OF THE PROBOSCIS OF THE TABANUS OR OX-FLY.
Plate XVI. Fig. 1. is a microscopic view of the proboscis of a tabanus, with which it pierces the skins of horses and oxen, and nourishes itself with their blood; Fig. 2. the same of the natural size. The singular and compound structure, together with the wonderful form and exquisite beauty of this apparatus, discovers such a view of the wisdom, power, and greatness of its infinite composer, as must strike with admiration every contemplative observer, and lead him to reflect on the weakness, impotence, and nothingness of all human mechanism, when compared with the immense skill and inimitable finishing displayed in the subject before us. The whole of this formidable apparatus is composed of six parts, exclusive of the two guards or feelers a a, all of which are inclosed in a fleshy case, which in the figure is totally removed, as it contained nothing remarkably different from that of other insects with two wings. The guards or feelers a a, are of a spungy or fleshy substance, and are grey, covered with short hairs or villi; they are united to the head by a little joint of the same texture, which in this view of the object could not be shewn. These guards are a defence to the other parts of the apparatus, as they are laid upon it side by side, whenever the animal stings, and by that means preserve it from external injury. The two lancets b b and B, evidently open the wound, and are of a delicate and tender structure, formed like the dissecting knife of the anatomist, with a sharp point and slender edge, but gradually increasing to the back. The two instruments, c c and C, appear as if intended to enlarge the wound, by irritating the parts round it; to accomplish which, they are jagged or serrated; they may also serve, from their hard and horny texture, to defend the tube e E, which is of a softer nature and tubular to admit the blood, and convey it to the stomach; this delicate part is inclosed in a case d D, which entirely covers it. These parts are drawn separately at B, C, D, E. De Geer observes, that it is only the female that sucks the blood of animals; and Reaumur declares, that having made one disgorge itself, the blood it threw up, appeared to him to be more than the whole body of the insect could have contained.