76 SOME SOI III INDIAN INSECTS I [CHAP. \. 



i this table it will be seen that the average annual crop-outturn 

 oi Madras is upwards oi eighteen hundred millions of rupees, and 

 this fi nol include the produce of nearly thirteen million 



acres under forests. Applying the ten per cent, rule of insect 

 dam e figures, we find that the destrui tion 01 i asioned by 



insect-pests every year maj be placed at not less than two hundred 

 millions of rupees, of which roughly one-halt is accountable to 

 t-pest of paddy. 



V el i \ en the above figures do not represent the total damage to 

 the State wrought by insects, lor they take no account of the 

 economic loss caused by insect-carriers of diseases to man and his 

 domestic animals. These latter alone represent a money-value of 

 at least six hundred millions of rupees and e\ en a small percentage 

 on this figure runs into a very considerable amount, whilst diseases 

 carried by the various ticks, lice, biting-flies and fleas that infest 

 such animals are only too common. The ravages of Malaria and 

 Plague maybe cited as those of only two hum. in diseases, both of 

 which are solely spread by the agencj of insects, and the annual 

 death-roll in Madras from insect-borne diseases may be placed at 

 upwards of two hundred thousand. Nor do these details exhaust 

 the catalogue of crime suffered by man at the hands (or. rather 

 mouths) of his insect foes, for his various possessions — his stored 

 food, his clothes, even his houses and all woodwork used for con- 

 struction purposes are not exempt from attack. Totalling the 

 damage to crops, domestic animals, stored products and other 

 possessions and to man himself, we may therefore estimate the 

 damage done by insects ever) year in Southern India at not less 

 than three hundred millions of rupees (Rs. 30,00,00,000). It is sin- 

 cerely to be hoped that, by the development and application of 

 entomological knowledge, this enormous wastage of national wealth 

 may be reduced in the future. 



Turning now to the causes which conduce to such vast losses, 

 at least in the case of growing crops, we find that they are due as 

 a nth' to one ol the' following conditions, (i) the placing of large 

 areas under one class of crop, (2) deafforestisation and other alter- 

 ations of natural features due to human agency, (3) the introduction 

 of non-indigenous pests and crops, (4) the destruction of birds and 

 Other i"' ; 11 eous or parasitic- enemies, although all these conditions 

 are often mutually interdependent and sometimes inseparable. 



In the preceding chapter it was seen that, under the natural 

 conditions of existence, the c-normous natural rate of increase of 

 any species of insect is neutralized bj the destruction wrought 

 amongst its individuals and then descendants, so that its numbers 

 in any given ana remain approximately constant, enemies and lack 



