392 W. M. ADERS. 



To sum up the position. During certain periods of the year Anophelines gain 

 entrance to the town through a line of small collections of water formed by the rains ; 

 these temporary breeding places soon dry, with the result that most of the adult 

 Anophelines in town die. There are permanent breeding grounds outside the town 

 which constitute the real home of these mosquitos. 



For the purpose of controlling mosquito larvae, several of the larger swamps on 

 the periphery of the town have been drained, others brought into existence during 

 the rainy season are oiled, and a mosquito brigade works under the supervision of 

 the medical officer of health. 



During the last few years three kinds of traps have been used for collecting larvae 

 of Anophelines, Culicines and Stegomyias, respectively. The Anopheline trap 

 consists of a flat tub about six inches in height filled with rain- water and algae, 

 with a small layer of earth sprinkled on the bottom. The Culicine trap consists 

 of a half barrel filled with water rich in decaying vegetation ; the addition of 

 cess-pool water, rice or other organic material forms an attractive bait. The 

 Stegomyia trap is made in the same way as the former, being filled with clean rain- 

 water. I am of opinion that if these traps were used on an extensive scale, they 

 would undoubtedly prove of great use as one method of mosquito eradication. 



Fish imported from the Seychelles {Haplochilus 'playfairii) have been of some 

 use in wells and tanks containing clear water and affording little other animal food. 

 Numbers have been placed in various permanent swamps, their efficacy is still unde- 

 cided. 



As regards the work of mosquito destruction in the town, the great problem is 

 i)he control of C. fatigans, the most prevalent mosquito according to indices of adults 

 taken in the various quarters. Whenever cesspools are opened and examined 

 numbers of C. fatigans larvae are found, generally in pure culture, except in cases 

 where the water is very foul, when the larvae of Pericoma meridionalis reveal them- 

 selves. These small Psychodidae are a common feature in bathrooms and closets 

 throughout the town. 



Practically all houses are furnished with cesspools and cesspits, those of Europeans 

 being provided with earth-closets on the bucket system. The cesspools contain 

 kitchen, bath and household waste water, and in some instances receive a certain 

 amount of storm water. Generally an opening leads from the pantry on the ground- 

 floor direct into the cesspool, affording easy entry for adult mosquitos ; the roofs 

 of the cesspools are also often faulty, thus providing entry for mosquitos. 



Larvae of S. fasciata are found throughout the town area, particularly in native 

 huts, where water is stored in large earth enw^are jars, but also in the iron drums 

 and water-barrels of the Indian bazaars and European quarters. The careful 

 collection of adult mosquitos in houses and their detailed classification and enumera- 

 tion has proved of the greatest value in the search for and the control of breeding 

 places. 



The following natural enemies of mosquitos have been recorded : — 



Larvae of dragon-flies, water-bugs (many species), and larvae of various aquatic 

 €oleoptera. Experimentally the aquatic bugs have proved to be the most rapacious. 

 Nightjars, bats and various species of spiders belongmg to the family Attidae prey 

 on the adults. 



