The connecting medium might even have permitted a common current of nutriment, contributed to by each individual, to circulate through the whole compound body. But how little of anything essential to the animal would be affected by cutting through this hypothetical connecting and vascular integument, and setting each individual free! *

(902). In all the great class of Insects, the blood is equably diffused through the visceral cavity, and is contained in the spaces intervening between the muscles, nerves, tegumentary organs, etc, and in the still smaller lacunae that exist between the fibres or constituent lamellae of the various organic tissues. The fluid thus diffused is characterized by the presence of globules or corpuscles of determinate shape; and in most cases it is easy to ascertain by means of the microscope that the circulation is carried on in a system of irregular cavities, much in the same way as the blood of vertebrate animals is in the vascular system with which they are furnished.

* Loc. cit. p. 61.

(903). Innumerable are the means employed by nature to keep the balance between the increase and destruction of the insect tribes; and countless enemies are provided for the purpose of checking their inordinate accumulation.

The Hive Bee (Apis mellifica.) A, Working Bee. B, fertile female, or Queen Bee.

Fig. 173. The Hive Bee (Apis mellifica.) A, Working Bee. B, fertile female, or Queen Bee.

C, the male, or Drone.

(904). Among the most remarkable provisions for preventing superabundant fertility is that law which compels the most prolific insects to live in large societies, and permits but one female out of a multitude to lay eggs. As an example of this, we may take the Hive-bees*, so remarkable for their elevated instincts and industrious habits. A swarm of bees consists, first, of females whose sexual organs remain permanently in an undeveloped condition, usually called the workers (fig. 173, a); secondly, of perfect males or drones (c); and thirdly, of a solitary fertile female, called the queen (b), which gives birth to all the progeny of the hive; and thus, instead of 20,000 or 30,000 eggs being furnished by every one of as many females, one female only is permitted to be instrumental in perpetuating the species.

(905). The Termite Ants likewise, were it not for a similar restriction, would soon, by their overwhelming increase, depopulate whole regions of the earth, and render the countries in which they are met with absolutely uninhabitable by their extreme voracity. A community of Termites is said to consist of five different classes: namely, winged males and females (fig. 174, a); apterous neuters, or soldiers, which have large heads furnished with strong projecting mandibles (b); un-winged pupae, having a smaller head, and the rudiments of wings only (c); and, lastly, of similarly-formed larvae, or workers (d), differing from the pupae only in wanting the rudiments of wings. The following is a brief history of the establishment and growth of a colony of these insects, as narrated by Burmeister *. At the termination of the hot season, the young males and females disclosed in a nest quit it, and appear upon the surface of the earth, where they swarm in innumerable hosts, and pair. The busied workers then convey a chosen male and a female back into the dwelling, and imprison them in the central royal cell, the entrances to which they decrease and guard: through these apertures the imprisoned pair then receive the nutriment they require. The male now, as amongst all other insects, speedily dies after the impregnation of the female has been effected; but the female from this period begins to swell enormously from the development of her countless eggs, and by the time she is ready to commence laying, her abdomen is about 1500 or 2000 times larger than all the rest of her body (fig. 174, e.) During the period of this swelling, the workers remove the walls of the royal apartment, uniting the nearest cells to it; so that in proportion to the increase of the body of the queen, the size of the abode she inhabits is also increased. She now commences laying eggs, and during the process the abdomen exhibits a continual undulatory motion, produced by the peristaltic movement of the egg-ducts; while the workers convey away the eggs as they are laid, and deposit them in the distant rearing-cells of their wonderful habitation. The reader will be able to form some idea of the relative proportions and outward appearance of the edifices erected by these comparatively minute beings by the group of their citadels represented in the background of the figure; but to describe them more minutely would lead us into details unconnected with our subject*.

* For ample details concerning the habits of these interesting creatures, the reader is referred to Dr. Bevan's work ' On the Honey-bee; its Natural History, Physiology, and Management.' 1 vol. 12mo. London.

Colony of Termite Ants. A, Winged male. B, Soldier. C, Wingless pupa. D, Workers. E, Queen Termite enormously distended with eggs.

Fig. 174. Colony of Termite Ants. A, Winged male. B, Soldier. C, Wingless pupa. D, Workers. E, Queen Termite enormously distended with eggs.

* Manual of Entomology, p. 535.

(906). The eggs of these little animals vary much in shape and external configuration; so that, from the beauty of their forms and exquisite sculpture, some of them are interesting objects for the microscope.

(907). We have already spoken concerning the metamorphoses which insects undergo during the progress of their development from the form under which they first leave the egg to their mature condition, when they become fertile, and, in most instances, acquire those instruments of flight so generally characteristic of their perfect state. Before entering upon a more minute inquiry concerning the physiological principles upon which the important changes in question depend, and the phenomena attending the process, it will be advisable to cite a few more examples illustrative of the most interesting varieties of metamorphosis signalized by authors. Fabricius distinguishes five different kinds of metamorphosis, and has applied a different name to each.