GROUSE DISEASE 199 



swallows and other allied species. Recently Dr. 

 Sharp has pointed out that the grouse-fly (0. 

 lagopodis) is distinct from the ordinary bird- 

 fly (0. avicularia). The habits of the grouse- 

 fly are difficult to investigate. It is believed 

 to suck the blood of the grouse, and very pro- 

 bably inoculates the bird with some oi the 

 protozoa or minute animal parasites which infests 

 its blood. The adult or imago burrows amongst 

 the feathers of the bird, and anyone handling 

 grouse during the late summer is apt to disturb 

 a fly or two. Their feet, although large, are 

 very beautiful. Each is provided with a pair 

 of most powerful hooks. Altogether these in- 

 sects have a sinister aspect, and they are very 

 repellent to people who do not like flies. The 

 grouse-fly occurs very frequently in larders where 

 freshly killed grouse have been placed, and after 

 a short time they readily leave their dead hosts 

 and accumulate on the windows. Like the fatal 

 Tsetse-fly of Africa, which conveys sleeping- 

 sickness, they lay no eggs, but produce one larva 

 or maggot at a time, and this immediately turns 

 into a pupa. The pupae of the grouse-fly, 

 usually found in the nest of the grouse during 

 August and September, are black, shiny, seed- 



