"These bots, as is also the case with two or three other species, pass the autumn, winter, and spring months in the stomach, and arrive about the commencement or middle of the summer at their full growth, requiring a twelvemonth fully to complete their structure." "ON THE ŒSTRUS HEMORRHOIDALIS, OR FUNDAMENT BOT. "The part chosen by this insect for this purpose is the lips of the horse, which is very distressing to the animal from the excessive titillation it occasions; for he immediately after rubs his mouth against the ground, his fore legs, or sometimes against a tree, with great emotion; till the animal at length finding this mode of defense insufficient, enraged he quits the spot, and endeavors to avoid it by galloping away to a distant part of the field; and if the fly still continues to follow and tease him, his last resource is in the water, where the œstrus never is observed to pursue him. These flies appear sometimes to hide themselves in the grass; and as the horse stoops to graze, they dart on the mouth or lips, and are always observed to poise themselves during a few seconds in the air, while the egg is preparing on the extended point of the abdomen. [Illustration: THE ŒSTRUS HEMORRHOIDALIS. Copied from the Work by Bracy Clark, Esq. 1. The female fly about to deposit an egg. 2. The egg, magnified. 3. The bot. 4. The chrysalis. 5. The male fly. ] "When several of these flies are confined in a close place, they have a particularly strong, musty smell; and I have observed both sheep and horses, when teased by them, to look into the grass and smell it very anxiously; and if they by these means discover the fly, they immediately turn aside and hasten to a distant part of the field. "I once saw in a meadow or field upon the cliffs at Margate, a fly of this sort teasing a horse that was confined to a small space by a spike stuck in the ground, to which a cord was tied. He could not get away from its attack, and became quite furious, for in kicking at the fly with his fore foot, which he did vehemently, he often struck the bone of the lower jaw, creating excessive pain; for in that direction while grazing, the fly comes to the beard of the lower lip. "The eggs of this species are difficult to be seen upon the horse's skin or beard, owing to the agitation of the beast, and from the color of the egg being dark like that of the skin of the horse. The animal has been generally too impatient, while undergoing this operation, to let me examine them very well. I ascertained, however, its form by pressing one of these eggs from the abdomen. "The larva or grub of this species inhabits the stomach as the former, generally adhering to the white lining, and is disposed promiscuously in dense clusters, after the same manner; they may, however, be distinguished from them by being in general smaller and longer in proportion to their bulk.