;4 SOUTH INDIAN INSECTS, ETC. [CHAP. X. 



Chapter X. 

 I N S I. C I P E SIS. 



re is no exception to the rule that every organic being naturally increases at so 

 high a rate that, if not destroyed, the eartb would soon be covered by the progeny of a 

 single pair.'' 



Darwin — Origin of species. 



THE word "pest" is so commonly used in connection with 

 insects to denote injurious species thai its meaning is usually well 

 understood, although it is difficult to give any definition of general 

 application. Perhaps it may be said that an insect becomes a pest 

 when by its large number of individuals it does noticeable damage 

 directly or indirectly to man himself or to his livestock, growing 

 crops, stored produce, or other possessions. Such damage may be 

 of regular or of occasional occurrence and may vary from total loss 

 to a very small fraction. Probably damage amounting to one 

 anna in the rupee (i.e., one-sixteenth of the total produce) is the 

 smallest amount that is usually noticeable in ordinary crops, and it 

 is convenient to note the amount of damage in this notation, as 

 one, two, three or more annas in the rupee. 



If we examine any crop under normal conditions it is very rarely 

 indeed found altogether free from attack by insect-pests. Fre- 

 quently half-a-dozen or more different kinds of insects will be 

 found to he attacking it. some eating the roots, others the leaves, 

 some boring in the stem, others sucking the juices, whilst still 

 others eat the buds or flowers or damage the fruit. The damage 

 clone by each inseel may he very small hut the aggregate becomes 

 very large and it is probably a fair estimate to state that on an 

 average ten per cent, of all crops are destroyed by insect-pests. 

 In other words an ordinary normal crop is only nine-tenths of 

 what would be obtained under conditions of total absence i>i 

 damage by insects. It becomes therefore a matter of some interest 

 to attempt to place a money value on this loss, but to do this it is 

 necessary first of all to make a valuation of the annual output of 

 crops. Figures are not available for the whole of Southern India 

 hut the following table shows roughly the figures of area, outturn 

 and value of crops in Madras only, and it must be clearly under- 

 stood that the figures here given do not claim absolute exactitude, 

 i that is impossible, hut they are believed t<> he approximately 

 correct as a whole. 



