When a snake throws off its skin, which it always does once in a year, and sometimes oftener, the eyelids are thrown off with it, and a pair of new ones are found lying below all ready to take their place. Just while this is happening (and it may take a day or two) the creature is trying to look through a double layer of eye-coverings, and can see very poorly until the outer one slips off. This is the explanation of the popular saying that snakes are blind in August (the usual skin-changing time). HARMLESS SNAKES All serpents may properly enough be divided into two sections--the non-poisonous ones, which are "harmless," so far as their bite is concerned; and the poisonous ones, which inject a more or less deadly venom into wounds made by certain long weapon-teeth called fangs. Let us consider first, for a moment, the harmless ones. The great majority of them--of the common snakes of the whole world--belong to a single family called colubers; and this family far outnumbers all other serpents. Most of its members are of small size; few exceed two yards in length, one of the exceptions being our handsome king-snake of Texas and westward, which is a variety of the northern milk-snake. All are slender, agile, sometimes remarkably swift, with small heads, tapering and unarmed tails, and little or no means of defence, although some of them make such a show of fighting that they terrify many an enemy into leaving them alone. To this great family belong our various blacksnakes, or blue racers, which occasionally are more than six feet long, and are among the worst robbers of birds' nests, eating both eggs and young, and the mother bird as well if it is small, and is not quick enough in seeking to escape. This is the snake about which stories of so-called _fascination_ are told; we do not think there is much truth in them, but that the bird is simply reckless in her efforts to drive away the robber, and flies too near its darting jaws. The blacksnakes are exceedingly swift runners and agile climbers. Another excellent climber is the slender greensnake, which is so near the color of the leaves that it will not be noticed easily as it hangs in loops upon the branches of a bush, waiting quietly for some insect to come within reach. Most of our snakes, however, spend their time mainly on the ground, searching about the grass, among the tussocks of a swamp, or amid dense thickets, after frogs, toads, tadpoles, ground-nesting birds, mice, and especially insects, which last form the principal food of the smaller kinds. Among these probably the most often seen are the striped garter-snakes which abound in meadows and about haystacks and old barns, where they search holes and corners for mice and beetles. The warm, soft soil of old barnyards is a favorite place for the laying of their eggs by snakes, most of which bury them in such places and leave them to be hatched by the warmth of the sunshine.