THE ECTOPAEASITES OF THE EED GROUSE 365 



and eruption from the attacks of this mite. There seems no doubt as to the species 

 of this mite, but the authorities on these animals express surprise that they should 

 occur so commonly on the Grouse. Our specimens, some of which were taken on 

 freshly killed Grouse, contained some red substance in the stomach, probably blood 

 from the bird. There seems at present little reason to incriminate this mite as the 

 carrier of the tapeworm cyst. They were, however, found by Mr Fryer on a 

 large majority of birds which were especially searched with the view of finding 

 mites. 



(iii.) Fam. Gamasidae. 



IX. GAM ASUS COLEOPTRATORUM (L.). 



We have also taken this common, fawn-coloured mite off the feathers of a 

 Grouse. It is usually found on beetles, but winters under stones, and it is said to 

 die soon if removed from the beetle or from under the stone where it hides, unless 

 it is kept moist. The beetles it favours are usually burrowers in the damp ground 

 or under cow-dung. It probably passes on to the Grouse from under stones. 



GENEEAL DISCUSSION ON THE RELATIONS OF ECTOPAEASITES 

 TO THE ENDOPAEASITES OF THE GEOUSE. 



We have in the alimentary canal three species of tapeworm, two of the genus 

 Davainea and one of the genus Hymenolepis. We know that tapeworms, with 

 perhaps the exception of one species, pass through two distinct and different 

 animals known as hosts. In one animal the parasite lives as an adult, in the other 

 as a larva. The larval host is always, sooner or later, eaten by the host of the 

 adult, and then the larval tapeworm or cyst grows into the adult tapeworm. It 

 was with the hope of discovering the second or larval host of the Grouse cestodes that 

 we began a laborious research on the insects and arachnids which infest the Grouse. 

 Unfortunately, little or nothing is known about the life-history of any species of 

 either Davainea or Hymenolepis. The larval or cystic stages of the former have 

 in some few cases been said to occur in insects and in molluscs ; the larva of the 

 latter is thought to live in an insect or a myriapod, or perhaps even more likely 

 some "water-flea" or other fresh- water crustacean. 



With regard to these possible second hosts ; we have never found a myriapod 

 in the crop of a Grouse, and so far we have not found any Crustacea though it 



