180 
SUPPLEMENTARY ACCOUNT OF THE DIPTEROUS 
LARVAE FEEDING UPON MOLLUSCS. 
By D. KEILIN, Sc.D. 
Beit Memorial Research Fellow. 
(From the Quick Laboratory , University of Cambridge.) 
In my previous paper ( Parasitology , xi. 1919) on the life history of a Calli- 
phorine fly, Melinda cognata Meig., the larvae of which live as parasites in a 
snail ( Helicella virgata), I gave a complete account of all the Dipterous larvae 
feeding upon molluscs. 
Since the publication of my paper several new records dealing with this 
subject have been published or communicated to me by letters. As some of 
this information is yet unpublished while the rest is scattered in different 
journals it may be useful to bring together these records and thus to complete 
the list of observations dealing with the Dipterous fauna of molluscs. 
1. Melinda cognata Meigen. 
Soon after publication of my paper on the life history of this fly, Sir Arthur 
Shipley wrote a popular account of it, which appeared in Country Life , January 
3rd, 1920, pp. 14-15. In reply to this article he received from E. Adrian 
Woodruffe-Peacock a very interesting letter which he forwarded to me. This 
correspondent writes that he has often observed Melinda cognata depositing 
its eggs on Helicella virgata. He has often met with the larvae of this fly and 
he believes that the huge mortality of Helicella observed by him in 1917 was 
undoubtedly due to them. 
2. Sarcophaga Alia Pandelle. 
An interesting account of the life history of this fly has been recently 
given by J. Rostand (1920). This author found in July of 1916 and 1917 at 
Camb (Basse-Pyrenees, France) a large number of a small snail (Helix) har¬ 
bouring Dipterous larvae. The adult flies bred from these larvae were identified 
by Dr Villeneuve as Sarcophaga filia (Rond.) Pandelle. According to Rostand 
the larvae are real parasites since he found them in their young stages attack¬ 
ing almost healthy snails. He compares this case of parasitic life to that of 
Melinda cognata. The larva of S. filia completely devours its host and is trans¬ 
formed into the pupa inside the emptied shell of the snail. 15 days later the 
adult fly emerges. He thinks that there is only one generation per annum. 
