60 GROUSE. [1899 



of which up at least to 1888, the species aviculariu appears to have 

 been the only kind recorded as present in Britain, is of some interest 

 from the peculiar structure of its claws. (See frontispiece.) 



The Grouse Fly, as well as the Horse and the Deer Forest Flies, 

 belongs to the division of the Pupiparo, or pupa-bearing flies, charac- 

 terised by their young not being produced in egg or larval state, but 

 as pupce. That is, the larval growth takes place inside the abdomen 

 of the female, and it is produced, or, popularly speaking, laid, as a 

 pupa, or just at the time when the change from the larval (or maggot) 

 state to that of the pupa is taking place. Previous to the exclusion, 

 the abdomen of the mother tiy is noticeably much enlarged ; and 

 contrariwise, when the pupa has been deposited, the shrunken state of 

 the abdomen is strikingly observable. 



In the case of the puparium figured at p. 59, the mother Grouse 

 Fly was sent me on August 13th from Swansfield House, Alnwick, by 

 Mr. E. G. Wheler, with the observation, "I am sending you a Grouse 

 Fly, which I hope may reach you alive. It is evidently a female with 

 pupa." On receipt of the specimen, I forwarded it undisturbed to a 

 friend for microscopic setting, who remarked in reply : — " As I noticed 

 its abdomen was very small and collapsed, I concluded it had deposited 

 its puparium, and on examining the pieces of hay in the tube I found 

 it attached to a small fragment ; so have taken it out, and send it on 

 to you. . . . It is at present very transparent, so I imagine the 

 fly will not emerge for some time yet." 



From the deposit taking place after the female had been secured 

 in the tube, I was thus enabled to secure a specimen of the puparmm 

 for figuring that without doubt belonged to the Grouse Fly ; but the 

 pupa having apparently been killed by the journey, I had no oppor- 

 tunity of observing its changes after birth. In the very early condition 

 in which it is figured (see p. 59), the somewhat mamillated or deeply 

 corrugated posterior extremity of the puparium very much resembles 

 one of the figures given by Keaumur =■• of the puparium of Hippobosca 

 equina before it had assumed the wholly brown colour which it gains 

 shortly after birth, and also the smooth surface and merely emarginate 

 end of the posterior extremity of the mature puparium. 



The fly (O. avicularia) much resembles the Horse Forest Fly in 

 general appearance, but is smaller, not being more than a quarter of 

 an inch in length ; somewhat elliptical in shape, flattened, and tough, 

 or leathery. The colour variable, being sometimes of a yellow horn 

 colour, sometimes the upper side is almost brown, and sometimes the 

 light parts are of a bright green. (In my own specimens the green 

 tint was not present.) The head round, flattened, with two knife- 



* ' Histoiie des Insectes,' par M. de Reaumur, torn. vi. pi. 48, tig. 12, mem. 14. 

 Paris. MDccxLii. 



