Mode of spread of " Anopheles" 



(3) The breeding places of A. fuliginosus were in no case 



nearer than 1,000 yards from the situation where the 

 adults were captured. 



(4) In the later part of the season it was difficult to understand 



where adult A. culicifacies came from unless distances 

 of half a mile or more were traversed by this species. 

 It is obvious that in any attempt to estimate the probable 



efficacy and practicability of efforts at destruction of " anopheles," 



these conclusions are extremely important. 



MODE OF DISPERSAL. 



The usually accepted fact that " anopheles " do not disperse any 

 considerable distance from the place where they were born may also 

 be contested. In our opinion, which is based chiefly upon observa- 

 tions made by one of us, and by Dr. Christophers, in Mian Mir, four 

 ways of dispersal of " anopheles " are constantly in action in India, 

 viz. : 



(1) By direct flight over considerable distances. Examples 



of this method have already been given. 



(2) By eggs and larvae being carried long distances by 



streams and canals. 



(3) By the gradual spreading of "anopheles" adults in all 



directions, by short stages, from areas in which they 

 are abundant. This results from the fact that all 

 newly hatched mosquitoes do not return to the house 

 or village from which their parent came, but fly to 

 houses in the opposite direction ; and having found 

 their food there, proceed to breeding places still 

 further removed from the original village. 



(4) Adult mosquitoes are constantly conveyed sometimes 



long distances in carriages, carts, and other vehicles. 

 This must be a matter of common observation to any 

 one who has occasion to travel much in India. 



Observers who consider that " anopheles " can be materially 

 reduced in numbers by the obliteration of all breeding places in the 

 immediate vicinity of dwellings, rely chiefly upon the suppositions 

 that the range of flight of these insects is very limited, and that 

 they do not disperse any considerable distance from their breeding 



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