FLIGHT OF ANOPHELES 213 
breeding-places they have traveled passively. They may be carried by a light 
wind but in that case the limit is two kilometers. Dr. J. M. Young, of the 
British Army, after extensive observations in China, came to the conclusion that 
as a rule malarial mosquitoes will not fly over two hundred yards. 
Stephens and Christophers, however, in their reports on the malaria expedi- 
tion to Sierra Leone, state that under some conditions Anopheles may fly much 
greater distances than has been supposed. In one small inland house which had 
been occupied by one old man, five and six Anopheles were to be caught each 
morning. These were fresh from pup and could only be derived from the 
breeding-place three to four hundred yards away. The same writers have also 
demonstrated a flight of six hundred yards. The Royal Society’s malarial com- 
mission in India found that, in certain villages in the central provinces, Anoph- 
eles culicifacies, A. stephensi, and A. fuliginosus were always present if there 
were extensive breeding-places within a quarter of a mile, but that villages which 
were distant half a mile from these breeding-places contained few or no malarial 
mosquitoes. The obvious conclusion is that half a mile was beyond the normal 
flight. James and Liston point out that in Mian Mir three groups of rain-pools 
gave an opportunity to make fresh observations upon this question of flight. The 
first group was four hundred and fifty yards distant from any house; the second 
seven hundred and fifty yards distant; and the third upwards of three-quarters 
of a mile. “On repeated occasions the pools of the first group were found to 
contain larve within a week of a shower of rain, on three out of four occasions 
the pools of the second group contained larve, but on no occasion were larve 
found in the pools of the third group. These experiments appeared to show that 
A. rossi, Which was the species concerned, would readily fly to a breeding place a 
quarter of a mile away, that it would less readily fly to a breeding-place 750 yards 
away, and that it would never fly to breeding places three-quarters of a mile away. 
It is obvious, however, that from none of these experiments can any knowl- 
edge of the maximum flight of ‘ anopheles’ be obtained ; they prove only that 
when these insects are once established in a village they naturally select the 
nearer breeding places in preference to those which are further away. But in 
their search for food adult ‘ anopheles’ often become attracted to villages which 
have no breeding places near at hand, and recent observations have shown that 
they may be abundant in a place even when there are no breeding grounds within 
a very long distance. Captain James, I. M. S., in the operations at Mian Mir 
already referred to, found on one occasion that numerous adult A. fuliginosus 
were present in the bazaars and houses when no larve of this species were to be 
found nearer than two and a quarter miles, and Dr. Christophers, during the 
same operations, found that the limit of flight of A. rossi had not been reached at 
three-quarters of a mile, and that although all breeding places of this species 
had been obliterated up to this distance, it still appeared in increasing numbers 
in the houses. The latter observer draws the following conclusions from his 
experiments :— 
“ (1) In every case where an abundant food supply existed, anopheles 
travelled long distances (half a mile or more) to reach it, and traversed an equal 
