Fig (VIII)
5.
Ornithomyia lagopodis (Sharp). Dorsal view. to people who do not like flies. The grouse-fly occurs very frequently in larders where freshly killed grouse have been placed, and after a short time they readily leave their dead hosts and accumulate on the windows. Like the fatal Tsetse-fly of Africa, which conveys sleeping-sickness, [GROUSE they lay no eggs, but one larva or maggot emerges from the female at a time, and this rapidly turns into a pupa. The pupæ of the grouse-fly, usually found in the nest of the grouse during August and September, are black, shiny, seed-like-looking objects. Probably each pupa takes some three-quarters of a year to develop into the adult fly, and the latter disappears from October until June. We have never found one of these flies in the crop of the grouse, nor have we succeeded in finding cysts in the bodies of flies which were broken up, or teased up, or cut into sections.
Family. SCATOPHAGIDE. 6. Scatophaga stercoraria (Lin.).-The maggots of this family of fly live in the bodies of other insects or upon festering sores, or in organic material. The larva of the species in question is found in grouse droppings. Hence we imagined it would be a likely host for the cestode cysts, but here again we drew a blank.
Acarina (Mites and Ticks).
Family. IXODIDE. (Ticks.) are 7. Ixodes ricinus (Lin.) are now known to convey from one vertebrate host to another a large number of unicellular organisms which cause disease in man, cattle, dogs, &c., and it may be that they convey to the grouse some of the protozoa which are mentioned below. Ixodes ricinus is one of the commonest and bestknown ticks; it is found on sheep or dogs, and is termed indefinitely the sheep-tick, or the dog-tick. It also occurs on oxen, horses, and men.
The earlier stages in the life-history of the tick, that of the larva, and the second of the three stages, the nymph, occur on birds, lizards, and small mammals-in fact, on animals which live amongst and brush through grass and heather, or the undergrowth of a wood or forest-and it is these stages alone which are found on the grouse.
The ticks were always in such a position, either on the chin or round the eye-lids, that the beak of the grouse cannot reach them. In parts of Ross-shire, especially in certain woods, these ticks are said to be extremely numerous, the keepers aver that they frequently kill off large numbers of black-game. They are commoner during the spring and early summer, but usually disappear at the beginning of July.
A disease named Spirochætosis, one of the most fatal diseases which attack fowl in the Soudan, is transferred from one bird GROUSE] to the other by a tick known as Argas persicus, and it may be that Ixodes ricinus is capable of conveying some injurious organisms, but at present there is no evidence of this. Family. TYROGLYPHIDE. (Cheese- and Flour-mites.) 8. Aleurobius farina (Degeer). This common flour-mite was discovered by us living on the skin of the grouse, rather to the surprise of the authorities on Acarines.
It appeared to be most common in March, and less abundant in July. Some of our specimens, taken from freshly killed grouse, contained a red substance in their stomach, probably the blood of the bird.
Apart from this, they seem to cause little harm.
The endo-parasites, or those which live inside the body of the grouse, are responsible our knowledge of their life-history; hence the stress which has been laid on the external parasites which may function as the second or larval host of some of them.
CESTODA.
Family. TAENIIDÆ. (Tape-worms.) 9. Davainea urogalli (Modeer). Of the three tape-worms that are found in the