Flight and Attraction of Mosquitoes 109 



oil. The instrument was used and the results 

 obtained checked with the results of personal ob- 

 servations on both forward and return flight, with 

 the exception of one case, where a male Anoph- 

 eles was apparently traveHng at least temporarily 

 in an opposite direction from the main flight. 



It is possible that where anti-malaria work is to 

 be taken up in badly infested regions observations 

 of flight made in connection with this apparatus 

 wiU indicate which, of several possible production 

 areas, is the principal source of the particular 

 species of mosquito that it is desirable to eradicate. 



One interesting feature in connection with this 

 long-distance flight was that the malaria sick-rate 

 did not increase much although the number of 

 malaria-carrying species of Anopheles present 

 in houses increased enormously. Eight men were 

 employed daily catching mosquitoes in houses at 

 Gatun. The indoor catch of each week and 

 corresponding cases of malaria are given in the 

 table on the following page. 



Although, as already stated, long flights of 

 mosquitoes on the Isthmus were known to some 

 of us, we were tmfortunately unable to trace any 

 individual mosquito and find out by actual obser- 

 vation how far it went, and in what direction. 

 The necessity for this information was apparent. 



