I4T 



collecting places over an exceedingly large malarial infected area. 

 Owing to the dryness of the atmosphere in this district and during 

 this period, mosquitoes can only exist in close proximity to moisture ; 

 otherwise, from observations made, I have noticed that their bodies 

 soon become shrivelled and the mosquito dies. It is also highly 

 probable that long before all moisture has left the bodies, their net- 

 work of breathing tubes (tracheae) become dry and useless and the 

 mosquito suffocates ; at all events, it will not survive long in a dry 

 climate without uioisture. 



It is natural when the dry weather sets in, for mosquitoes to collect 

 at these permanent water-holes, and here large numbers of anophelenes 

 can be found where they breed and their offspring are enabled to 

 survive the dry period by remaining near the water. During this 

 trying period all animal life concentrates round these water-holes, and 

 the necessary blood without which the female mosquito cannot deposit 

 fertile eggs, is always obtainable. The quiet undisturbed surfaces of 

 these water-holes heavily charged with vegetable matter, form ideal 

 breeding places for mosquitoes. 



A large percentage of the Chenchus (the jungle tribe inhabiting 

 these hills) are heavily infected with malaria, judging from the number 

 of enlarged spleens noticeable, and as their camps at this period are 

 of necessity in close proximity to permanent waters, it is not necessary 

 to look further afield to find the source where the mosquitoes (the 

 survivors of this dry period) become infected each year. This scheme 

 is to attack all these permanent breeding ponds by the introduction 

 of larvicidal fish. The site for the operations has been selected and 

 the work will presently be put in hand. 



II. Red Hills ta?ik scheme. — During the year under report, a 

 scheme was drawn up for utilising the permanent waters of Red Hills 

 and Cholavaram tanks near Madras for the eventual distribution of 

 valuable fish to other parts of the Presidency. The method of opera- 

 tions consists of constructing ponds for breeding and conditioning 

 valuable non-indigenous fish where there is permanent water for 

 stocking the tanks over a number of years. Dealing with these 

 extensive permanent water areas which form the drinking supply 

 reservoirs of Madras is slightly complicated owing to the prohibitions 

 necessary to prevent pollution. This scheme avoids all danger from 

 this point of view which is explained as follows : — 



The site for breeding ^nd conditioning operations has been 

 selected remote from the Red Hills tank (the main drinking supply 

 reservoir) near Cholavaram tank. As netting operations in Red 

 Hills are objectionable from a possible pollution and health point 

 of view, it is necessary to devise other means of procuring the result- 

 ant fry of these stocking operations or, in other words, of winning 

 the harvest for further distribution throughout the Presidency. To 

 enable us to carry this out successfully, we have of necessity to continue 

 the stocking operations over several years with valuable non-preda- 

 ceous species of fish, i.e., to overcome quickly all natural loss (from 

 predaceous fish, etc.) and thoroughly establish the non-indigenous 

 stock. It is the nature of these fish to breed in the reedy places of 

 tanks and for their progeny after a certain growth to migrate up-stream 



