Crawling around

As my caterpillar is getting bigger, he seems to move around a little more. Most of the time he just sits in one spot eating, but today he seemed especially active. One of the things I have noticed about his legs is that there are gaps between sections of legs. There are three groups of legs--the front set of six legs look more like feelers, the next two sets of legs (eight and two legs, respectively) seem to be more solid and leg like. It almost seems like he has some sort of suction cups on them as he is able to cling to the sides of the cup or even on the top of the cup. I wanted to learn how he can cling to the walls or basically any surface it seems.
According to the book A Life Cycle of Butterflies, the front legs are considered to be "true legs" while the majority of the back legs are called "prolegs". These prolegs have "rings of microscopic bristles shaped like crochet hooks" (NSRC, p. 28). These act like suction cups and help the caterpillar cling to any surface. This can all be illustrated in the following diagram: