1899] GROUSE FLY. 63 



In the above short attempt at differentiation, I have adopted the 

 characteristics given by Dr. J. Eudolph Schiner, in his ' Fauna Austriaca : 

 Die Fliegen (Diptera) ' ii. Theil, pp. 64:4-650, as being tlie best guide 

 which I am personally acquainted with, through the perplexities of 

 synonyms of many previous writers. 



The following short observation of habits of the Grouse Fly was 

 kindly sent me by Dr. W. Somerville, Professor of Agriculture of 

 Cambridge University : — " I am glad to see you have taken note of the 

 Grouse Fly, a creature that has often attracted my attention. In warm 

 weather in August, when one lays Grouse out to cool (as, for instance, 

 during lunch), one has frequently the chance of seeing the fly. It 

 generally runs, but occasionally flies a foot or two, and it is astonishing 

 how rapidly it can disappear amongst the feathers of a bird. It is also 

 very apt to run up one's sleeve, a not very desirable characteristic." 



Besides the usually observed habitat amongst the feathers of the 

 Grouse, I have a note from Mr. 0. E. Janson, F.E.S., with which he 

 favoured me on September 21st in the past season, that, " Strange to 

 say, I have just obtained a very good specimen, which we found alive 

 in a box with a specimen of the Long-eared Owl [Asio otus), which had 

 been sent from the north of Scotland." 



A much more remarkable locality was given in the case of a 

 specimen sent to myself on September 18th from Swansfield House, 

 Alnwick, by Mr. E. G. Wheler, which was found on a Lamb. In this 

 instance I coujecture that from some cause or other the fly had dropped 

 from a Grouse to the ground, or possibly developed from a fallen 

 puparium (as it was a very perfect specimen), and had sheltered in the 

 Lamb's wool as being temporarily at hand. 



How far the presence of Omithomyia on birds may be a source of 

 annoyance to them does not appear to be recorded. From the presence 

 of transverse slanting ridges on the side of the claw (see plate), which 

 we know in the case of the Horse Forest Fly to have an excessive, and 

 most unpleasant power of holding firmly to the hair when opposed to 

 an opposite portion of the claw, it may be presumed the Grouse Fly 

 can similarly hold firmly to the feathers. But unless the " host " was 

 greatly injured by the presence of the infestation, or we had observations 

 of it on the birds in a state of captivity, we do not seem to have means 

 of following up the point. Also it may certainly be believed that if 

 any irritation was caused by the presence of the fly, that the Grouse 

 or other bird would not fail with beak or claw very promptly to dislodge 

 the cause of annoyance. 



I have pleasure in acknowledging all the figures in illustration of 

 this paper as being by the skilled pencil of Mr. Horace Knight, and 

 drawn for me from English specimens furnished by myself. — E. A. 0. 



