How well I remember the "whack! whack! whack!" from the inside of the pasteboard or wooden box as I entered the room, or chanced to make the slightest commotion in its neighborhood, as the captive pets threatened to dash their brains out in their demonstrations at my approach. Opening the box, I was always greeted with the same concert of whisking heads, the action being more particularly expressive from the long projecting lash of hairs, an inch and a quarter in length, with which the caterpillar's head was provided. One singular feature of these hairs had always puzzled me in the earlier life of the caterpillar, but was soon explained by close observation. At intervals of every quarter of an inch or so in the length of the slender tuft we find, in perfect specimens, a tiny brown speck--perhaps three or four--graduating in size to the tip of the hairs, where the atom is scarcely visible, or generally absent. A careful examination of their shape revealed the fact that they were exactly like the heads of the younger caterpillars in all their stages, and their presence and successive accumulation were readily explained by the moulting habits of the caterpillar, which is common to all caterpillars. By these telltale tokens we know that the professor has changed his clothes--let us see, one, two, three, four--perhaps five times. When he first emerged from the egg on the lilac-leaf he was indeed a tiny atom; his head would make a small show laid upon our page. When about a week old, by dint of a good appetite and voracious feeding, he had managed to "outgrow his skin," as it were. He could literally hold no more, and realizing that nature would come to his relief, he began to spin a tiny web upon the leaf-stalk in which to secure his hooked feet for a temporary rest, sleeping off his dinner, as it were.