Fig. 846.—Foot of fly, magnified.
Fig. 847.—Compound eye. 1. Perpendicular section; 2. Surface.
Insects swarm in innumerable companies, and no one who has not seen the locusts descending upon the earth can form more than a faint idea of the devastation they occasion in an incredibly short time. These, as well as thousands of other insects, exist in myriads, and we must content ourselves, on this occasion, by merely noting the different orders and their characteristics, after we have mentioned some of the attributes common to all.
The term “insect” means cut into or divided, and so the insecta are divided, as already mentioned, into three parts,—head, thorax, and abdomen,—the thorax being subdivided into three rings, pro-thorax, meso-thorax, and meta-thorax—beginning, middle, and end. All insects have six legs, and usually two or four wings, though some have no wings at all. The legs are united to the thorax, the antennæ and eyes to the head. The abdomen contains the important sexual organs, a sting or defensive weapon, and in females the egg chamber.
Insects breathe by tubes in the sides, and consume a great quantity of air. Their powers of flying and leaping are too familiar to need dwelling upon. The wings display beautiful colours like those observable in the soap-bubble, others are covered with scales or hairs. The mouths vary very much with the species, as the manner of obtaining food is by suction or gnawing. The blood of insects is pale and thin.
The various transformations which insects undergo are always a subject of interest for the young student. The ugly forms which develop in beautiful creations are more astonishing than the change of the “ugly duckling” into the graceful swan.
Fig. 848.—Larva.
