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INSECTS INJURIOUS TO MAN AND STOCK IN ZANZIBAR. 



By W. M. Aders. 



Order DIPTERA. 



CULICIDAE. 



Zanzibar Town is roughly divided into two halves, the European quarter, with 

 the Indian Bazaar, and the native African town, these two districts being separated 

 by a tidal creek. The European quarter (where most of the Government officials 

 and Europeans reside) is on the western side in close proximity to the sea. The 

 periphery of the town is surrounded on the land side by various swamps, all of them 

 potential mosquito-breeding areas during certain seasons of the year, some of them 

 permanent throughout the year. 



There are two rainy seasons during the year ; the heavy rains generally commence 

 about the middle of April and last mitil the end of May or the first week in June. 

 The rainfall for April, May and Jime dming the last three years was as follows : — 



The small rains break about No\'ember and are of three weeks duration. These 

 two rainy seasons greatly influence the prevalence in to\Mi of Anophelinae and 

 various species of Culicinae. During the dry season Anophelinae are of rare occur- 

 rence in the town, one might say practically non-existent, judging by the mosquito 

 brigade returns. There are certain permanent Anopheline breeding grounds out- 

 side, and on the periphery of the town ; shortly after the rains set in, a chain of 

 small swamps, pools, etc., are brought into being, which act as intermediate breeding 

 grounds for Anophelines and are responsible for their eventual arrival in the town.. 

 During May and June Anopheline larvae are fomid in small numbers throughout 

 the town ; as their breeding grounds dry up the adults die off, to reappear during 

 the next rainy season. 



The following table shows the catches of Anopheline larvae in the town during 

 April, May and Jmie for the last three years : — 



April 



May 



June 



(C357) 



