(124) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 365 



and disease-germ-carrying powers. Normally they do not fly 

 great distances. They may be compared to domestic pigeons 

 which hover about a house and the immediate neighbourhood. 

 On sunny days they may be found in large numbers out-of- 

 doors, but they retire into the houses when it becomes dull or 

 rains. They are able to fly, however, a considerable distance, 

 and can be carried by the wind. A few years ago, when 

 visiting the Channel Islands, I found M. domestica from 

 H to 2 miles from any house or any likely breeding-place, 

 so far as I was able to discover. Dr. M. B. Arnold has 

 made some exact experiments at the Monsall Fever Hospital, 

 Manchester, on the distance travelled by flies. 1 Three hundred 

 flies were captured alive, and marked with a spot of white 

 enamel on the back of the thorax. These were liberated in 

 fine weather. Out of the 300 five were recovered in fly-traps 

 at distances varying from 30 to 190 yards from the place of 

 liberation, and all the recoveries were within five days. 

 M. domestica is also able to fly at a considerable height 

 above ground, and I have found them flying at an altitude of 

 80 feet above the ground. Such a height would greatly 

 facilitate their carriage by the wind. 



4. Regeneration of Lost Parts. 



If the wings or legs ofM. domestica are broken off they 

 do not appear to be able to regenerate the missing portions, 

 as in the case of some insects, notably certain Orthoptera. 

 Kammerer (1908), however, experimenting with M. domes- 

 tica and C. vomitoria, has found that if the wing is 

 extirpated from a recently pupated fly it is occasionally 

 regenerated. The new wing is at first homogeneous, and con- 

 tains no veins, but these appear subsequently. 



1 Recorded on p. 262 of the ' Report on the Health of the City of 

 Manchester for 1906,' by James Niven, 1907. 



