§ III. THE THORAX AND ORGANS OF MOTION.
The thorax or chest approaches in figure to a sphere, and is united to the head by a thread-like ligament. This is the centre of the organs of motion. Here are attached both the muscles that move the legs and wings, and the legs and wings themselves.
In Fig. 1 of [Plate II.], b, b, b show the muscles that move the wings; e, e, the bases of the wings. These appendages consist of two pairs of unequal size, which are arranged to hook together. In [Plate I. Fig. A] will be seen the margins of the two wings. In [Fig. B] are the eighteen or twenty hooks placed on the anterior margin of the hinder wing, whilst the posterior margin of the fore wing is beautifully folded over to receive them, so that, when employed in fanning for ventilation, the two wings on each side act as one, and present an unbroken surface to the air. The wings of workers are larger than those of the queen, but those of drones are much larger still.
The bee has six legs, three on each side. Each leg is composed of several joints, having articulations like a man's arm, for the thigh, the leg, and the foot. The foremost pair of these are the shortest; the middle pair are somewhat longer, and with them the bee unloads the little pellets from the baskets on her thighs; the hindmost are the longest of all. On the outside of the middle joint of these last there is, in each leg, a small cavity, in the form of a marrow-spoon, called the "pollen basket." The pollen is conveyed from the front to the second pair of legs, and from these to the receptacles in the hind ones. Fig. 2 b in [Plate I.] shows the inner side of the hind leg and pollen brush; 2 b*, the outer side and pollen basket. On entering a flower a bee often covers itself with pollen, and hence the need for the brash apparatus on reaching home.
The legs are covered with hairs, more particularly the edges of the cavity mentioned, in which the kneaded pollen requires to be maintained securely. In this they convey those coloured loads which are so constantly seen carried into a hive. This basket, or pollen groove, in the thigh is peculiar to the worker; neither queen nor drone has anything of the kind.
Another provision of the bee's limbs consists in a pair of hook's attached to each foot, with their points opposite to each other, by means of which the bees suspend themselves from the roof or sides of hives, and cling to each other as they do at swarming time or prior to and during the formation of new comb, thus forming a living curtain. In these circumstances each bee, with its two fore claws, takes hold of the two hinder legs of the one next above. This mode of suspension seems agreeable to them, although the uppermost in the festoon appear to be dragged by the weight below. Wildman supposed that bees had a power of distending themselves with air to acquire buoyancy, and thus lessen the burden of those at the top. They find no difficulty in extricating themselves from the mass; the most central of the group can make its way without endangering the stability of the grape-like cluster.
Bees are able to walk freely in an inverted position, either on glass or other slippery substances. The peculiar mechanism of their feet, which enables them to do so, consists in their having in the middle of each hook a thin membranous little cup or sucker that is alternately exhausted and filled with air. Flies have the same beautiful apparatus—hence a fly commonly selects the ceiling for a resting-place. These little air-cups, or exhausted receivers, may be seen by applying a strong magnifying-glass to a window that has a bee traversing the reverse side. The edges of these little suckers are serrated, so as to close against any kind of surface to which their legs may be applied. This apparatus may be also serviceable for gathering the pollen before transmitting it to the baskets on the hind legs. Besides these appendages and apparatus of the thorax, that region is traversed by the œsophagus or gullet (the opening to which will be found in [Plate I. Fig. 2 c]), on its way to the digestive and other organs, situate in the third part of the insect—viz., the abdomen. The covering of the thorax, with the external covering of the gullet, may be seen in the drawing of the magnified dissected body of the bee ([Plate II. Fig. 1]).
The breathing apparatus of bees is a very remarkable feature: they have no lungs, but, instead, air-vessels, or tubes and bladders ramifying through every part of the frame. The external openings of these, which are called "spiracles," are found in the sides of their bodies behind the wings. Two pairs of them are located in the thorax, and one pair on each side of the scales of the abdomen. They would be difficult to show in a drawing, as the multitude of hairs which protect them are in the way of getting at a very distinct delineation. The writer has traced their oval form by the aid of Messrs. R. and J. Beck's "Binocular Microscope," and exceedingly interesting objects they appeared. From the circumstance of bees breathing through these orifices in their bodies, it will not be difficult to understand how sadly the little creatures must be inconvenienced when by accident they fall on loose mould, and thus have their breathing pores choked with dust; it also shows how needful it is to prevent bees being besmeared with honey (by using bad appliances for feeding), which is still more injurious to them. The air-vessels are all that they possess of a circulating system, as bees have neither lungs, heart, liver, nor blood. It appears, however, that a white fluid matter, called "chyle," which in degree answers the purpose of blood, is produced in the intestines, nourishes the body, receives the oxygen from the air-vessels, and generates that animal warmth so necessary for the insect's well-being—warmth which, as a matter of course, say Schmid and Kleine in their "Leading Threads," settles that it is incorrect to call the insect a cold-blooded animal. Bees have the power of counteracting superabundant heat by perspiration. Not unfrequently, on a hot summer's morning, a good deal of moisture may be noticed at the entrance of a crowded hive, which the inmates have been enabled to throw off. This is a healthy sign, because a sign of great numerical strength. The humming sound always to be heard in a beehive is produced by breathing.