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EXPERIMENTS AND OBSERVATIONS UPON GLOSSINA 



PALPALIS. 



By Dr. J. W. Scott Macfie, M.A. 



West African Medical Service. 



In Northern Nigeria the dry season begins in October, and ends in March. 

 During this period practically no rain falls, and the highest temperatures of the 

 year are recorded during the day, whilst the lowest annual temperatures occur 

 during the night at this season. A short tornado season occurs at the beginning 

 and end of the dry weather. In the case of Zungeru, where my experiments 

 were carried out, the following is the meteorological return for the year 1910 : — 



ZUNGERU. 1910. 









Temperature 



(Fahrenheit). 



Rainfall. 



Wind. 



Month. 



Shade 



Shade 







Amount 



Degree 





maxi- 



mini- 



Range. 



Mean. 



in 



of 







mum. 



mum. 







inches. 



humidity. 





January 



102 



57 



45 



78 





34 



N.E. 



February 



.. 



.. 



102 



62 



40 



83-7 



— 



33 



N.E. 



March 







107 



65 



42 



86 



•83 



36 



N.E. 



April ... 







103 



70 



33 



87-7 



1-15 



61 



S.W. 



May ... 



. , 





101 



69 



32 



835 



6-69 



73 



s.w. 



June ... 







95 



66 



29 



80-9 



5-54 



79 



S.W. 



July ... 







91 



67 



24 



78-7 



7-09 



82 



s.w. 



August 



• . . 



. , 



90 



68 



22 



78 



19-27 



86 



s.w. 



September 







92 



67 



25 



78 



10-82 



84 



s.w. 



October 







96 



61 



35 



81 



2-05 



77 



Yarious. 



November 



. . . 





98 



57 



41 



79 



— 



42 



N.E. 



December 







99 



60 



39 



79-7 



— 



37 



N.E. 



Year 



... 





107 



57 



50 



81-2 



53-44 



60 



N.E. & S.W. 



It will be observed that both the maximum (107° F. or 41*6° C.) and the 

 minimum (57° F. or 13*8° C.) shade temperatures occurred during the dry season, 

 and that whereas the average degree of humidity was 80*8 for the five months 

 (May, June, July, August and September) of the rainy season, it fell to 36*5 for 

 the four months (November, December, January and February) during which 

 no rain fell. 



As the dry season advances the tsetse-flies ( G. palpalis), which in the rainy 

 season are more widely distributed over the country, gradually shrink back 

 towards the rivers, until in January they are only to be found in a few patches 

 of bush along the river banks. The causes that help to bring about this change 

 in the distribution, which first suggest themselves, are, the greater degree of 

 coldness of the nights, the unclouded hot days, and the diminished humidity of the 

 atmosphere due to the dry harmattan wind which, at this season, blows down 

 from the north-east. The object of the experiments described below was to 

 determine the relative importance of these several factors. 



