Vol. Xxiv] ENTOMOLOGICAL NEWS 453 



L. O. Howard, in his excellent volume on this pest, gives a 

 whole chapter upon its natural enemies. These, as the author 

 states, "begin with the acme of the vertebrate series (man him- 

 self) and end with the lower forms of plant life." Among the 

 natural enemies listed are included : fungous diseases, protozoa, 

 nematodes, mites, spiders, the house centipede, predaceous and 

 parasitic insects, birds, and fly-catching rats. The parasite 

 which I have to report is of biological interest chiefly, yet those 

 interested in economic entomology may be glad to note that 

 another natural enemy has been recorded for our dreaded 

 Muse a domestica. 



HABITS. 



For several years the writer has noticed that a house fly is 

 occasionally found flying about with a rather large gamasid 

 mite hanging to it. I have caught many such flies in houses 

 and in laboratories, and others have sent to me flies which car- 

 ried this mite upon their bodies. I never have noticed more 

 than a single gamasid upon a single fly, and this individual has 

 usually been found running about on the body of its host. It 

 is well known that flies, as well as many other insects, carry 

 non-parasitic mites, especially of the family Gamasidae, where- 

 by the distribution of the latter is effected. Beetles, especially, 

 may carry a score or more of non-parasitic mites upon their 

 bodies for long distances. In fact I have frequently found 

 such individuals almost or quite concealed by scores of the 

 nymphs of the genus Uropoda, all of which were getting a 

 "free ride," though these injured their pseudo-host in no way. 

 For these reasons I paid little attention to the first gamasid 

 mites found on flies. 



While at Ithaca, New York, my attention was frequently 

 called to house flies that carried this gamasid mite. Upon an 

 investigation I succeeded in rinding mites that had their cheli- 

 cerae inserted into the ventral body wall of the fly, and in one 

 case the mite remained so attached after being killed, along 

 with its host. 



When these mites feed upon the house fly they attach them- 

 selves always at a definite place. This is at the base of the 



