ANIMALS WHICH LIVE ON OR WITHIN GROUSE 191 



ARACHNID A. 



ACARINA. Mites and Ticks, 

 (i) Fam. IXODID^E. Ticks. 



The ticks are now known to carry certain unicellular animal 

 parasites (Protozoa), capable of setting up virulent disease in man, 

 cattle, dogs, etc. They may therefore be of importance in an inquiry 

 into Grouse Disease. It is possible that their presence on the skin 

 may be connected with some of the internal protozoal parasites 

 mentioned below. 



Severe outbreaks amongst fowls of a disease named " spirillosis " 

 and of another obscure but very often fatal disease have been 

 described by Balfour 1 in the Sudan. The organism which causes 

 the former disease, a spirochsete 2 is transferred from one fowl to 

 another by a tick. 3 The second, and as yet rather obscure, disease 

 is recognised by the natives, and by them associated with the presence 

 of the same or allied ticks. We have found little trace of such disease 

 in Grouse, and the recorded number of ticks taken in the Grouse is, 

 except locally, so small that they can hardly play any part in Grouse 

 Disease. 



VII. Ixodes ricinus, Lin. The Common Sheep-tick. 



This species of tick (the " castor-bean tick," as it is called in 

 America) is common in many parts of the world. It is reported from 

 sheep, goats, cattle, horses, deer, dogs, cats, foxes, ferrets, hedgehogs, 

 hares, rabbits, bats, birds, and man. It occurs most frequently 

 during the spring and early summer, but disappears after the 

 beginning of July. 



The sheep-tick is one of the commonest and one of the oldest 

 known ticks of Europe. In the British Isles it often occurs on hunting 

 dogs, and is sometimes called the " dog-tick " ; the adult stage is 

 especially frequent on sheep, goats, and oxen ; less common on horses, 

 dogs, and men. On the other hand, the larvae and the nymphs are 

 common enough on birds, lizards, and small mammals in fact, on 

 animals which live among and brush through grass or heather. It is 

 only in the larva and nymph state that we find these ticks on the 

 Grouse. On each of the infested birds the specimens Were fixed on 

 the chin or round the eyelids in fact, in such positions as the Grouse 

 cannot reach with its beak. In parts of Ross-shire, especially in certain 

 woods, these ticks swarm in enormous numbers, and the keepers 

 declare that they kill large numbers of young blackgame. Hence 

 there is nothing remarkable in finding this species from time to time 



1 British Medical Journal, 9th November 1907, No. 2445, p. 1330. 



8 Probably Spirochceta gallinarum, 3 Argas persicus. 



