142 THE CANADIAN ENTOMOLOGIST. 



According to Dr. Riiiherford, the fly was first recorded as a serious 

 pest in Ontario about twenty years ago, from whence it spread to other 

 parts of the Dominion. 



In reading Austen's British Blood-sucking Flies, 1906, I note the 

 following : "In the British Isles this (L. irritafis^ H. serrata) seems to 

 be an uncommon pest" (Lieut. -Colonel Yerbury). This statement appears 

 to me to be significant, and I am convinced that it is worthy of further 

 investigation. 



In the course of the summer iwo other flies were found infested with 

 mites, one a Sand Fly, Ceratopogo?i sp. ?, the other I cannot name ; it 

 annoys cattle, however, by sucking up the serum which exudes from the 

 wounds made by other flies. The Sand Fly has been scarce this summer, 

 but as in the case of the Horn Fly, further evidence is needed to see if 

 other influences rather than the mites were not the cause of their diminu- 

 tion in numbers. 



I am indebted to Dr. J. G. Rutherford, C.M.G., Veterinary Director- 

 General, for permission to publish this note. 



Explanation of Figures Illustrating Dr. Hadwen's Paper. 

 Figs, i, ii and iii. — Pigmeophorus americanus Banks. 

 Fig. iv. — Tyroglyphid Hypopus. 

 Fig. v. — P. arnericaiius on H. serrata. 

 (Original photographs by S. H.) 



Note on Dr. Seymour Hadiven^s Paper. — The Horn Fly, Hcematobia 

 serrata Rob. Desv., was first recorded in Canada in the summer of 1892, 

 when it caused considerable alarm in Ontario and Quebec. The species 

 of mite infesting H. serrata has been kindly identified by Dr. Nathan 

 Banks as Pigmeophoriis america?ius Banks. He informs me that this 

 mite, which belongs to the family Tarsonemidse, has been previously found 

 in the Western U. S. on a fly of the family Platypezidae. This species is 

 illustrated in the accompanying figures i, ii and iii. Fig. iv, which was 

 occasionally found, is the Hypopal stage of a Tyroglyphid mite, which is 

 using the fly as a means of transportation. The relation of these mites to 

 the flies upon which they are found is not always that of a parasite ; 

 sometimes they may feed, and in other instances the fly is merely acting 

 as a disseminating agent. I have occasionally found certain Gamasid 

 mites, truly parasitic, on dipterous insects. — C. Gordon Hewitt. 



