38 LIFE AND HABITS OF DOMESTIC FLIES 



Nuttall and Jepson have made some very careful 

 experiments with various methods of marking flies for 

 the purpose of identification. No method seems to be 

 really satisfactory. The well-known work of Lord 

 Avebury in marking bees, wasps, and ants cannot be 

 as satisfactorily copied with flies, though Graham Smith 

 has traced marked flies 700 yards from place of libera- 

 tion. It is unfortunate, because much information 

 might have been gained by observing marked flies. 

 The house-fly is a powerful winged insect. It can fly 

 stubbornly and apparently knows little of fatigue. It 

 is wonderful how flies will accompany a fast-trotting 

 horse. A small swarm of flies will keep pace with a 

 four-in-hand coach as a school of dolphins will with 

 a steamer going at full speed. Recently, on board a 

 yacht, a house-fly sailed round the Isle of Wight and 

 spent the time walking up and down the glass cover of 

 the compass ; it seemed quite at home in its strange 

 surroundings. Flies will travel a long way in search 

 of food or of a suitable place in which to lay eggs. 

 But, like mosquitos, flies will not volitionally travel far 

 unless they are starving or have no suitable nesting- 

 place. Insects will not fly far merely to gratify 

 geographical curiosity, as some people would have us 

 suppose. If there is plenty of food near a fly-breeding 

 place, they will not leave the vicinity of that breeding- 

 place, and there is no reason why they should. 



But, as emphasised before, more knowledge is re- 

 quired concerning the length of life of individual flies. 

 It is a matter of the utmost importance. There is the 

 possibility that flies live as long as female mosquitos. 

 It is obviously an important matter to know how long 

 a fly may retain disease infection and how long each 

 infected fly can convey disease ; then it might be 



