Sometimes the tunnel runs just under the bark, and sometimes it goes straight towards the centre of the tree; and no small labour is required before it can be fully traced. Still, the result is worth the labour, for it is most interesting to trace the creature through its whole existence, from the tiny hole which it made soon after its exit from the egg, to the large aperture through which it emerged as a moth. The whole of the tunnel is strongly imbued with the peculiar and unpleasant odour which has given to the goat-moth its popular name; and the scent is so persistent, that it adheres to the fingers which have touched the sides of the tunnel, and can scarcely be removed even by repeated washings. The moth itself is a well-known insect, though rarely seen except by night. It is large, brown, round bodied; the wings are covered with a soft and downy clothing, which strongly reminds the observer of the plumage of an owl.] A wood-boring caterpillar, of a species of moth much rarer than the preceding (_Ægeria asiliformis_, Stephens), exhibits great ingenuity in constructing a cell for its metamorphosis. We observed above a dozen of them during this summer (1829) in the trunk of a poplar, one side of which had been stripped of its bark. It was this portion of the trunk which all the caterpillars selected for their final retreat, not one having been observed where the tree was covered with bark. The ingenuity of the little architect consisted in scooping its cell almost to the very surface of the wood, leaving only an exterior covering of unbroken wood, as thin as writing-paper. Previous, therefore, to the chrysalis making its way through this feeble barrier, it could not have been suspected that an insect was lodged under the smooth wood. We observed more than one of these in the act of breaking through this covering, within which there is, besides, a round moveable lid of a sort of brown wax. (J. R.) [Illustration: Larva of Ægeria.] Another architect caterpillar, frequently to be met with in July on the leaves of the willow and the poplar, is, in the fly-state, called the puss-moth (_Cerura vinula_). The caterpillar is produced from brown-coloured shining eggs, about the size of a pin's head, which are deposited--one, two, or more together--on the upper surface of a leaf. In the course of six or eight weeks (during which time it casts its skin thrice) it arrives at its full growth, when it is about as thick, and nearly as long, as a man's thumb, and begins to prepare a structure in which the pupa may sleep securely during the winter. As we have, oftener than once, seen this little architect at work, from the foundation till the completion of its edifice, we are thereby enabled to give the details of the process. [Illustration: Eggs of the Puss-Moth.] [Illustration: Rudiments of the Cell of the Puss-Moth.]