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selected area before beginning to take measures for abolishing breeding 

 places. After completing that preliminary enquiry, the overseer and 

 his coohes begin measures with a " sanitary clean up " inside the 

 house, then they deal with the roof-gutters and cisterns, then with the 

 verandah, kitchen, out-houses and go-downs, and lastly with the 

 compound. Much better results are obtained when the staff allotted 

 to an area is changed once a month than when the same overseers and 

 coohes are kept there permanently. In addition to the check exercised 

 by the system of frequent inspection daily, " independent investiga- 

 tions " afforded a valuable means of ascertaining the correctness of 

 the records made by the regular workers. Whenever possible, the 

 water in a breeding place was got rid of and when, as in roadside 

 gullies and catchpits, this could not be completely done, as much 

 water as possible was removed before applying the larvicide, thus 

 reducing expense and increasing efficiency. A mixture of crude oil 

 and kerosene was first used, but was discarded, as larvae can remain 

 ahve at the bottom of a collection of water for 30 minutes at least, 

 by which time the film of oil has usually become discontinuous. 

 Various preparations of phenol were substituted, commercial cyllin 

 being the most largely used. In practice, a stronger solution than 

 experimentally proved necessary was used, enough cyllin being taken 

 to make the water remain quite milky after it had been well stirred 

 with a stick. This was a rule which the coolies easily understood and 

 followed. For water storage cisterns, carbohc acid was found preferable 

 to oil, its action being more certain. " Trap breeding places " provided 

 a valuable supplementary measure and were a means of preventing 

 the adult insects from seeking out inaccessible breeding places. They 

 consisted of earthenware pots half-filled vnth water, and were removed 

 on every sixth day, their place being taken by a duplicate set. After 

 examination, the trap-pots were well dried in the sun for five days 

 before being used again. 



The traps mentioned in connection with the migratory mosquitos, 

 consisted of a rectangular wood framework 5 feet long, 3 feet deep and 

 3 feet broad, closed with mosquito netting, one end of the trap 

 being a door on hinges. They were placed on the ground in a shaded 

 comer of a garden, a covering of sacking and thick tarpauhn rendering 

 the interior dark and cool. Two or three pots of plants were placed 

 inside each trap and several near the partly open door. The traps 

 were set overnight, and in the morning about 8 or 9 o'clock the 

 vegetation in their vicinity was disturbed as much as possible and 

 straw and paper torches were burnt in all the surrounding out-houses 

 and buildings so as to drive the mosquitos out into the open air. 

 They soon found their way into the cool resting places provided by 

 the traps, the doors of which were closed half 'an hour after the 

 disturbance of the vegetation, and the insects were either killed by 

 placing the traps in strong sunlight for an hour or two or collected 

 one by one in test-tubes by a boy who entered the traps for the 

 pui-pose. No sulphur or other strong smelling substance was used to 

 kill them, as the traps might have been thus rendered unattractive. 



The mosquitos of Colombo comprise 53 different species, of which 

 no fewer than 17 are either dangerous or so numerous as to be a pest. 

 A tabular statement is given of the places in which the common 

 species breed. The staff for the survey campaign consisted of the 



(C89) B 



