1909. ] ECTOPARASITES OF THE RED GROUSE. 33] 
OSTRACODA. 
Cyclocypris serena (Koch). 
COPEPODA. 
Diaptomus gracilis (G. O. Sars). 
Cyclops viridis (Jur.). 
Cyclops serrulatus Fisch. 
Also the common freshwater Amphipod, Gammarus pulex 
(De Geer). 
A complete list, so far as was known at that time, of the 
Entomostraca of the Highlands and of the Lowlands could be 
extracted from the very useful Synopses published by Scourfield 
in the Journal of the Quekett Microscopical Club during the years. 
1903 and 1904, 
In none of the species examined have we yet succeeded in 
finding any cysts. 
We have thus with some degree of probability shut out as the 
second or larval host of the tape-worms—at any rate for the 
present—the ectoparasites of the grouse, the myriapoda and 
the slugs or snails, and the fresh-water crustacea, and this on the 
grounds (1) that on examination none of them reveals a cyst, and 
(2) that these animals are either not eaten by the bird, or so rarely 
eaten and in quantities so small as to render it highly improbable 
that any of these invertebrates could account for the almost con- 
stant presence of the cestodes in large numbers in the grouse. 
Two rather striking facts seem to point to the normal insect 
food of the grouse, which it picks up on the moor, as the more 
probable source of the tape-worms. One is, that two of the 
artificially reared grouse at Frimley, which died during the early 
autumn of 1907, were carefully searched for tape-worms; but 
neither Davainea nor Hymenolepis was found. ‘lhe second fact 
is, that the young grouse often contain fully grown Davainea 
before they are three weeks old. They must certainly have 
swallowed the second host when very young, perhaps even the 
day they were hatched, or the worm would not have had time to 
erow. Hence our best chance of finding this second host is to 
examine the crop-contents of the very young birds, and to do this 
we must have a moor at our disposal, and leave to kill as many 
young birds as we may want. 
I have been assured over and over again by sportsmen and 
gamekeepers that the grouse eats no insects, but this is far from 
the truth. 
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.* 
From the crop of a single bird I have taken six larve of 
* 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. The following two paragraphs relate to some observations of my own, made 
in 1905 and 1906. 
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