There are three distinctly separated divisions of the insect body--head, thorax, and abdomen--each consisting of a varying number of segments (Fig. 3). The head segments are so closely fused as to be practically untraceable, the cuticle forming a rigid capsule; the thorax, to which the head is attached, carries the wings (when present) and the legs, and consists of three segments; posterior to the thorax is the abdomen, comprised of several segments, which show the typical segmentation of insects better than any other part of the body. The head capsule is more or less freely movable on the thorax, and bears certain sensory organs, together with the mouth appendages. The sensory organs are the eyes and the feelers, or antennæ. On each side is a compound eye of varying size, according to the insect; each eye consists of a variable number (from a comparative few to several thousand) of microscopic, hexagonal lenses, each of which records a separate image. Between the compound eyes, on top of the head, are three simple eyes in some insects, but in others one or all of these may be absent. Between the compound eyes on the front aspect of the head is a pair of feelers, or antennæ; they consist of a variable number of joints, are freely movable and highly sensory, thread-like or hair-like, short, or longer even than the whole body, and may be bare or clothed to a varying degree with hair or bristles. On the antennæ are the organs of touch, smell, and sometimes hearing. [Illustration: FIG. 3.] When the head of a weta, grasshopper, or cockroach is removed from the body and boiled for a few minutes in a 10 per cent. solution of caustic potash, and then washed in water in order to remove the muscles and other tissues, a large opening will be seen on the posterior surface where the head was attached to the thorax; also, if the mouth appendages are pulled apart, they will be seen to surround another opening on the lower aspect of the head capsule, marking the position of the mouth. The digestive canal passes from the mouth through the posterior opening into the thorax.