. l^'iG. 18 (a). Fig. 19 (b). Fig. 20 (c). Fig. 18.—Adult Female Gad-Fly—slightly enlarged. Fig. 19.—Full-grown Grub—natural size. Fig. 20.—Head of full-grown Grub—highly magnified—showing hooks by which the Grub attaches itself to the mucous membrane. itself into the nostril and disappearing in the nasal passage. In one day—nearly all spent in observing this single sheep—eighteen of these larva were deposited on its nostrils, and it appeared that but one fly was engaged in the business that day. The rest of tht flock had hidden near a fallen tree in the pasture, thrusting their noses close to
. l^'iG. 18 (a). Fig. 19 (b). Fig. 20 (c). Fig. 18.—Adult Female Gad-Fly—slightly enlarged. Fig. 19.—Full-grown Grub—natural size. Fig. 20.—Head of full-grown Grub—highly magnified—showing hooks by which the Grub attaches itself to the mucous membrane. itself into the nostril and disappearing in the nasal passage. In one day—nearly all spent in observing this single sheep—eighteen of these larva were deposited on its nostrils, and it appeared that but one fly was engaged in the business that day. The rest of tht flock had hidden near a fallen tree in the pasture, thrusting their noses close to the space between the tree and the soil, or were lying in fence corners with their noses under the lowest rail, or huddled together with their noses buried in each other's fleeces. This is the method by which the fly deposits its living eggs, or newly born living young, upon its host, the un- happy sheep. The fly is shown at flg. 18 (a); its larva fully grown at (b), the hooks by which the gi'ub draws itself up the nostril and attaches itself to the membrane lining the cavity of the skull are shown at (c), and at fig. 21 is shown the part of the skull in which the grub passes fully three-fourths of the year, emerging when fully grown and falling to the ground into which it burrows a little space, and remains until the warm weather, when it begins active business in reproducing its race. Doubtless the greater number of these grubs perish in the interval between emerging from the sheep and completing the final transformation into the flj^-, falling a prey to moles, birds, and carnivorous beetles; but sufficient number escape to continue the race and make the sheep's summer life, otherwise happy, a miserable one. The parasite seems to do little real harm to the sheep except to torment it, unless they are quite numerous, when the irritation seems to cause so much restlessness that the sheep do not thrive, but remain poor. The effect of numbers of the grubs is to
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectsheep, bookyear1900
