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.
First, it must be noted that the bee has nothing strictly analogous to our lungs, heart, liver, and other structures making up a true circulating-system. At the same time there is a real oxygenation of the fluids of the body, with a consequent evolution of heat, water, and carbonic acid gas.
The breathing apparatus has not its aperture for inspiration and expiration situated in the head, as is the case in the higher animals; but air is admitted and expelled through apertures along both sides of the body. In the thorax are two pairs of such openings, and there is a pair on each ring of the abdomen. These air-holes are called spiracles, or stigmata, and lead into two minute chambers, one behind the other, the outer being provided with a number of short hairs, to prevent the entry of foreign particles likely to obstruct the important passages.
Fig. 32.—Abdomen of Bee, Showing Respiratory Organs.
a, Air-sac. b b b, Spiracles.