ANIMALS WHICH LIVE ON OR WITHIN GROUSE 193 



with perhaps the exception of one species, pass through two 

 distinct and different animals known as hosts. 



Unfortunately, little or nothing is known about the life- 

 history of any species of Davainea which includes both the 

 "large" and the " stumpy" tapeworm, or of Hymenolepis, the 

 " transparent " tapeworm of the Grouse. The larval or cystic 

 stages of the former have in some few cases been said to occur 

 in insects and in molluscs; the larval host of the latter is 

 thought to be 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 the Grouse, and so far 

 we have not found any Crustacea though it must not be for- 

 gotten that these are probably so small as to escape notice in 

 the crop contents. Specimens of slugs belonging to a species l 

 which is common on the Staffordshire Grouse moors have been 

 found in the crop of a Staffordshire Grouse. These slugs are 

 very voracious and practically omnivorous ; they 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 round -worms they devour the dejecta of 

 other animals. They prefer the shady places in moors and 

 fields, and emerge into the open only at dusk or when the day 

 is cloudy or overcast. 



These slugs have been cut into sections and diligently 

 searched for cysts of tapeworms, but none have been found. 

 This absence of infection, combined with the rarity of the 

 slug in the Grouse's crop, seems to show that it is not the 

 second or larval host of the Grouse cestodes. 



Moorland streams have been tow-netted for Crustacea in 

 the spring and a certain number of the larvae and adults of some 

 of the water-fleas and other small Crustacea 2 have been found. 



1 Mr W. E. Collinge has identified this slug as Arion empiricorum, Ferussac. 



2 Mostly belonging to the genus Cyclops. A list of species captured, for which 

 we are indebted to Mr D. J. Scour field, is printed in the Zoological Society's Proceedings 

 for 1909. 



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