370 THE GROUSE IN HEALTH AND IN DISEASE 



Although the observations on the animal food of Grouse are still incomplete, 

 enough has been done to show that it is fairly abundant and very varied. A fuller 

 report on the insects found in the Grouse- crop is given by Mr J. C. F. Fryer in the 

 Interim Report of the "Grouse Disease" Inquiry, published in August 1908, and 

 in chapter iv. 1 The following two paragraphs relate to some observations of 

 my own, made in 1905 and 1906. 



" From the crop of a single bird I have taken six larvae of Tenthredinidae (saw- 

 flies), eight caterpillars of a Geometrid moth, one caterpillar of a smaller moth, two 

 small Tineid moths, a number of immature Homopterous insects resembling the 

 ' frog ' or ' cuckoo-spit,' a fly, possibly a Leptis, two specimens of the family 

 Aphidse (plant-lice), one small spider and the remains of four specimens of the slug 

 Avion empiricorum Fe"r. The gizzard of the same Grouse contained, in a more 

 broken-up condition, and consequently more difficult to identify, two or three dozen 

 larvae of saw-flies and moths, some young Homopterous insects, and the pupae of 

 two Muscid flies. 



"The segments of the Grouse tapeworms containing the ripe eggs pass away with 

 its dejecta and get on the ground or on to the heather and other plants, or into 

 water. The eggs of the two species of Davainea are believed to develop into the 

 cestode larva 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 caterpillars and other insect larvae which live on the moors. 

 Doubtless many are eaten by the Grouse themselves, but they are digested and 

 come to nothing. As we have said above, a tapeworm must have a second or inter- 

 mediate host, and its larval stage must be passed inside an animal quite distinct 

 from that which harbours the adult worm. To get at and eat the eggs seems to 

 me 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 looking for the larval tape- 

 worm, we have sought the insect larvae and the slugs eaten so eagerly by the 

 Grouse. A common food of Grouse is the head of certain species of rush. Juncus 

 articulatus v. lamprocarpus, J. squarrosus and J. effusus v. conglomeratus are all 

 frequently eaten. There is a very minute moth the larvae of which live in curious, 

 white, papery cases inserted into each twig of the rush-head which they eat. When 

 the rush is in its turn eaten by the Grouse the larvae of the moth pass into the 

 alimentary canal of the bird and are there digested. It has not been possible to 



1 Chap. iv. p. 88 et seq., vol. ii. Appendix E. 



