86 the habits and bionomics of the house-fly 



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. Kamnierer 

 (1908), however, experimenting with Al. domestica and C. vomitoria, 

 has found that if the wing is extirpated from the recently pupated 

 fly it is occasionally regenerated. The new wing is at first homo- 

 geneous, and contains no veins, but these appear subsequently. 



Longevity. 



The difficulty of experimentally determining the length of the 

 natural life of a house-fly can be appreciated only by those who 

 have attempted it. Those who have not done so will hardly realise 

 it. Few insects are more difficult to deal with under experimental 

 conditions. One would imagine that these insects flying about 

 everywhere as they do, could be easily kept in a large roomy cage 

 if given the necessary food and water. In my experience, however, 

 this has not been the case ; I have never succeeded in keeping 

 flies alive in captivity for a longer period than seven weeks. 

 In the winter it is apparently more easy to keep them alive in 

 captivity. Jepson (1909 b) kept alive for eleven and a half weeks 

 flies which had been reared in confinement in Februarv. Flies 

 which had been caught in the kitchens during the same month, 

 and were, therefore, probably flies of the previous autumn, were 

 kept in captivity for ten weeks. Jepson states that in the 

 summer he was unable to keep flies in captivity for more than 

 three weeks. Griffith (1908) succeeded in keeping a male fly 

 alive for sixteen weeks. The evidence which is available clearly 

 indicates, I think, that the late autumn bred flies, if they 

 escape death from Empiisa and other causes, live through the 

 winter to produce eggs in the following spring. I am inclined 

 to regard the winter breeding of M. domestica as unnatural, as 

 it is induced by conditions which are, strictly speaking, artificial. 

 The summer flies are probably shorter lived owing to their ex- 

 tremely active lives which endure probably for about two months 

 or so. 



