snakes to blend into their environment. The shape and number of scales on the head, back, and belly are often characteristic and used for taxonomic purposes. Scales are named mainly according to their positions on the body. In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing these to be counted without the need for dissection. Molting Molting (or "ecdysis") serves a number of purposes. It allows old, worn skin to be replaced and it can remove parasites such as mites and ticks that live in the skin. It's also been observed in snakes that molting can be synced to mating cycles. Shedding skin can release pheromones and revitalize color and patterns of the skin to increase attraction of mates. Renewal of the skin by molting supposedly allows growth in some animals such as insects, but this has been disputed in the case of snakes. Molting occurs periodically throughout the life of a snake. Before each molt, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the snake's eyes turn cloudy or blue-colored. The inner surface of the old skin liquefies, causing it to separate from the new skin beneath it. After a few days, the eyes become clear and the snake "crawls" out of its old skin, which splits close to the snake's mouth. The snake rubs its body against rough surfaces to aid in the shedding of its old skin. In many cases, the cast skin peels backward over the body from head to tail in one piece, like pulling a sock off inside-out, revealing a new, larger, brighter layer of skin which has formed underneath. A young snake that is still growing may shed its skin up to four times a year, but an older snake may shed only once or twice a year. The discarded skin carries a perfect imprint of the scale pattern, so it is usually possible to identify the snake from the cast skin if it is reasonably intact. This periodic renewal has led to the snake being a symbol of healing and medicine, as pictured in the Rod of Asclepius. Scale counts can sometimes be used to identify the sex of a snake when the species is not distinctly sexually dimorphic. A probe is fully inserted into the cloaca,