem Borer Ftqia. {Magnified three times.) Fig. 118. Hole where Beetle emerges. picked before its arrival. These broods are quite irregular and not well marked, since the beetles do not all come out at once. The destruction to the plants will be noticed when flowers come out ; it may be seen earlier, depending upon the growth of the cotton. rOTTON STFAl WEF.VFT., ]0« Tiemeilieft. — Tlio post is easily eliockod if .ill tlie withered plants avo removed regularly and systematically. It is easy to see withered plants, which can be collected and destroyed before the beetle et-capes from them. There is no other simple remedy. It may be found possible to apply a dressing- to the plants that will keep off the beetles and prevent eg-g'-laying-, but the remedy above given is so simple and tliorough, if carried out from the first, that there is no reason to spend money in preventing the first brood from coming. It is better to let it destroy a small number of plants and then make sure of catching it in these plants. Two parasites lay their eggs in the grubs of this beetle in the cotton stem, whicli check it to a slight extent. It is better not to destroy these parasites if they are present in the cotton stems, and this may be effected thus. Place all the stems which are collected in a box or barrel with the lid covered with thin cloth, securely tied down. The beetles and parasites will hatch, the latter being flies easily distinguished from the bronze beetles. The box can be examined periodically and the parasites, if any hatch, allowed to escape. The beetles on hatching will lie motionless in the box and will not attempt to escape if the cloth is quickly lifted, whilst the parasites are active creatures which will fly out of the box at the first opportunity. The parasites wiU then go to the cotton fields and seek for grubs of the beetle in which to lay their eggs. This insect is common in Gujarat, the Deccan, the Central Provinces, and parts of the Punjab. It is rare in Behar and is apparently not so universal a pest as the other insects that attack cotton. There is no record of its occurrence outside India. Fig. 119. Stem Borer Beetle. {Magnijied jive times.) Cotton Stem WeevH.^ A small white grub found tunneling in the stem or branches of certain races of cotton ; the grub is small, less than one quarter of an inch long, distinct in appearance from the stem borer. This pest has been found only in Behar and has not been under observation for any length of time. The small white grub feeds on the tissue of the cotton stem, making twisted galleries which it fills with ^142. (Curculionidse.) 104 PESTS OT" THE COTTON PLANT. Fig. 120. TJie Cotton Stem Weevil. (Afagnified seven times.) excrement. Tlie grub is white, leg-less, not conspicuously swollen in front. It transforms in the burrow to a small white pupa without cover- ing. From this a small weevil emerges, in length about one-eighth of an inch, of a brown colour with black and whitish marks. The insect has a slender curved beak. The weevil is so small and its flight so quick and active that it is not easy to find in the field. They may be found coupling on the cotton plants prior to egg-laying, but are not likely to be seen or recognised. As a result of the attack of this pest, the cotton branch dies or the stem of the cotton plant swells and in a high wind breaks. The peculiar swelling of the base of the stem of the Broach- Deshi cotton plant is a symptom of this pest, and though the plant lives, it may be destroyed in the first high wind. In Behar, the Broach, Goghari and other Bombay-Deshi cottons were attacked in the stems, the Egyptian cottons seriously injured in the same way and certain varieties of tree cotton {Caravonica and others) attacked in the branches. Other tree cottons and many indigenous cottons were on the whole exempt from attack. Once infested the plant is doomed and only preventive measures are effective. Experiments with trap cottons and other trap plants are in progress, and further investigation may reveal some method of checking it. The pest is unlikely to occur only in Behar and may be looked for in other parts of India. Fig. 121. T7ie Cotton Stem Weecil. {3Iagnified seven times.) The Red Cotton Bug.i This insect is the most familiar insect pest of cotton occurring gen- erally in India, attracting attention rather from its vivid colouring than its destructiveness. It is almost identical with the Red Cotton Stainer of the United States and West Indies. The full grown insect measures a little more than half-an-inch from the head to the tip of the wings. Red is the predominant colour, the eyes, the antennae, a spot on the ' 69, D^sdercus cingulatusf. Fabr, (Pyrrhocoridse.) HED COTTON BUG. 105 scutellum and on eaoli wing- beino- black, iho apex of the wings absobitely black and forming when folded a black diamond on the upper surface. Fig. 122. Bug mist alien for Hed Cotton Buff. {From Distant.) Fig. 123. Eed Cotton Biuf. {Magnified.') {From Distant.) Fig. 124. Bug mislaJcen for Bed Cotton Bug. (From Distant.) There are white transverse lines on the lower surface of the body and a tiny white ring behind the head ; the long" sucking' beak lies between the legs. The insect is not likely to be confused if carefully examined, but there are other bug's which have a g-enerally similar appearance, though (hstinct markings. Iii/e Uistori/, — The eg'gs are laid in a loose mass under the surface of the soil, usually in a crack or depression, which the female covers with earth after depositing the eggs. Each e^^ is round, of a light yellow colour ; between fifty and sixty are laid by each female. In less than a week the eggs hatch to small active red insects ; wings are not present, the upper surface of the abdomen being red, with a central row of black spots and a row of white ones on each side. In other respects the young insect is similar to the full grown winged insect. The young moult periodically and grow larger. After the third moult the wings commence to appear as small back lobes on the base of the abdomen. These grow larger at each moult ; there are, as a rule, five moults in all, the insect appearing with perfect wings after the fifth. The male is slightly smaller than the female ; these couple and the females may then be recognised by the swollen abdomen. The red cotton bug also attacks the bhindi plant {Hibiscus esculen- tus) and the silk cotton tree ; enormous numbers are found when the latter is fruiting in April and it breeds extensively at this time. On cotton it feeds on the leaves or stems, but especially on the seeds in the green or ripe boll. It may be found clustered on the bolls, the beak firmly fixed, sucking out the juice, Where either cotton or bhijidi are ]06 PESTR OF THE COTTOX PLANT. -1^ I ' . ■' ^^ w^\, ^^^i^ ^^ ^*^^^ ! Fm. 125. Jied Cotton Buij. plentiful, tho insect becomes very abnndant, increasing rapidly in warm ■\veatlier. This insect has also been reported as attacking- the flowers of Hibiscus at the Saharan- pore Botanical Gardens. There arc no definite broods, insects of all ag-es being- found tog-ether. Reproduction ceases if food is not abundant, the mature insects alone being found. This may also occur in the cold weather, though it is not invariable, and in Western India all stages may be found in the cold weather. ^'''^ If the insect becomes abundant, it weakens the plant and also destroys the seeds. This is the principal damage it causes to cotton, one that is not attributed to the right cause in most cases, as there may be nothing to show what injured the seeds when they are picked. The sucked out seeds are useless for either sowing or for oil extraction, and there may be a very considerable loss from this cause. If the boll is open and the insects congregate among the lint to reach the seeds, the lint may be stained by the excreta, and this form of damage is more readily detected. Jleinedies. — Many methods of dealing with this insect have been suggested, most of them impracticable. The insect being larg-e and vigorous, insecticides require to be very strong- in order to kill it, and this damages the cotton in some cases. A simple method of destroying it in large quantities is to collect the insects by hand. Each cooly has a small grain winnow (soop) and a kerosene tin with a small quantity of kerosene. The insects are shaken off the plant with a smart tap into the winnow ; the winnow is then jerked and the insects fall into the lower upturned portion, from which they are thrown into the kerosene tin. The method is extremely simple and readily understood. Very few insects escape from the grain winnow, and once in the tin their death is certain. The pest is so readily checked by this means that it need never increase excessively. "Where seed for planting is obtained from fields DUSKY COTTON ]MIO. 107 infested witli tliis bug-, tlio seed should ho pickled in a mixture of cow-duuf, clay and water, and then thrown into water, when the sound seed sinksj the worthless seed floatiDg (see page 287). The red bug-s are infested with the magg-ots of a large Tachiiiid fly, which slowly destroy their host and thus form a check on the increase of the bug. The insect is common throughout the plains, in the jungle and in the fields. It hibernates in many parts of India where the temperature falls considerably, and is found in hiding as an imago during the cold weather. Where the climate is suitable it is active throughout the year. The Dusky Cotton Bug.i This insect is well known as a pest to cotton in many parts of India. Though small and insignificant in appearance, its presence in great numbers in the open bolls of cotton has brought it into notice. It has been reported as sucking green bolls and injuring the lint and seed. The insect is found upon the cotton plant, especially in the bolls that open prematurely after they have been eaten by the boll-worm. Large numbers of small brown insects run out of such bolls when they are handled and either fall to the g'round or, if they are full grown, fly away. ^ig. 126. The life history in the cotton boll is very simple. Dusky Cotton Bug. The eggs are laid in the lint close to the seed : each A^^''^^i^^f\ . o° ' [rrom Distant,) Qgg is cigar-shaped, about one mm. long- (^^sth inch), of a brig'ht yellow colour, when first laid. They are laid in batches of G to 10 at a time, and, egg*-laying extends over some weeks. Before hatching the egg turns a bright orange and the emerging insect is the same colour. The newly-hatched insect is about yV^^ inah. long, with three pairs of legs, the usual four- jointed antennae and an enormous proboscis which stretches from the head to beyond the end of the tail. "With this it is able to pierce the cotton and extract food from within the seed. During the next week it grows larger, shedding its skin at short intervals to allow of expansion. The colour gradually alters to a deep reddish brown, darkening at each moult. At the fourth moult the wings appear as small growths on the upper side of the body. At the fifth moult the wings are large but not fully developed, appearino' in their full size after the sixth moult when the insect is mature. The perfect insect is nearly black, one-sixth of an inch in length, with the ' 5. Oxycarosnus latus. Kir^y. (Lygajida).) 108 PESTS OP THE COTTON PLANT. transparent wing-s folded over the back. The female is slightly larger than the male but otherwise outwardly similar. The whole period from the egg to the perfect insect's emergence is twelve days. The mature insects lay eggs and then die. They may live for many weeks before they lay eggs, and if food for their young is not available they wait. Probably they pass the dry weather in the adult condition if no food is available for them, as they may be found on the plants of cotton, etc., at different times of the year. In the cotton season their increase is rapid, the eggs being laid in the cotton bolls. At other times they will lay eggs in the pods of the bhindi (Hibiscus esculfinfus) and possibly of other malvaceous plants, or wait until egg-laying becomes possible. The amount of destruction caused by these insects varies with cir- cumstances. Where there is abundance of worm-eaten bolls, the insects live in these bolls, which open early. They are then credited with the damage done by the boll-worm, as they are the only insect found when the boll is picked. The actual destruction to the crop in this case is small. Where there are no bolls attacked by worm, they attack the bolls as they open and are responsible for damage. The seeds are sucked, the lint is dirtied, and they increase very rapidly in such bolls. The simplest method of treating them is to shake them off the bolls into a vessel containing water and a small quantity of kerosene. The early ripening bolls contain them in great numbers, and by shaking these bolls over a tin pot of kerosene and water they will be killed in large numbers. Worm-eaten bolls, with the insects inside, may be picked off and removed in a bag. There would be a far smaller number of the insect in cotton fields were this done, and the method of testing cotton seed (page 287) should be applied to seed from infested fields. This method of picking off and shaking the bolls may be tedious and long, but it is the only practicable method as a rule. On farms the work can be better done with a spraying machine. It is extremely important to check the pest at the outset when it is breeding in the first opened bolls, and very much better cotton will be obtained w^hen the cultivator takes an interest in his cotton pests and attempts to check them. What is said about testing cotton seed infested with Red Bug applies also to seed sucked by the Dusky Bug. The pest is generally distributed in the plains, though rarely abuitdant. The Cotton Leaf Hopper.^ Among the common insect pests of cotton, the least noticeable is a tiny green fly, which lives on the cotton leaves and flies or leaps out » 82. (J^ssidse.) COTTON LEAF HOPPEli. 109 wiien tlie plant is shaken. It is distinct from the cotton aphis since it is veiy active, both leaping- and flying- ; when it is plentiful, great numbers leap from the cotton plants when they are shaken or disturbed, and this is the simplest way in which to detect the pest. The insect belongs to the family Jassida, leaf hoppers, of which great num- bers live in g-rass or almost any veg-etation ; they are so small as to escape notice. The eg-gs are laid in the tissues of the plant, and the young- that hatch are similar to the full grown insect but wingless and smaller. The food consists of the sap of the leaves, which is extracted by means of the slender sucking apparatus which forms the mouth. The species attacking cotton may be found at all times of the year both in grass and in cotton. Healthy vigorous cotton is less attacked than weak unhealthy cotton ; c- -lo*- ° . , tlG. 127. fewer insects are to be found on vigorous cotton plants coUon Leaf and the leaf hoppers prefer to live on unhealthy plants. As Sopper. . , , PIT ii. • {Magnified.) a pest, the insect has been found only on cotton growing under unsuitable conditions. In 190i, there were plots of healthy cotton and of cotton that had suffered from the drought, growing side by side in one of the Government experimental farms. Few insects could be found in the former, whilst the latter contained enormous numbers. Tliis was observed also in Behar, where cotton was being tried and suffered heavily from the excess of moisture. The absolutely backward cotton was infested, the vigorous cotton was practically free. As a pest then it will be found attacking weak cotton; the result of the attack is that the leaves curl, become discoloured^ wither and fall off. The pest is apt to kill cotton that is struggHng against bad conditions. It appears to attack the larger leaved tree cottons and American varieties more than the smaller leaved Broach-Deshi and Goghari cottons, but will attack every variety if the plants are in bad condition. Evidently this insect cannot rank as a general pest since it will not attack healthy cotton. It is a serious pest in the experimental farnis* where introduced varieties are being acchmatised ; it has also been a pest to many varieties of the American and Egyptian cotton grown in Behar during the wet months. It has been successfully checked by spraying with crude oil emvdsion, at the rate of 1 in 50 of water. An acre of badly infested Goghari cotton treated with a Success Knapsack machine requires 100 gallons of wash, costing Rs. •'3-8, and one day for application. A large amount of wash must be used since it is desired to spray the insects as they come out of the plants in a cloud, and not to spray the plant alone. This is a simple and effective remedy ; no other appears Hkely to be so no tfiSTS Of THE COTTOX PLAJ^T. successful. AVliere it is necessary to lielp a struggling crop tlirougK a bad season, spraying of this kind will be a necessity. When the plants become stronger, they T^'ill not show the disease, and will not be impaired by it. This insect is known from Gujarat, Nagpur, Cawnpore, Lyallpur and Behar at the present time. It will probably be found wherever cotton is grown in India. Cotton Aphis. Small sucking insects found in abundance on the shoots and leaves of the cotton plant ; they are about one-twentieth of an inch long, coloured in dull yellow or black, and have two short processes projecting from the upper surface of the abdomen. This pest is one of the common plant-lice discussed in a later section and has a similar life history. The colonies found on cotton consist of female insects, which produce living young. There is no metamorphosis ; the young are born alive and are all females. After a few days they in turn commence to produce living young ones. Two kinds of females may be seen, unwinged yellowish ones and winged black ones. The latter fly from plant to plant and Fig. 128. Winjed female. {3Iagnified ten times.) Spread the pest over the field. As a rule the young and the unwinged females move but little, feeding in compact colonies on the underside of the leaves or on the shoots ; they extract the sap frcm the plant, making it weak and sickly. The insect appears in the rains and, if cotton plants are available, remains on them until the weather becomes very dry, often until the end of the cold weather* In cloudy weather the ringed ones fly far over the field and found nelv colonies. Hence it is that after the ^B. i4j}liis gosst/fii- Glov. (ApLicla:) fcd'rl'ON APHi^. ill cloudy Avi'atiicr, aphis becomes move a])undaiit and suddenly appears over larg-e ai'eas. Plant-lioe excrete a sugary liquid, wliicli, falling- on the leaves below, dries to a sticky coating. This appearance on the leaves is a sign of the pest and is familiar to cultivators. Many insects attack the cotton aphis and are very im- portant checks upon it ; these are described in a later section under beneficial insects. These insects should be familiar to all who grow cotton and should not be destroyed in error as injuri- ous insects. The treatment for cotton aphis lies in spraying with a contact poison, doing tliis when the first colonies appear on the cotton and not delaying until with cloudy weather they spread over the whole field. If culti- vators Avere familiar with aphis and checked it as soon as they first saw it, it would never become so serious a pest. Without this, large areas may in cloudy weather become aiffiected, and though the pest is principally one on farms and experimental cultivation, it is also an important field pest. Fig. 129. CoHon Aphis, tcint/ed femalo. {^Magnijied jifleen times,) Minor Pests. There are a iiumbei' of insects which attack cotton casually, doing as ft rule no harm but possibly injurious in unusual seasons. The Wliite "Weevil ^ is a small beetle, of a dull Avhiie colour, found upon the leaves of all varieties of the cotton plant almost throughout the year. It bites the leaves of the plant, eating in from the edge. It is most conspicuous from ^ JIi/UocerKs inactdosia: Des L. (Curculionidii'.) in tUSTS OF THli COTTON PLANT. July to October, but has been found at all times. The life history is completely unknown and is apparently not passed in the cotton plant. Special treatment is not required for this pest, which is easily de- stroyed by shaking- it off the plant ; it has a habit of falling- to the ground Avhen disturbed and "shamming dead.^^ The Green Weevil ^ is also a pest of cotton, eating the leaves in the same manner. This insect is larger than the Wliite Weevil, of a dark colour but clothed in metallic green scales, which give it a peculiarly brilliant aj^pear- ance. It is common in Behar and, like the White Weevil, is found also on bhindi, maize and other crops. The Cotton Cater- pillar^ is a green caterpillar, which is found on the cotton leaf ; it walks after the fashion of the true looper caterpillars, hunching- / / JH^ ,t U, ?< ' tad^^ V .^^BS'li/' >'•*«'* i^Bik j^ '^BS^^ >" ~ .•yJB \^ \ / ) J \^ \ Fig. 130. Cotton Aphis, iinwinged female, {Mag nijied fifteen times.) up its body at every step, but is actually a " semi-looper ^^ with three pairs of sucker-feet on the abdomen. The caterpillar is marked with fine white lines and grows to a length of one inch and a quarter. It eats the leaf, making large holes, and finally pupates by turning over the edge and folding it down. The moth emerges after eight days. This pest is not common, is found only during the rains, and feeds also on bhindi and other plants. Another semi-looper found on cotton has but two pairs of sucker- feet on the abdomen and a swelling on the upper surface of the body on the first abdominal segments and the tail. It feeds on the cotton leaf and eventually comes out as a white moth 3 with dark markings. Like the last this is not usually injurious but is likely to be mistaken for a serious pest. '^ Hairy caterpillars which at times ravage large areas of crops also attack cotton and may do much harm. In Behar, the common hairy ^ 188. Asiycus lateralis, F. (Curciilionifla\) 2 115. CosmopMla erosa, HuLn. (Noctuidse.) ^ 162. Taraclie catena. Sow. (Noctuidte.) MINOR COTTON PESTS. 113 caterpillar ^ is found in abundance on cotton throughout the rains if other crops fail it, and this applies also to the Hairy Caterpillar of Gujarat." The very common Red Leaf Beetle ^ is found on cotton but does no harm. The Cotton Mealy Bug is a iDeeuliar species which is found on the top of the shoot ; the shoot swells and twists, forming a hard gall-liko mass and stunting the growth of the plant. Only some varieties of indigenous cottons are affected and the pest is not widely spread. It requires to be destroyed by picking the twisted shoots, or by spraying, as it interferes with the normal growth of the plant. The large spotted grasshopper * is one of the few grasshoppers that is commonly found feeding on this plant. Germinating cotton suffers from the ground grasshoppers and weevils which attack germinating seeds as they push leaves above the ground (see page 220). The ryot sows his cotton so thickly that no damage is done as a rule, but tree cottons and other cottons sown far apart will be eaten if the field is very clean. It is advisable to sow some such crop as maize between the cotton or to leave the final weeding till the cotton has formed two leaves, as the insect then has other food and spares the cotton. 1 136. Diacrisia obliqua. Wlk. (Arctiidae.) 2 220. Amsacta lactinea. Cr. (Arctiidae.) ^ 11. Aulacophorafoveicollis. Kiist. (Chrysomelida».) * 49. Acridium ceruginostim. Burm. (Acridiida;.) CHAPTER IX. PESTS OF RICE AND WHEAT. THE area occupied by these crops is so large that it has not been possible to study adequately their pests in detail. The four chief insects that attack rice and one that attacks wheat are described. There are in addition many insects which appear occasionally, especially those caterpillars which attack rice. In general these are not formidable nor sufficiently abundant to make any impression on the very large area of this crop. The method recommended for dealing with the Rice Grasshop- per should in many cases give good results against these Rice Caterpillars. Wheat appears to sufPer from few pests ; the stem-borer is a specific pest of wheat, cane, etc. The wheat aphis is a serious pest dealt with under the heading "Green Fly and Plant Lice" (page 237). Young wheat suffers from ground insects as do other young rabi crops. Many pests of wheat probably remain to be discovered and any extension of the area under this crop to fresh districts will probably produce new pests. The Rice Hispa .^ A small blue-black beetle, covered the leaves of rice; an infested field becomes yellow, the leaves dying and the plants withering. This pest is a familiar one to cultivators of Bengal and Assam, known by many vernacular names. The small flattened beetle is easy to recognise and the peculiar effects of the attack are fairly characteristic. Life Histori/. — The eggs are laid singly, each q^^ being inserted in the tissue of the leaf, almost exposed and easily visible. The egg is oval, about one-thirtieth of an inch long, and when in the leaf is detected by the white spot and the bvilge in the slit epidermis. It is laid in the upper part of the leaf, not far from the point. The with spines, which feeds upon Fig. 131. Tha Rice Rispa. {Magnified seven times.) ^ 41. Hispa mnescens. Baly. (Chrysomeliclae.) RICE HISPA. 115 egg hatches to a small, flattened grub, with three pairs of legs, which lives inside the leaf between the upper and lower epidermis. The gnib is white or 3'ollow with black markings, very flattened, the first three segments broader than the abdomen. It feeds on the tissue inside the leaf, eating* it away and producing' a large yellow spot. The grub is found by searching for such yellow spots, and the insect may be seen inside if a spotted leaf is held up to the light. The grub when fidl grown transforms to the pupa inside the leaf and emerges as the beetle. The whole life history is passed within the leaf until the mature beetle comes out to fly about. It feeds upon the leaf, eating away the epidermis and causing further destruction. The insect principally attacks the young plants, feeding and laying eggs npon the tender green leaves of the seedling or of the newly trans- planted rice. It is injurious to rice in the seed-bed and shortly after transplanting, the older rice being less attacked and not injured. Wild grasses are the normal food-plants and the beetle flies from the waste lands or jungle to attack the early rice. In some parts of Bengal it is reported to come in enormous numbers, blackening the fields on which it settles and causing a wholesale destruction of the crop. Like the rice-bug it is dependent upon moist conditions and attacks rice that is submerged in preference to rice on higher land from which the water has been run off ; this is the only remedy applied by cultivators, who, when possible, let the water out in the hope that the insect will leave their fields. The insect spends the winter as a beetle in waste lands and grass- lands. The season at which it appears depends upon the sowing of rice and the climate, but lies between April and November. Preventive measures for this pest must be based upon local conditions : where the pest is known to come from a particular place, it may be possible to destroy it there, as, for instance, in the wild grasses in which it lives before the rice is sown, or the sowing and transplanting of rice may be varied to prevent the pest attacking it. In seed-beds the beetle can be destroyed, and if the seed-bed is watched when the beetle is likely to attack it, egg-laying can be prevented. When the beetles come in great number the ordinary bag is sufficient to sweep them up with, and the cultivator is quite capable of using his dhoti or other cloth for the purpose. Any concerted action designed to prevent egg- laying and worry the insect is what is required, and what is, in India, so diflfjcult. When once egg-laying has been performed nothing can be done but to wait for the emerging beetles and destroy them. The use of arsenical insecticides is valuable as a poison for the beetle, but is ineffective against the egg or larva. There is probably little scope for the use of lead arseni9,te, since it will not stand rain and washes off. There is also i8 116 PESTS OF RTCE AND WHEAT. little scope for the use of smoke. Smoke is advisable as a means of checking the insects when they first come as it drives them out of the field ; it has no further effect, kills nothing and is only a temporary device to frighten away the incoming beetles. No specific remedy can be recommended against this pest ; the life history is so safeguarded that there is no obvious point of attack, and reliance must be placed upon preventive measures based solely on local conditions and aimed at destroying the insect in its breeding grounds, securing an earlier or later growth of rice to circumvent the beetle, or making the conditions unsuitable to the existence of the insect. The only available direct remedy is to destroy the beetles with bags, systematically working through the fields and sweeping them clean ; this must be done promptly as soon as the beetles come, and must be thorough. It has been found that certain softer-leaved varieties of rice are more attacked than rough hard-leaved varieties growing side by side, and in these cases the ryot has a remedy to hand. The higher priced soft variety is grown at a risk, when the rough variety might afford an almost certain full yield. The Rice Bug.^ A slender green insect, found flying in the rice-fields, which sucks the sap of the developing ears and causes them to turn white. The insect has an aromatic odour, suggesting geraniums, and may be found in rice-fields when the grain forms. The characteristic symptom of the pest is the whitening ears, a whole field often turning colour in this way. The insect is a typical bug, with no metamorphosis. The eggs are laid in the jungle, as also in the rice crop coming into ear. Each egg' is oval, somewhat flattened, nearly black and very seed-like. They are laid separately, in clusters of four to ten, on the leaves. Fia. 132. The Rice Stiff. (Maffnijled twice.) *103. Leptocorisa varicornis. F, (Coreidje.) RICE BUG. 117 off aud liberatins!: the bug-. Tliey are quite easily seen, the cg-gs forming' a conspicuous object on the "•recn leaf. When ready, the eg'g- opens, the delicate inner membrane and part of one end of the outer shell coming The little bugs are most quaint insects, all legs and feeler?, with a slender green body. The antennae are banded in black, white and brown, the legs black, all extremely long in comparison with the tiny green body. The proboscis is very long, reaching beyond the insertion of the hind legs. At each moult the insect grows larger, the body remaining green. Wings are formed gradually. When full grown the insect is about two-thirds of an inch long, the wings folded over the abdomen, the body green with a tinge of straw colour, the antennae parti-coloured. It flies actively and may be readily Fig. 133. made to fly out of the field. ^^^* ^/ '^" ^''' ^'^^- (^''^'^^J^''^ *'"^''-^ This bug feeds upon ripening seeds; it will attack rice, small millets, grasses and other plants as the seeds form and fill with milky juice. Sama [Panicum Jrumentacenm) is a favourite food, and the bug s normal food is the wild grasses in the jungle and waste lands. Though common in cultivation during the rains, it breeds only when a crop is ripening and food is plentiful. Then the eggs are laid on the leaves of the plant and the young find abundance of food. Cultivators know the pest, which has many vernacular names, but do nothing to check it. It is prevalent in Burma, Assam, Bengal, the United Provinces and Madras, practically throughout the rice districts of India. In other parts of India it is to be found where the conditions are suitable ; it extends to Ceylon, the Malay Peninsula, Malayan Archi- pelago and China. As the winged form is fairly active, it can be driven from the rice-fields with little effort. The unwinged young when dis- turbed simply fall to the ground or to the surface of the water, whence they climb u])on the plants again. There is no easy means of checking it, but if sufiicient trouble is taken and a large area treated, the insect can be destroyed. Ihe simplest method is to draw a bag through the rice, simply running it over the plants. Two coolies can easily manage a bag 118 PESTS OF RICE AND WHEAf. eight feet wide and three feet deep with the opening three feet high. Two bamboos keep open the sides of the mouth and the bag can be drawn tight and rapidly run over the rice, brushing through the upper half of the plant. The winged and unwinged are caught if the bag is at once twisted up at the close of each run and a very large area can be rapidly swept. The method is useless without co-operation, as a whole area must be swept clean or the bugs wander in again. When the flying bugs first come in, the mere dragging of a rope through the crop drives them out again, and a little systematic worrying of this kind sends them back to the jungle. A remedy for this pest used in South India and Ceylon is to smear a paddy winnow with sticky fruit juice, fix it to a pole and wave it in the fields. The insects stick to the winnow if struck. A common hand net is more efficacious and just as easily made, and in actual j)ractice the bag is better still. This method however appeals to cultivators and, if vigorously carried out, does destroy and drive away the pest. In Bengal the rice- fields are found to contain numbers of very active blue beetles, marked with six white spots, which feed upon the rice bug. This is the Six-spotted Tiger Beetle,^ a very valuable predaceous l^eetle which gathers in bug -infested rice-fields and keeps the bugs in check. Another check is a small parasite found in the eggs. FiCx. 134. The Six-spotted Tu/er Beetle that preys on the Rice-Buj. The Rice Stem Fly.2 The first symptom of this pest is the withering of the upper half of the plant, the main stalk bending over from a point some distance above the ground. The upper part withers and the main stem dies. If such a stalk is split up the middle, the maggot or pupa of the insect will be found. Very little ia known of the occurrence of this insect in India, as it has been reported very seldom. The maggots are foun