Dr Hindle, The Flight of the House-Fly. 313 
liberated from the ground, but the differences were not very 
considerable. 
When the insects are liberated late in the afternoon, they do 
not disperse in as great numbers as those liberated during the 
morning, but the distances travelled are not inferior. 
With regard to the vertical flight of the house-fly, although 
we have found no means of estimating the maximum, nevertheless, 
when liberating them from the ground, we have frequently ob- 
served the flies at once mount almost vertically upwards to a 
known height of 45 feet. 
Summary. 
(1) House-flies tend to travel either against or across the 
wind. This direction may be directly determined by the action 
of the wind, or indirectly, owing to the flies being attracted by 
any odours it may convey from a source of food. 
(2) The chief conditions favouring the dispersal of flies are 
fine weather and a warm temperature; the nature of the locality 
is another considerable factor, as in towns flies do not travel as 
far as in open country, this being probably due to the food and 
shelter afforded by the houses. 
(3) Under experimental conditions, the height at which the 
flies are liberated and also the time of day influence the dispersal 
of the insects. When set free in the afternoon they do not 
scatter so well as when liberated in the morning. 
(4) From our experiments the usual maximum flight in thickly 
housed localities seems to be about a quarter of a mile, but in one 
case a single fly was recovered at a distance of 770 yards. It 
should be noted, however, that part of this distance was across 
open fen land. 
REFERENCES. 
Copreman, S. M., How tert, F. M. and Merriman, G. (1911). “ An 
Experimental Investigation onthe Range of Flight of Flies.” 
Reports to the Local Government Board on Public Health and 
Medical Subjects. New Series, No. 53, pp. 1—10, with map. 
Hewitt, C. G. (1912). “Observations on the Range of Flight of 
Flies.” eports to the L.G.B. New Series, No. 66, pp. 1—5, with 
. map. 
Hinpie, HE. and Merriman, G. (1913). “The Range of Flight of 
Musca domestica. Experiments conducted in Cambridge.” eports 
to the L.G.B. New Series, No. 85, pp. 20—41, with 13 charts, 
Howarp, L. O. (1911). The House-lly—Disease Carrier. New York: 
F. A. Stokes & Co. 
Jepson, F. J. (1909). ‘Notes on Colouring Flies for Purposes of 
Identification.” Heports to the L.G.L. New Series, No. 16, pp. 
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