278 Annals Entofnological Society of America [Vol. IX, 



appears that in two camps so nearly alike we ought to expect 

 about the same number of cases in each. The increase of 250% 

 in camp 15 is due to the fact that on account of no traps, more 

 mosquitos entered the building, and therefore the higher 

 malarial rate. 



The weekly summary for these two camps is represented in 

 the following chart. The weekly index was gotten at in the 

 following manner. If during the week twelve collections were 



r\ 



CAMP 5 



\A 



h 



Chart A 



made in camp 5, then the total mosquitos (anophelene only) 

 caught in that week were divided by twelve. This gave an 

 average per one catch per week. The same was done with 

 camp 15. Then the average catch of both camps for the same 

 week was added together and considered as 100%. The fol- 

 lowing notes should be read in connection with the curve. That 

 portion of the chart included within the series of arrows repre- 

 sents data for camps 5 and 10 for during that time camp 10 was 

 used as a W-I barrack. Both camps had four traps each, but 

 camp 10 had but one door while camp 5 had two. Very often 

 extreme fluctuations are due to existing cracks in the floor 



