204 The Control of Mosquitoes ■ 



some of these cars. A camp consisting of screened 

 cars, and a tent hospital screened in the manner 

 outlined above, have been in use for about four 

 years. Although Anopheles were very numerous, 

 as shown by the daily catches in the cars, and 

 although very little oiling, etc., was done in this 

 locality, the screening, plus daily catch of mos- 

 quitoes in the cars, kept the malaria incidence 

 to almost the average incidence of the Canal 

 Zone. 



The crucial point about screening is the thor- 

 oughness with which the work is done, and the 

 constant vigilance and care that must be exercised 

 in speedily detecting and remedying defects. 

 Mosquitoes, and particularly Anopheles, will 

 readily find a very small aperture in their endeavor 

 to enter a house to find blood, but once within a 

 house, the mosquito very seldom, if ever, finds 

 its way out again unless doors or windows are 

 open. A screened house with rents in the screen- 

 ing, cracks in the floor, openings between the plate 

 and roof, or any of the many imperfections of 

 mosquito-proofing, is a veritable trap, and from 

 the point of view of the protection of its inhabitants 

 from mosquitoes, more dangerous than an un- 

 screened house. 



A perfectly screened house may yet offer in- 



