Page:The Book of the Aquarium and Water Cabinet.djvu/128

116 it comes forth to sport in sunbeams, and, for but a brief season, lead a life of joy—

But beauty of the high poetic kind is not the inheritance of every member of the class insecta; and the water-cabinet presents us with many that have but analogical resemblances to the typical structure of the moth or the fly, though the naturalist finds beauty in a beetle, and points of profound interest in a maggot or grub.

Since larva are distributed through at least three elements, being, according to the species, inhabitants of earth, air, and water, the breathing apparatus arrests our attention, as constituting a distinct feature in the anatomy of the insect. A caterpillar may be regarded as all stomach, and the cravings of this immense digesting tube easily account for the voracity of larva of all kinds. In the larger animals, the food is elaborated into blood, and brought to the lungs to be oxygenated by means of contact with the air, but the insect does not breathe at the mouth, but at the other end, or by means of tubes arranged along the sides of the body. In a caterpillar there are usually eighteen of these tubes, the orifices of which may be seen in action. These tubes all run into two larger lateral tubes, or wind-pipes, arranged one on each side of the body; and from these lateral tubes innumerable smaller ones diverge, and convey air to the vessels in which the digested food is contained, and thus supply it with oxygen. Swammerdam was the first who