Fig. 1.—Head of an Insect
If we take an insect, and turn it over, and examine it carefully, the first thing that strikes us is that it is divided into three parts: the head; the thorax, or chest; and the abdomen, or stomach.
The head ([Fig. 1]) is a kind of box, formed of a single piece, having here and there joints more or less strongly marked, sometimes scarcely visible. It is furnished in front with an opening—often very small—which is the mouth; and with some for the eyes, and with others for the insertion of the antennæ or horns.
The integuments of the head are generally harder than the other parts of the body. It is necessary that this should be so. Insects often live and die in the midst of substances which offer some resistance. It is necessary, therefore, that the head should be strong enough to overcome such resistance. The head contains the masticatory organs, which, frequently having to attack hard substances, must be strongly supported. The exception to this rule is among insects which live by suction.
Fig. 2.—A Compound Cornea
It would be out of place here to mention the numerous modifi cations of the head which are presented in the immense class of insects.