We can readily understand the importance to these insects of having their organs of flight powerful, and yet not weighty, tough without being clumsy. Considering the length of their daily journeys, and the constant and rapid movements they require to make, we easily discern how well suited to their needs is the structure of their wings. But we must call attention to a remarkable provision for the further utility of these organs. Under a lens of medium power may be seen, along the anterior edges of the hind wings, a series of booklets of hair, while on the posterior edge of the front wings is a rib, or bar, which the booklets can grasp. By this means the two wings, when used for flight, become practically one, thus presenting unbroken resistance to the air, and, in consequence, greatly increasing the power of propelling the body. When at rest, the unhooking of the edges enables the wings to be folded out of the way--no mean advantage in the crowded hive. [Illustration: Fig. 31.--Hooklets of a Bee's Wing.] But there is a further benefit thus conferred on the insect. During hot weather, and when the population is very dense, ventilation is constantly and vigorously carried on by the workers, who, fixing themselves firmly by their claws to the floor-board at the entrance, some outside and some just within their homes, direct numerous currents of air into the hive. Of course there must issue a quantity corresponding to what is driven in, and thus a perpetual and free circulation is kept up. Now, if the wings worked independently, not only would a smaller quantity of air be affected by each stroke, but the two sets of motions would, to some extent, counteract each other. As it is, the hooked wings act like well-constructed and well-used fans. By the simple experiment of slitting such an implement down the middle, the comparative advantages of a broken and an unbroken surface, for fanning purposes, can easily be put to the proof. Thus, again, we are struck with the fact that the more closely we examine the organs of any segment of the body of the insect, the more reason do we find to admire the skill, and the care for His creatures, manifested by the infinitely wise and the infinitely good Maker of them all. Beauty, adaptation, perfection, are the words which are continually suggested to our minds by the contemplation of the structure of the bee. CHAPTER XIV. THE ABDOMEN. Respiratory Organs--Circulation of Nutritive Fluid--Digestion and Nutrition--Secretion of Wax--Reproductive Organs--Detailed description of Sting--Effects of Poison--Queen's Sting. The abdomen constitutes the largest and hindmost segment of the body, and is important as containing several structures which have most essential functions in the economy of the insect. Among these are the chief parts of the respiratory apparatus, the digestive, the wax-making, the reproductive, and stinging organs.