CHAPTER XVI 



THE ECTOPARASITES OF THE RED GROUSE [lAGOPUS SCOTICUs) ^ 



By Dr A. E. Sliipley 



Five years ago we knew two internal parasites of the Grouse (endoparasites) 

 and two or three parasites which live outside the skin (ectoparasites). At the present 

 time we know that Grouse, like other animals, have a considerable parasites of 

 fauna living both in and on them. The scientific members of the Inquiry * ^® 

 have recorded nine different species of insect or mite living either amongst the 

 feathers or on the skin of the bird, or in other ways associated closely with the 

 Grouse, and no fewer than fifteen animal parasites living in the alimentary canal, 

 in the blood, in the lungs, or other organs. Some of these are negligible. They 

 either exist in too small numbers or infest but a very small percentage of birds ; 

 others, however, are found in about 95 per cent, of the cases investigated, and two 

 at least are associated with grave disorders which often terminate in death. 



From the point of view of the " Grouse Disease " Inquiry, the attention paid to 

 the ectoparasites may seem superfluous, but many of the internal parasites and all 

 the tapeworms pass through a second host. For example, the tape- 



, _ _ . . Importance" 



worms which live in the alimentary canal of the Grouse pass their younger of ecto- 



*- . parasites. 



or larval stages in the body of some lower animal. This lower animal, 

 presumably an insect or a mollusc or a spider, must be eaten by a Grouse, and the 

 larval tapeworm must be set free before the latter can grow up into the adult 

 tapeworm which we find in the intestine of the Grouse. In searching for this 

 second host it was natural to begin with the ectoparasites, which one would imagine 

 were continually being snapped up by the bird. We have, however, up till now 

 completely failed to find any cestode-Iarvte in the Grouse-fly, or in the numerous 

 " biting-lice " or " bird-lice " (Mallophaga) which abound on the skin and amongst 

 the feathers of the Grouse ; and, what is still more significant and still more re- 

 markable, we have, in the hundreds of crop-contents which we have examined, 

 never found one of these insects in the Grouse's food. 



1 Reprinted from the Proceedings of the Zoological Society of London, 1909, with a few alterations 



347 



