On the right hand of the Icarian nest may be seen a singular-looking structure pendent at the end of a long footstalk. This is the nest of an insect called _Mischocyttarus labiatus_, one of the Polistidæ. In this case, the cells are built so as to be defended from the rain by a sort of penthouse, over which all the rain-drops would run, and so fall harmless to the ground. The cells of this insect are soft in texture, and are more cylindrical than angular, the angles being but very slightly marked. Here, however, is the nest of an insect called _Raphigaster Guiniensis_, which is built in a manner similar to that of the Icaria, the cells being closely in contact with each other. The material of which they are made is peculiarly soft. something like very thin and flimsy grey paper. Consequently, they must press strongly upon each other, and we might reasonably expect to find that their angles are well and boldly developed. But, instead of that, we find that they have no angles at all, but remain smooth and rounded throughout their length. [Illustration] Perhaps the most powerful argument against the equal pressure theory is to be found in the nest of a species of Icaria, which is shown in the accompanying illustration. [Illustration] As may be seen by reference to the illustration, the material of which they are made is so soft, that they bend over by their own weight, and therefore we might expect to find that they would follow the shape of the Raphigaster and the Mischocyttarus. But, we find that all the cells are boldly angular, and that the angles are just as sharp on the exterior of each cell as on the sides which cement the cells together. It is clear that the bold lines and decided angles of these cells cannot have been produced mechanically, and that they must have been intentionally formed by the insect architect. One single cell, such as is here shown, is sufficient to overthrow the theory of "equal pressure," by which insects were deprived of all mechanical skill, and supposed to labour like so many animated machines, without caring or knowing anything about the work on which they were engaged. According to the equal pressure theory, each of these cells would have required six similar cells around it before it could have assumed the hexagonal form, and yet we find that a cell which is only connected with its neighbour by one side, has its other five sides angular, and with the angles boldly defined.] _CHAPTER VIII._ LEAF-ROLLING CATERPILLARS.