Round Mount Alburnus, green with shady oaks, And in the groves of Silarus, there flies An insect pest (named _Oestrus_ by the Greeks, By us _Asilus_): fierce with jarring hum It drives, pursuing, the affrighted herd From glade to glade; the air, the woods, the banks Of the dried river echo their loud bellowing. Had we not other instances to adduce, of similar terror caused among sheep, deer, and horses, by insects of the same genus, which are ascertained not to penetrate the skin, we should not have hesitated to conclude that Vallisnieri and Réaumur are right, and Mr. Bracey Clark wrong. In the strictly similar instance of Reindeer-fly (_Oestrus tarandi_, Linn.), we have the high authority of Linnæus for the fact, that it lays its eggs _upon_ the skin. "I remarked," he says, "with astonishment how greatly the reindeer are incommoded in hot weather, insomuch that they cannot stand still a minute, no not a moment, without changing their posture, starting, puffing and blowing continually, and all on account of a little fly. Even though amongst a herd of perhaps five hundred reindeer, there were not above ten of those flies, every one of the herd trembled and kept pushing its neighbour about. The fly, meanwhile, was trying every means to get at them; but it no sooner touched any part of their bodies, than they made an immediate effort to shake it off. I caught one of these insects as it was flying along with its tail protruded, which had at its extremity a small linear orifice perfectly white. The tail itself consisted of four or five tubular joints, slipping into each other like a pocket spying-glass, which this fly, like others, has a power of contracting at pleasure."[GL] In another work he is still more explicit. "This well-known fly," he says, "hovers the whole day over the back of the reindeer, with its tail protruded and a little bent, upon the point of which it holds a small white egg, scarcely so large as a mustard-seed, and when it has placed itself in a perpendicular position, it drops its egg, which rolls down amongst the hair to the skin, where it is hatched by the natural heat and perspiration of the reindeer, and the grub eats its way slowly under the skin, causing a bump as large as an acorn."[GM] The male and female of the reindeer breeze-fly are figured in the 'Library of Entertaining Knowledge, Menageries,' vol. i. p. 405.