Page:Insects - Their Ways and Means of Living.djvu/42
The outside of the insect's body, instead of presenting a continuous surface like that of most animals, shows many encircling rings where the hard integument appears to be infolded, as it really is, dividing each body region except the head into a series of short overlapping sections. These
head, a thorax bearing the legs, and a terminal abdomen (Fig. 63). On the head is located a pair of long, slender antennae (Ant) and a pair of large eyes (E). Winged insects have usually two pairs of wings attached to the back of the thorax (W2, W3).
The head, besides carrying the antennae (Fig. 63, Ant), has three pairs of appendages grouped about the mouth, which serve as feeding organs and are known collectively as the mouth parts. The presence of four pairs of appendages on the head raises the question, then, as to why the head is not segmented like the thorax and the abdomen. At an early stage of embryonic growth the head is segmented, and each pair of its appendages is borne by a single segment, but the head segments are later condensed