212 3I0SQUITOES 



in malarious neig-liborlioods cannot be too strongly in- 

 sisted upon, wherever there is any reason to suppose that 

 any work which may have been carried on against breed- 

 ing-places may not have been so thorough as to be effect- 

 ive. If mosquitoes of the malarial genus Anopheles 

 once gain access to a house they will remain hidden 

 behind curtains or somewhere upon the walls during 

 the day and at night fly out about the rooms in their 

 search for iDcrsons to bite. Some observers of tropical 

 countries say that in unprotected houses, Anopheles 

 will frequently fly out and hide outside during the day, 

 returning to the houses at night, but by far the more 

 usual method seems to be to stay indoors. In addition 

 to this screening, it is recommended that in tropical 

 countries all the indoor walls of houses should be 

 painted white or whitewashed, in order that the dark 

 bodies of the mosquitoes may plainly" be seen and that 

 they may easily be caught. However, when the walls are 

 not white and when the insects are hidden behind hang- 

 ings or behind old-fashioned beds or elsewhere, they 

 may be driven oiit of their hiding-places with smoke and 

 will then settle on the window-panes in the hoi^e of es- 

 caping. 



To kill living Iiiosquitoes in houses, Fermi and Lum- 

 bao recommend chlorine gas. Pour into a dinner plate 

 containing four or five spoonfuls of chloride of lime five 

 to ten cubic centimetres of crude sulphuric acid. This 

 liberates the chlorine gas, which kills the mosquitoes. 

 The same w^'iters state that the vapors of chloral act rap- 

 idly, killing them in a few seconds, though these vapors 



