646 MR. G. S. COTTERELL ON THE LIFE-HISTORY 



Breeding takes place regularly' from April to October, and 

 there are probably five broods a year. 



No definite results were obtained on hibernation, but evidently 

 a large number hibernate as adults. A number of pupae were 

 exposed to cold weather during December, but the adults all 

 emerged without exception. This implies that hibernation does 

 not take place in the pupal stage, but it may be that the process 

 of histogenesis had proceeded beyond a certain point before being 

 placed in the cold, and the breaking down and building up of 

 tissues in the pupje Avere carried on. A large amount of adults 

 are seen about on warm sunny days in winter, but 90 per cent, 

 are males. I think that probably the majority hibernate as 

 adults, but that only those females survive that failed to ovi- 

 posit before the cold weather set in. This would account for the 

 difference in proportion of the sexes. Probably a few survive 

 the winter as puparia and the larger proportion as adults. 

 Investigations extended over another winter would proA^e this 

 point. Graham-Smith remarks that S. stercoraria hibernates as 

 a resting larva or pupa in the soil, a few surviving the winter 

 as adults. 



A number of flies were placed in a glass-house heated by two 

 electric radiators. During one night the temperature rose to 

 over 90° F., with the result that they were all found dead the 

 following morning. It appears from this that the fly is not 

 capable of withstanding high temperatures. The fly is, however, 

 a subtropical one as well as a temperate one, and should there- 

 fore be able to stand this temperature. The sudden change from 

 a mild temperature to a hot one and the lack of ventilation were 

 probably the cause. It must also be remarked tliat the flies 

 were of a very large variety. The largest and smallest varieties 

 are not so resistant to unfavourable conditions as the average 

 sized varieties. 



The food of the adults is very varied, but confined to other 

 Diptera. The small Borborid fly [Borborus equinus) appears to 

 be the chief article of diet in the field, chiefly as it breeds 

 abundantly in horse excrement and as it passes the winter as an 

 adult. Larger flies, however, are preyed upon, such as Calliphora, 

 Lucilia, M. domestica, etc. Probably all species of Diptera are 

 preyed upon, with the exception of those of fast fiight, such as 

 Syrphidse and Stratiomyidse. I observed, on one occasion, a 

 large male attempt to capture a small dung-beetle {Geoti'upes) 

 as the latter was settling. At the Zoological Gardens in 1915 

 Professor Lefroy's experiments with fly-traps were interfered 

 with by the abundance of the adult S. stercoraria that fed on the 

 trapped flies, chiefly blow-flies of the genus Calliphora. 



In summer the adults may be seen on plants and flowers far 

 away from pastures waiting for other flies to settle in the vicinity. 



M. domestica was used as food almost entirely in the laboratory, 

 each fly sucking out as many as a dozen a day. 



