Vol. IX. No. 212. 



THE AGRICULTURAL NEWS. 



183 



OUR INSECT FRIENDS AND ENEMIES. By 

 John B. Smith, D.Sc. The J. li. Lipphxrott Co., lOiiU. .>?150. 



This is an iittractive book of some .SIM) page?, written for 

 the general reader and well illustrated with coloured plates 

 and figures in the text. Although written in poimlar style 

 and language, this book is of interest to the .student as well 

 as the general reader, and while it includes a statement of 

 many facts already known, they are presented in such a way 

 as to make them of interest, and to show them in relation to 

 other facts in a way that might not be suspected, even by 

 those who are familiar with them. The titles of the chapters 

 will .serve to give a good indication of the general nature of 

 the work, and each will be briefly reviewed under its heading. 



I. Insects in Their Relation to the Animal Kiogdoni. 

 I'nder this head is discussed the position of insects in the 

 animal kingdom. The anatomy, physiology and life-history 

 of insects as well as a brief outline of the classification of the 

 natural orders are also shortly dealt with. 



II. Insects in Their Relation to Plants as Benefactors. 

 Many insects are beneficial in their relation to plants, among 

 which are to be included principally those which serve for the 

 pollination of flowers, which are so arranged as to require 

 such assistance in the transference f>f pollen from the anther 

 to the stigma, 



III. In-sects in Their Relation to Plants as Destroj-ers. It 

 is in this connexion that insects are generally be.st known, that 

 is, as pests of [)lants, and especially of cultivated plants, and 

 they are more often noticed from the great amount of damage 

 which they are capable of doing than from anj' other cause. 

 In this chapter, the i>rincipal orders of insects are considered, 

 and their liability to occur as pe.sts is discussed. 



IV. Insects in Their Relation to Kach Other. In this 

 chapter is discu.ssed the relation of parasitic and predaceous 

 insects to those other forms in or on which they prey or feed. 

 Insects are among the most prolific of all the forms of animal 

 life, and if it were not for the natural checks which are 

 exercised on this increase, their numbers wouUl soon be sutfi- 

 cient to devour every green thing on the face of the earth. 

 It is due to the habits which certain insects possess that this 

 enormous increase does not occur. 



V. In.sects in Their Relation to the Animals that Feed 

 on Them. In this chapter are discussed the various insect- 

 eating animals, such as birds, toads and reptiles, anil 

 mention is also made of protective colouration and warning 

 colouration, which are siijiposed to be of value to those forms 

 possessing these feature.=, in the matter of protection from 

 their enemies. This is a very interesting chapter, and contains 

 the di-scussion of points not usually considered in dealing with 

 the subject. For instance, it is often taken for granted that 

 any insect-eating bird is almost certain to be beneficial, but it 

 is often overlooked that many of these birds do not discrimi- 

 nate between injurious and beneficial insects, and that many 

 insects which are parasitizeil are oaten. 



VI. Insects in Their Relation to Weather and Diseases that 

 AflFect Them, ^'ery few insects are known to occur in all parts of 



the world. The amount of moisture, as well as of temperature, 

 exercises great influence on deciding whether certain insects 

 can maintain themselves and increase rapidly, some being 

 well adapted to extremes of dryness, and others to extremes 

 of moisture. Sudden changes of temperature and sudden 

 changes in the moisture also affect the conditions of many 

 insects. Numbers of them are subject to attack by fungoid and 

 other diseases, especially in climates where there is a sutticient 

 amount of humidity for these organisms to maintain vigorous 

 growth. This has been taken advantage of in Florida, where 

 fungoid diseases have been used for the control of scale 

 insects un cultivated plants, with good effect. 



VII. In.sects in Their Relation to Other Animals. Many 

 insects are parasitic upon other animals, generally as external 

 parasites. Mosquitos, fleas, lice and bed-bugs attack man, 

 while many others infest other animals, cau.sing disease and 

 financial loss, in many instances. The .screw-w-orm, the sheep 

 bot-fly, and many pests of poultry and other domestic 

 animals, occur in all parts of the world. 



VIII. Insects in Their Relation to Man as Benefactors. 

 I'eihaps the silk worm holds the pre-eminent position in the 

 matter of direct benefit to mankind. The honey-bee is of 

 nearly equal benefit, and several other insects are beneficial, 

 on a smaller scale. 



IX. Insects in Their Relation to Man as Carriers of 

 Disease. In this chapter, in.sects are considered in what ia 

 perha[)s the most important phase of their relationships. 

 •Uosijuitos are carriers and transmitters of such diseases as 

 malaria, tilaria, and yellow fever, and other insects of the 

 order Diptera, w-hich are responsible for the dissemination of 

 tyjihoid fever and sleeping sickness, have been responsible 

 for enormous lo.sses of life, and for preventing the develop- 

 ment of many districts which are extremely suitable for 

 agriculture, except for the abundance of these troublesome 

 pests. As carriers of disease, insects are now known in 

 a role which was almost unsuspected a generation ago. 



X. Insects in Their Kelation to the Household. In this 

 chapter are considered the insects which cause damage and 

 annoyance in the dwellings of mankind. Some of these are 

 important because of their attack on the person, and others 

 becau.se of their attack on furniture, books, fabrics, food- 

 stuffs, and even on the structure of the buildings themselves. 



XI. Insects in Their Relation to the Farmer and Fruit 

 Grower. In this chapter are considered the various pests which 

 attack agricultural crops in a general sense. Under absolutely 

 natural conditions, a balance is quickly established between 

 the animal life and the vegetation. When, however, man 

 intervenes and produces, in a given district, plants that are 

 not indigenous to it, or any of the native plants, in numbers 

 in excess of those in which they occur naturally, this balance 

 is upset and insects appear as pests, in adapting themselves 

 to the altered conditions. Any great increa.se of the area of 

 certain kinds of plants has always led to the development of 

 insect pests and diseases, which it had been necessary for the 

 agriculturist to combat in order to produce profitable crops. 

 To estimate the value of the losses caused by the ravages of 

 insects is rather difficult, but an approximation may be made. 

 It is stated at the close of this chapter, that the annual loss 

 due to attacks of insects in the United States alone, may be 

 estimated at $1,-500,000,000 at least. 



XII. The War on Insects. The concluding chapter of 

 the book deals with the methods employed for the control of 

 insect pests. A brief outline is given of the different kinds 

 of insecticides which may be used, and directions for prepar- 

 ing and using certain of the best of each kind. The 

 niatter of farm practice as related to the control of injurious 

 insects is al.so considered 



