It is different, however, in clear water and on land. I have seen crayfish rush down stream after bits of meat thrown to them, thus showing that here, at least, the sense of sight directed them. Again, I have enticed crayfish from clear streams by slowly dragging a baited hook in front of them. Moreover, when high and dry on land, I have seen them follow with their eyes and bodies the tempting morsel as it waved to and fro in the air above their heads. The female crayfish carries her eggs beneath her tail, and, when they have hatched out, the young find this sheltering member a safe and cosey dwelling-place until they have grown strong enough to enter life's struggle. At such times, the mother crayfish is quite brave, and will do battle with any foe. With her eyestalks protruded to their utmost extent, she vigilantly watches her enemy. Her eyes follow his movements, and her sharp nipper is held in readiness for immediate use. Actual experimentation has taught that these animals can descry a man at the distance of twenty or twenty-five feet. When approaching a crayfish "town" for the purpose of making observations, I use the utmost caution; otherwise, each inhabitant will retreat into its burrow before I can come close enough to observe them, even with my field-glasses. The gyrinus, or "whirligig beetle," whose dwelling-place during the greater portion of its life is, like that of the crayfish, in ponds and streams, has remarkably acute vision. This insect is a true cosmopolite, however, and is as much at home on dry land as it is in the water. All seasons seem to be alike to it, just so the sun shines; for, during the hottest days of summer and the coldest days of winter (that is, if there is sunlight and no ice on the water), it may be seen on the surface of ponds and streams, gyrating hither and thither in a seemingly mad and purposeless manner. Several of these creatures will be seen at one moment floating on the water, still and motionless; the next moment they will be darting here and there over the surface of the water, their black and burnished backs shining in the sunlight like brilliant gems. Suddenly, it is "heels up and heads down," and they disappear beneath the surface, each of them carrying a bubble of air caught beneath the wing-tips; or, as the late William Hamilton Gibson expresses it, "they carry a brilliant lantern that goes gleaming like a silver streak down into the depths, for a bubble of air is caught beneath their black wing-covers, and a diamond of pure sunlight accompanies their course down among the weeds until they once more ascend to the surface."[14] This little beetle is well provided with eyes, for it has a large pair beneath its head, with which it sees all that is going on in the water below, and another pair on the sides of its head, with which it keeps a bright lookout above. That it has remarkably keen vision with the latter pair, any one who has tried to steal upon them unawares can testify.[15]