The whole body of a drone is in a state of vibration when it hums. Though deprived of its wings, it is capable of producing a sound exactly similar, and probably the same with its former hum: even when the legs are cut off, the trunk retains its tremulous motion, and utters an audible noise. If immersed in water, many air-bubbles are disengaged from it: but though the mutilated insect be taken out alive, it is no longer sonorous. “This experiment, however incomplete,” says a writer in the Dictionnaire des Sciences Naturelles, “tends at least to prove, that the humming of bees is not occasioned by a strong vibration of the internal part of the upper wings, but rather by a tremulous affection of the entire body; and perhaps even by the escape of a greater quantity of air through the stigmata or spiracles. This last would amount to a sort of voice.” The humming noise with which a flower is always approached by the bee, ceases as soon as she has alighted upon it, though during the time that she is extracting its sweets she is in a constant vibratory motion.
Circulation.
The term circulation is not strictly applicable to the imperfect sanguineous system of insects, as the fluid which supplies their bodies with nutriment is not distributed to its several parts through the medium of a heart and vascular system. Lyonnet and Cuvier are both of opinion that insects have no heart, whereas all creatures that possess a circulation, properly so called, have a heart, lungs or gills, and a liver; but insects have only air-vessels and hepatic ducts. The chyle which is produced in their intestines, transpiring through the pores of the intestinal canal, passes into the general cavity of the body, where it is probably animalized, and made to answer the same purposes that blood does to creatures of a higher class, though when animalized it still retains its white colour. Although its distribution is obscure, from its analogy to blood, we may conclude that it is a fluid which visits and nourishes every part of the insect’s body; that from it secretions are made, and that, as in other creatures, it is fitted for these purposes by receiving oxygen from the air-vessels. Cuvier has observed that the blood of insects, “for want of a circulating system, not being able to seek the air, the air goes to seek the blood;” the air-vessels, as I have stated under the head of Respiration, are distributed to every part of the body.
Nutrition.
From what I have said under the head of Circulation, it will appear evident that the bodies of bees and other insects are supplied with nutriment in a very simple manner. Cuvier is of opinion that it is obtained by direct absorption or transudation, by imbibition as he calls it, through the pores of the intestinal canal, along which the blood or animalized chyle passes: and Lyonnet thinks that this imbibition is analogous to that which takes place from the earth by the roots of plants.
Secretion.
Every thing connected with the subject of secretion seems to be obscure: it is evident, however, that secretions do take place; for silk, wax, and poison are all the results of that process. The first of these substances is only secreted by the bee when in its larva state. I must refer those who wish for information respecting silk, to those naturalists who have written on the silk-worm. The secretion of wax I shall treat of hereafter in a distinct chapter; and it will be better perhaps to speak of Poison, after describing the sting and its appurtenances. There is one secretion however, on which I will say a few words in this place,—viz. Perspiration.
Perspiration.
The temperature of insects not gregarious, is generally that of the medium they inhabit; but bees possess the power not only of preserving a high temperature during the coldest mouths of winter, but of raising that temperature under particular circumstances. Dr. Darwin has observed that they generate heat by a general motion of their legs, as they hang clustered together in the hives: Huber thinks that it may be increased by the agitation of their wings;—whatever disturbs them so as to cause a tumult invariably produces a considerable accession of heat. Inch, a German, plunged a thermometer into a bee-hive in the winter, and saw the mercury stand 27 degrees higher than it did in the open air. Mr. Hunter found the heat of a hive vary from 73° to 84° of Fahrenheit; and Huber, who says that in a prosperous hive the thermometer in winter commonly stands at from 86° to 88°, and in summer between 95° and 97°, states that he has observed it, on some occasions, to rise suddenly from about 92° to above 104°. The former naturalist, about ten o’clock in the morning, in the middle of July, when the quicksilver in the thermometer in the open air ranged at 54°, found that on plunging it into a bee-hive, it rose in less than five minutes to 82°. At five the next morning it stood at 79°,—at nine it had risen to 83°,—at one to 84°; and at nine in the evening it had fallen to 78°. On the 30th of December, when the temperature of the air was 35°, that in the hive was 73°. Bees also possess the power of counteracting or throwing off superabundant heat, by perspiration. Huber observed, that when crowded together in hot weather, they become much heated, and perspire so copiously that those near the bottom seem perfectly drenched, and are for a time incapable of flying from the moisture on their wings.
Motion.