By voluntary effort on the part of the queen, each egg, as it passes this vesicle, may be touched with a most minute drop of the fluid just mentioned. Then this very marvellous fact results. An egg thus fertilised develops into a queen or a worker, according to the conditions under which it is hatched; while those eggs which are not brought in their passage into contact with the fluid, and receive no spermatozoa, become drones. Herein lies the explanation of fertile workers giving birth to drones only, and of queens, hatched after the drones of a season are dead, also laying eggs which will develop only into male bees. We are absolutely unable to account for these most extraordinary circumstances, which open up interesting fields for future investigation. Not the least wonderful point is the exercise of will, on the part of the queen, in the production of the particular kind of egg which, without making mistakes, she lays in the cells specially provided for the three classes of her offspring. The last of the abdominal organs we have now to describe, is one which is not essential to the life of the individual, but has been conferred by the Creator as a means of offence and defence, viz., the sting. Those who have frequently felt its effects have no need to be told how formidable a weapon it is; but few probably are fully acquainted with the structures which give it such potent force. If a bee be irritated, and made to thrust out its sting, we observe a dark brown and sharply-pointed dart. This, when magnified, is seen to be the sheath, in which the true sting lies and is moved. The sheath is divided down the centre, and between the two parts the real piercers work, though the sheath itself is thrust into the wound. It consists of two horny scales, smooth and closely adherent to the true darts. These last are stiff filaments, barbed along their outer edge. They are not quite equal in length, so that the teeth of the one do not lie exactly opposite those of the other. They work side by side, and, possibly with alternate motion, pierce deeper and deeper into the punctured material. The teeth give a firm hold to the imbedded weapon, and prevent its easy withdrawal. In fact, when plunged into human flesh, or into thick leather gloves, these barbs hold so tightly that the insect is unable to free itself, and if forcibly detached, or if by a vigorous effort it escapes, the sting is left behind, and frequently attached to it are portions of the viscera. The bee thus loses its life, and the injury it inflicts is the more severe. [Illustration: Fig. 40.--Sting of a Bee, greatly magnified.]