On the right is shown the group of mouth-lancets belonging to one of the Humble-bee flies (_Bombylius_). These flies do not suck blood like the Mosquito, the Flea, and the Gad-fly, but they use the long proboscis for sucking the sweet juices out of flowers, and in consequence it is nearly of the same form as if it were meant for sucking blood. Indeed, there are some insects which do not seem to care very much whether the juice which they suck is animal or vegetable. [Illustration: 8 CLAW.--SHEATH OPENING ALONG THE CURVED BACK.] [Illustration: INDIAN TULWAR.--SHEATH OPENING ALONG THE CURVED BACK.] On the right hand of the illustration is seen an Indian sword, or “Tulwar,” drawn from one of my own specimens. I have selected this example on account of the structure of the sheath. It is evident, from the form of the blade, that the sword cannot be sheathed point foremost, and that therefore some other plan must be used. In this weapon the sheath is left open on one side, the two portions being held together by the straps which are shown in the figure. Of course there is loss of time in sheathing and drawing such a sword, but the peculiar shape of the blade entails a necessity for a special scabbard. On the other side is shown one of the fore-claws of a cat, which, as we all know, can be drawn back into its simple sheath between the toes, when it is not in use. This sheath is exactly the same in principle as that of the Indian tulwar, and any one can examine it by looking at the foot of a good-tempered cat. I have done so even with a chetah, which is not a subject that would generally be chosen for such a purpose. On the next illustration is shown an ordinary Lancet, in which the blade is guarded between a double sheath, the two halves and the blade itself working upon a common pivot. As for the ordinary sword and dagger sheaths, it is not worth while to figure them. * * * * * TURNING to the opposite side of the illustration, we shall see a few of the innumerable examples in which the principle of the sheath was carried out in Nature long before man came on the earth. The reader should compare this figure with the side view of the Gnat’s lancets given on p. 81. [Illustration: LANCETS OF TABANUS CLOSED.] [Illustration: LANCETS OF MOSQUITO PARTLY OPEN.] [Illustration: SURGEON’S LANCET PARTLY OPEN.] They represent the cutting and piercing instruments of several insects, all of which are very complicated, and are sheathed after the manner of the lancet. Indeed, they are popularly known as “mouth-lancets,” and with reason, as the reader may see by reference to the illustration.