STRUCTURE, ])F]V£LOFMENT, AND BIONOMICS OF HOUSE-FLY. 365 
and disease-genn-can-ying 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 lai’ge 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 ]\[. domestica from 
ItV 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.' Three hundred 
flies were captured alive, aiad 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. 
1\I. 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 of M. 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. 
Kanimerer (1908), however, experimenting with M. domes- 
tica and C. vomit or ia, 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. 
' Recorded on p. 262 of the ‘ RepoiT on the Health of the City of 
Manchester for 11*06,' by Janies Niven, 1007. 
