That the Sheep is liable to the attack of the gadfly, which deposits its eggs in the nostrils of the unfortunate animal, was as well known in the ancient as in modern times. It is scarcely necessary to mention that the insect in question is the _Æstrus ovis_. Instinctively aware of the presence of this insidious and dreaded enemy, which, though so apparently insignificant, is as formidable a foe as any of the beasts of prey, the Sheep display the greatest terror at the sharp, menacing sound produced by the gadfly's wings as the insect sweeps through the air towards its destination. They congregate together, placing their heads almost in contact with each other, snort and paw the ground in their terror, and use all means in their power to prevent the fly from accomplishing its purpose. When a gadfly succeeds in attaining its aim, it rapidly deposits an egg or two in the nostril, and then leaves them. The tiny eggs are soon hatched by the natural heat of the animal, and the young larvæ crawl up the nostril towards the frontal sinus. There they remain until they are full-grown, when they crawl through the nostrils, fall on the ground, burrow therein, and in the earth undergo their changes into the pupal and perfect stages. It need hardly be said that an intelligent shepherd would devote himself to the task of killing every gadfly which he could find, and, as these insects are fond of basking on sunny rocks or tree-trunks, this is no very difficult matter. The Rabbinical writers, however, being totally ignorant of practical entomology, do not seem to have recognised the insect until it had reached its full larval growth. They say that the rams manage to shake the grubs out of their nostrils by butting at one another in mimic warfare, and that the ewes, which are hornless, and are therefore incapable of relieving themselves by such means, ought to be supplied with plants which will make them sneeze, so that they may shake out the grubs by the convulsive jerkings of the head caused by inhaling the irritating substance. The same writers also recommend that the rams should be furnished with strong leathern collars. When the flock is on the march, the rams always go in the van, and, being instinctively afraid of their ancient enemy the wolf, they continually raise their heads and look about them. This line of conduct irritates the wolves, who attack the foremost rams and seize them by the throat. If, therefore, a piece of stout leather be fastened round the ram's neck, the wolf is baffled, and runs off in sullen despair.