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pounds sterling in the next year, and the crop has since been normal. These remedies were not introduced into Sind, and in 1906 the cotton crop there was again a failure tiil, in 1907, we applied remedies and produced a normal state of things. We have campaigns of this sort going on year by year in India and in our Colonies, and it is this class of work that our entomologists are constantly engaged in. There are many problems to be solved, but the experience of the past has shown that the appli- cation of entomological science to similar problems has been very largely successful. Nor is this sort of large combined campaign the only method that has proved successful; probably greater aggregate good is done by teaching farmers about their pests and by means of lectures, leaflets, and coloured illustrations, giving them reliable information, teaching them how their pests live, and giving them the best technical information about remedies and insecticides.
This is the main work of the economic entomologist, and the success of it depends upon its accuracy, its practical utility, and its being available to every farmer or planter who requires it. To do this work requires a thorough know- ledge first of pure entomology; it is based upon a groundwork of thorough know- ledge as a whole, and before any beginning can be made, very thorough training is required. It is this training which we hope to give, rendering available for England and the Empire men thoroughly skilled in entomology, able to apply themselves to practical problems without having to acquire a knowledge of entomology to begin with.
In other ways also, the influence of destructive insects is fully shown; our cattle and domestic animals suffer from insects in a very marked way; the warble in cattle is stated to affect over 48 per cent. of the hides exported from Indía, and the loss in the value of American cattle passing through Chicago in six months was put at over three million dollars; sheep suffer from maggots in the brain, horses from bots in the stomach, and most of our valuable domestic animals have parasites of one kind or another.
In forestry the influence of destructive insects is very marked; in nature, where the forest is undisturbed, matters adjust themselves to a large extent, but the earth is being cleared of natural forest and man is making forestry a business in which artificial conditions are established, the natural law is upset, the balance of life is altered, and outbreaks of insect pests become a very serious matter. The loss annually in American forests is put at twenty million pounds, and the losses in tropical forests are probably much higher; in planting and working large areas, in the preparation of working plans for felling and re-planting successive areas, the influence of insects and the methods of meeting them cannot be neglected, or the losses from this cause become enormous.
Nor is this loss confined to the growing plant or animal; from the time it is harvested to the time it is consumed, grain, timber, and foodstuffs must be guarded and protected; the ravages of weevil in wheat and rice amount to a very serious total, especially in hot countries. In India, the loss in wheat amounts to over a million pounds sterling annually, and the loss in rice to probably three times that on the average.
Flour, meat, dried fish, dried fruits, almost every form of food
must be preserved very carefully if insects are not to infest it. We have had to deal with flour moth in flour mills, with beetles in brush factories, woollen clothing stores, and leather factories, with beetles in tobacco factories, and with boring beetles attacking bamboos, wood, and the like. In the tropics the white ant is a very destructive agent; a commission is working now on the railway sleeper problem in India, the white ants finding railway sleepers excellent food in some parts of the country, and this problem involves a very large amount of money. Every working entomologist has abundant experience of these and similar problems, and it is an important part of his work to cope with these pests.
Here in London, in a temperate climate, you will think I am drawing an exaggerated picture, but I am not doing so, and if I take my illustrations from the tropics very largely, it is because it is there the cases are the more striking and numerous, and because I have worked there so long. The problem is the same here. and the pioneer work in England of Curtis and Miss Ormerod in the last century showed what losses there were and started the development of the subject.
In all these cases, whether on crops, domestic animals, or stored products, there is but one way of meeting the problem, and that is, first study and then the applica- tion of common-sense remedies based upon that study. We can do nothing until we know our insects, know how they live, where they lay their eggs, how long the eggs take to hatch, where the grub lives, how it feeds, how long it lives, and every detail
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of its life from start to finish. That is a matter of scientific enquiry, and it is only on this knowledge that we can base our remedies or preventive measures and hope to either fight the pest or show farmers how to do it for themselves. We have to study the insect as a living being, to keep it in captivity and breed it, to watch it in the field, to find out its enemies, its peculiarities, and really know its life and habits at all seasons of the year before any progress is possible. There is no magic that we can use, no one perfect simple remedy that fits all cases, no universal insecticide; for each case careful study, then experiment in the field, and then, with the co-operation of the farmer, the testing and application of remedies on a large scale. It is with this that scientific entomology is concerned, and it is only in this way that progress is possible. In India the cultivator will tell you that the caterpillar that bores in his canes comes from the well water he irrigates with; a little investigation shows that the caterpillar comes from eggs laid in clusters on the leaves of the cane, and that, with some borers at least, these eggs can be cheaply and simply removed. This is a very simple instance of what I mean by the study of the pests' habits, and every successful remedy or preventive is a similar instance. The economic entomologist does this only, and his object is to find a weak spot in the life history of the insect, where, by some simple measure or by some modification of the local agricultural practices, he can destroy the insect or make its occurrence impossible.
In all the cases I have mentioned up to now, insects affect man indirectly, but the last twenty years have shown that insects have a great significance also as carriers of disease to man and to domestic animals, and we are here confronted with a very large and difficult problem. It is common knowledge now that malaria is com- municated to man by the bite of one of several kinds of mosquitoes; to those who have lived in the tropics the significance of this will be obvious. Few Europeans in the tropies escape malaria; many die from it. and the mortality from malaria among Europeans and natives in a bad season may be awful. Since this discovery was made, it has been found that other diseases are carried by mosquitoes and other biting insects; yellow fever is carried by a mosquito common in the tropics, so is filariasis by other common mosquitoes; the rat flea is the agent which spreads plague: the tiny midge of the genus Phlebotomus carries Pappataci and similar fevers; the large flies of the genus Glossina carry sleeping sickness of man and similar trypano- some diseases of cattle, horses, and dogs. The common bed-bug is suspected, but not definitely convicted, of carrying kala azar and similar diseases. It is no exaggera- tion to say that these discoveries opened a new field, and, when one considers the dreadful mortality these diseases cause, a very wide one. The significant point in attacking these diseases was thought to be the germ or organism carrying them; but the insect is now shown to be at least as important and, in many cases, a far more attackable point. Plague in India has been a terrible scourge and might be so in Europe; but the plague flea and the plague rat are far more easily controlled than is the plague germ, and it is on them that the spread of the infection depends
Let us see what occurs in plague. A plague rat, that is a rat infected with the plague germ, is, we will say, let loose in London or anywhere you please; its fleas suck its blood and draw in the plague germ; the rat gets worse and dies. As its body gets cold, the fleas leave it to seek another rat or some other warm animal on which they can live; they bite that animal and give it plague also, thereby infecting other fleas, which leave that rat when it dies. Now, were these fleas only to bite rats, the disease would stop there, but they do not. They bite man also, incidentally, and he gets plague, and probably dies of it. That is why, in India, when rats begin to die, the people at once have to avoid being bitten by a flea from a dead plague rat, and if they are wise they leave their houses. Now, clearly, here one link is the flea, and we want to know all about it: where does the flea come from, where does it lay its eggs, how does the grub live, and so on. Instead of using disinfectants to kill the germ, which was supposed to live in the dirt of the house, we now use insecticides to kill the fleas and to prevent them breeding. One reason why Europeans in India seldom get plaque is because they live in clean houses, where fleas cannot breed or live. If there is going to be an epidemic of plague in England, it is to the plague rat and the plague flea we must turn our attention.
The problem is, then, to a large extent an entomological one, and so, in all insect-borne diseases, it is the insect we have to study and to fight. Here again it is in the tropics more than in England that the work lies, and it is perhaps difficult for anyone who has not lived and suffered in the tropics to realise the immense importance of entomology in this respect. However one lives, mosquitoes and sandflies bite one, the flea comes off the dead rat and jumps on to one, the bed-bug
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