ANIMALS WHICH LIVE ON OR WITHIN GROUSE 195 



Although the observations on the animal food of Grouse 

 are necessarily incomplete, 1 enough has been done to show 

 that it is fairly abundant and very varied. From the crop 

 of a single bird there have been taken six saw-fly larvae, eight 

 caterpillars of a Geometrid moth, one caterpillar of a smaller 

 moth, two small Tineid moths, a number of immature bugs 

 resembling the " frog " or " cuckoo-spit," a fly, two specimens 

 of the plant-lice, one small spider, and the remains of four 

 specimens of the slug mentioned above The gizzard of the 

 same Grouse contained, in a more broken up condition render- 

 ing identification more difficult, two or three dozen larvae of 

 saw-flies and moths, some young bugs, and the pupae of two 

 true flies. 



The segments of the Grouse tapeworms containing the ripe 

 eggs pass away with its dejecta and lie on the ground or lodge 

 on the heather and other plants, or in water. As already stated, 

 the eggs of the two species of Davainea are believed to develop 

 into larvae inside the body of an insect or a land mollusc. They 

 are excessively minute, and lying as they do in millions on the 

 heather, may be readily consumed by the leaf-eating cater- 

 pillars and other insect larvae which live on the moors. Doubt- 

 less many are eaten by the Grouse themselves, but these are 

 digested and come to nothing, for they have not reached the 

 larval stage and, as we have said above, the larval stage of a 

 tapeworm must be passed inside an animal quite distinct from 

 that which harbours the adult worm. To get at and eat the 

 eggs seems an easier matter for caterpillars and other insect 

 larvae or for slugs than it is for the ectoparasites, which as a 

 rule are not very likely to come across the dejecta of their host. 

 For this reason, in continuing the search for the* larval tape- 

 worm, it was necessary to examine the insect larvae and the 

 slugs eaten by the Grouse. A common food of Grouse is the 

 head of certain species of rush. 2 There is a very minute moth 



1 See pp. 101 et scq. 



2 Juncus articulatus v. lamprocarpus, J. squarosus, and J. effn&m v. conglomerates 

 are all frequently eaten. 



