120 Major E. E. Austen on the 



"with experiments out of doors/' This statement, it must 

 he admitted, leaves something to be desired, since it is not 

 clear whether the Blow-flies, when attacked, were or were 

 not at liberty. In the subsequent paper, however, all doubt 

 is set at rest by Mr. Cotterell himself, who writes (loc. cit. 

 p. 646) : — "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.''' 

 Comment is scarcely needed, though it is perhaps per- 

 missible to point out, merely by way of illustration, that 

 should a hungry leopard happen to find itself shut up in a 

 cage with a litter of young Ijadgers, and should that happen 

 which under the postulated conditions would be most likely 

 to occur, it would be unwise to draw from the tragedy any- 

 thing like a dogmatic conclusion as to the favourite diet of 

 Felis parclus. 



Now as to what happens in nature, concerning which Prof. 

 Lefroy's statements have been given above. Mr. Cotterell 

 {loc. cit.) writes: — ''The food of the adults is very varied, 

 but confined to other Diptera. The small Borborid fly 

 {Borbonis 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, how- 

 ever, are preyed upon, such as Calliphora, Lucilia, M. domes- 

 tica, etc.'' It will be observed there is a curious discrepancy 

 between the statements of Prof. Lefroy and of Mr. Cotterell, 

 which as regards the most important detail are even mutually 

 exclusive, since, while the former claims that S. stercoraria 

 "■ specially attacks Calliphora and Musca,''^ the latter asserts 

 that Borborus equinus, Fin. (a small, narrow-bodied, bronze- 

 black fly, measuring some 4*5 mm. in length, and perhaps 

 not one-twelfth of the bulk of an average specimen of 

 Calliphora erythrocephala) " appears to be the chief article 

 of diet." 



The evidence bearing upon the prey of the Yellow Dung-fly 

 published prior to Mr. Cotterell's paper, albeit extremely 

 scanty, does not support Prof. Lefroy's contention. Thus, 

 according to Kirby & Spence"^, " Scatophaga stercoraria and 

 scyhalaria .... feed upon small flies, . . . ." Again, at a 

 much later date, Prof. Poulton f gave records of the prey of 

 seven specimens of Scatophaga stercoraria " as the result 

 of the observations of five observers in several very difierent 



* 'Introduction to Entomoloi>y,' 5th ed. vol. i. p. 275 (1828).— 

 Quoted by Poulton, Trans. Ent. Soc. Lond. 1906, p. 394. 

 t Traus. Ent. Soc. Lond. 1906, pp. 391-392. 



