122 Oil the Pre;) of the Yelloio Damj-Fly. 



but a normal-sized Calliphora erytJirocephala, after being 

 l)ouncecl vipon by a Yellow Dung-fly, could hardly pass 

 unnoticed, since such a victim would be much broader and 

 bulkier than its captor. If, therefore, as Prof. Lefroy main- 

 tains, S. stercoraria is really " a constant and general feeder 

 on the common species of Blow-fly in England throughout 

 the season,'^ the present writer feels his previous ignorance 

 of the fact to be well-nigh inexplicable ; otherwise he can 

 only regard his failure to notice even one solitary case in 

 point as due either to singular ill-fortune, or to an invariable 

 purblind n ess or lack of observation far more reprehensible 

 than anything read of in our youth in the edifying tale of 

 " Eyes and No Eyes.'' Another reason for doubting 

 whether S. stercoraria preys normally and by predilection 

 upon C. erythrocephala is that, as a general rule, the two 

 species do not occur together to any extent. Of course, 

 Blow-flies and Yellow Dung-flies may, and doubtless fre- 

 quently do, encounter each other in certain places, such as 

 in country gardens or on the flower-heads of Angelica, 

 Heracleum, and other umbelliferous plants in ditches and 

 hetlgerows ; and no one would wish to deny that under such 

 conditions an occasional Blow-fly may succumb to the 

 rapacity of its yellow-coated neighbour. Generally speaking, 

 however, Calliphora erythrocephala does not wander far from 

 human habitations, and is therefore not likely to come very 

 much into contact with S. stercoraria, which, as everyone is 

 aware, is most in evidence on cattle-droppings in pasture- 

 fields, pj-actically throughout the year. Even C. vomitoria, 

 L., the other British representative of the genus Calliphora, 

 does not on the whole haunt the same spots as the Dung-fly. 



Turning to the evidence of other observers. Prof. E. B. 

 Poulton, F.R.S., has kindly given permission for the repro- 

 duction of the followilig extract from a letter recently 

 received from him. " Since 1906," writes Prof. Poulton, 

 " further material, somewhat larger in amount, has accumu- 

 lated in the Hope Department of the University Museum, 

 Oxford, chiefly as the result of the investigations of Mr. A. 

 H. Hanmi. The prey, as in the earlier series, consisted of 

 small flies from various groups, Prof. Lefroy's conclusions 

 being partially supported by only a single example — Scato- 

 phaga ordinata '^' with a very small specimen of Calliphora 

 vomitoria as its prey (Paignton, April 10, 1914). 



" There can be no doubt that the species Scatophaga, 

 in the wild state, rarely attack any but small flies, and 



* A species in which the male is smaller and less hairv than in 

 S. stercoraria, L. — E. E. A. 



