Eyes: The eyes of a spider are usually near the front or anterior end of the head, but some are directly on top. They are single facets, hence are called simple eyes. They may number two, four, six, or eight; eight is the usual number. However, the cave spiders lack eyes entirely. Regardless of the number, the eyes are always placed in a definite arrangement. Often some pairs are much larger than others.
A typical insect is characterized by three divisions to the body—the head, the thorax, and the abdomen. Attached to the thorax are six jointed legs, three on each side, and sometimes wings.
Eyes: The eyes, when present, are placed somewhere upon the head and are of two types: simple eyes, called ocelli, which are found in insect larvae and in many adults; and compound eyes, which are found in adult insects and in the immature stages of types which resemble the adult during growth. |
