THE CANADIAN ENTOMOLOGIST 3 



it is known that certain of the flies of the family Cordyluridae prey 

 upon insects which they capture, the common yellow coprophilous 

 S. stercoraria is not usually regarded, so far as I am aware, as a 

 predaceous insect. Yet the observations recently made and for- 

 warded to me (30 Oct. '13) by Mr. George E. Sanders, in charge of 

 the Dominion Entomological Eield Station at Bridgetown, N.S., 

 would indicate that this common species destroys, in the aggregate, 

 no small number of other Diptera, especially Muscid flies, tor 

 which it appears to display a preference. 



Specimens of S. stercoraria were found and taken by Mr. 

 Sanders capturing Mnsca domestica L., Calliphora crythrocephala 

 Mg., Stomoxys calcilrans L., Fannia canicidaris L., Pollenia rndis 

 Fab., and Orthellia cornicina Fab.* After seizing their victims, 

 they wrapped their legs around them and the neck of the victim 

 was then pierced from below by thrusts of the proboscis and sucked 

 for a short time. The body was afterwards turned over and the 

 proboscis inserted between the abdominal segments, in which 

 position the fly continued to feed for a long time. In some cases, for 

 example, Pollenia rudis, the victim's head was completely broken off. 



S. stercoraria was also seen to capture Bibio longipes Loew, 

 and a female of S. merdaria Fab. was caught preying upon Scatops 

 notata L. 



Mr. Sanders reports that Scatophaga has been seen catching 

 Mnsca domestica on the porch of a house, and, when observing the 

 flies attracted by the sugar bait at the laboratory, it was a common 

 sight to see M. domestica captured by Scatophaga. A "yellow fly." 

 probably this species, was reported to him as capturing and eating 

 mosquitoes. 



The preference of Scatophaga for Muscid flies is noticeable. 

 This may be due to the fact that excrement has an attraction for 

 both prey and victims. 5. stercoraria breeds in excrement and 

 commonly frequents it; M. domestica and certain of its allies have 

 similar habits. The significant fact, however, is that Scatophaga 

 preys upon M. domestica and other common Muscids, not only 

 when they are visiting excrementous matter, but in other places, 

 and these facts place Scatophaga in the category of decidedly useful 

 insects. 



*I am indebted to Mr. C. W. Johnson for assistance in determination. 



