366 THE GROUSE IN HEALTH AND IN DISEASE 



must not be forgotten that these are probably so small as to escape notice. We 

 have found in the crop of a Staffordshire Grouse one species of slug which Mr 

 W. E. Collinge has kindly identified for us as Arion empiricorum Ferussac, a 

 species of slug which is common on the Staffordshire Grouse-moors. He tells 

 me that the slug undoubtedly belongs to the genus Arion, and almost certainly 

 to Ferussac' s species A. empiricorum, a name included by J. W. Taylor in his 

 " Monograph of Land and Fresh-water Mollusca of the British Isles," 1 among the 

 synonyms of Arion ater (L.). The well-known difficulty of identifying slugs which 

 have been preserved and which have lost their colour accounts for the slight doubt 

 that exists. Arion empiricorum is very voracious and practically omnivorous ; it 

 will eat almost anything, especially decaying animal and vegetable matter, fungi, 

 paper, weak and injured worms and slugs, and what is interesting from the point 

 of view of the Grouse tapeworms and roundworms it devours the dejecta of 

 other animals. It prefers the shady places in moors and fields, and emerges into 

 the open only at dusk or when the day is cloudy or overcast. The following 

 parasites which may give rise to adult forms in the Grouse have been found in 

 A. empiricorum : 



. TREMATODA (Flukes) : 



(1) Cercariacum limacis Duj. 2 



(2) Cercaria trigonocerca Dies. 



CESTODA (Tapeworms) : 



(1) Cysticercus arionis v. Sieb. 



(2) Cysticercus tcnnice arionis v. Sieb. 



NEMATODA (Roundworms) : 



(1) Leptodera angiostoma Duj. 



(2) Leptodera appendiculata Schneider. 



(3) Nematodum limacis atra v. Sieb. 



(4) Pelodytes hermaphroditus, Schneider. 



We have cut one of these slugs into sections, and have sought diligently 

 through them for cysts of tapeworms, but have found none. This absence of 

 infection, combined with the great rarity of the slug in the Grouse's crop, seems to 

 show that A. empiricorum is not the second or larval host of the Grouse cestodes. 



1 Leeds, Part XI. p. 167. 



2 Full references to the literature where these are described are given in my original Paper in the Pro- 

 ceedings of the Zoological Society, London. 



