59 



of ten days. Powdered borax, both as a solution and in powder form,, 

 is effective, or it may be burnt in a tightly closed room. Strong 

 solutions of creosote, or creolin, or some commercial contact insecticides 

 have proved successful. Carbon bisulphide fumigation may be used 

 in the strength of 12 lb. per 1,000 cubic feet of space. Hydrocyanic 

 gas is also effective, but more dangerous to use. 



'*^ Lassalle (C. F,). Trinidad Malarial Report, Vori of Spain 1916, 126 pp. 

 [Received 28th February 1917.] 



The second section of this Report contains a survey of the Anopheles 

 of Trinidad, and includes reports from various districts of the Island, 

 detaihng the breeding places discovered and the measures employed 

 for control. All surface drains in villages should be properly graded 

 to a suitable outfall and concreted as far as possible. Earth drains 

 should be kept free of vegetation and oiled once a week. All low-lying 

 and swampy lands, as well as useless shallow wells and ponds near 

 villages, should be drained and filled in. If practicable, a pipe-borne 

 constant water supply should be introduced in every village. This 

 would render it possible to do away with shallow wells and water-holes, 

 as well as cisterns and tanks. Where a pipe-borne supply is not 

 possible, the efficient screening of all water receptacles should be 

 secured. Borrow-pits should be filled in or, when very extensive, 

 should be efficiently drained towards the nearest water- course. The 

 current of streams should be accelerated by the regular removal of 

 obstructions, such as vegetation, debris, etc., the courses being 

 straightened wherever possible. In the vicinity of villages water 

 collections which cannot be immediately dealt with should be oiled 

 once a week, or fish, if they can live, should be put in them. 



The oil which has proved best and cheapest is a mixture of crude 

 petroleum and some lighter oil, such as kerosene or distillate oil, only 

 a very small quantity of the latter being necessary to render the crude 

 oil thinner and allow of its being used with a spray. This can be 

 apphed with an ordinary watering-can with a fine rose, or by means of 

 pieces of rag dipped in the oil and scattered over the surface of the 

 water, or a spraying machine may be used. In the case of large 

 collections of water near villages, a barrel of oil may be so placed as to 

 allow of the oil dropping constantly through small holes at the bottom. 



For rice-fields one method advocated is a system of pisciculture, 

 which has been very generally adopted in other parts of the world. 

 Experiments would have to be carried out to ascertain the variety of 

 fish best suited for the purpose in each locality. Another measure 

 recommended is the periodic drying of rice-fields, which, if properly 

 carried out, does not damage the crop. 



The third section of this report deals with Trinidad mosquitos. 

 A short classification, after Theobald, is given and a key to the various 

 species now known to exist in the Island is added. 



An appendix deals with the association of fish with Anophehne 

 larvae, giving particulars as to the localities where they have been 

 found together. 



In an appended report by J. D. Leacock, particulars are given of 

 mosquitos found during surveys of special districts. 



The following list of species is given as occurring in the island : — 

 Anopheles apicimacula. D. and K., A. punctimacula, D. and K., 



