generally be found resting on the wood from which they were disclosed. The grubs are destitute of feet, pale, folded, somewhat hairy, convex above, and divided into thirteen segments. Their head is large and convex.[BP] [Illustration: Magnified Cells of Pyralis strigulalis? _a._ The walls before they are joined. _b._ Walls joined, but not closed at top. _c._ Side view of structure complete.] It would not be easy to find a more striking example of ingenuity than occurs in a small caterpillar which may be found in May, on the oak, and is supposed by Kirby and Spence to be that of the _Pyralis strigulalis_. It is of a whitish-yellow colour, tinged with a shade of carnation, and studded with tufts of red hairs on each segment, and two brown spots behind the head. It has fourteen feet, and the upper part of its body is much flatter than is common in caterpillars. When this ingenious little insect begins to form its cell, it selects a smooth young branch of the oak, near an offgoing of the branchlets whose angle may afford it some protection. It then measures out, with its body for a rule, the space destined for its structure, the basement of which is of a triangular form, with the apex at the lower end. The building itself is composed of small, rectangular, strap-shaped pieces of the outer bark of the branch cut out from the immediate vicinity; the insect indeed never travels further for materials than the length of its own body. Upon the two longest sides of the triangular base it builds uniform walls, also of a triangular shape, and both gradually diverging from each other as they increase in height. These are formed with so much mathematical precision, that they fit exactly when they are afterwards brought into contact. As soon as the little architect has completed these walls, which resemble very much the feathers of an arrow, it proceeds to draw them together in a manner similar to that which the leaf-rolling caterpillars employ in constructing their abodes, by pulling them with silken cords till they bend and converge. Even when the two longest sides are thus joined, there is an opening left at the upper end, which is united in a similar manner. When the whole is finished, it requires close inspection to distinguish it from the branch, being formed of the same materials, and having consequently the same colour and gloss. Concealment, indeed, may be supposed, with some justice, to be the final object of the insect in producing this appearance, the same principle being extensively exemplified in numerous other instances. _CHAPTER XI._ EARTH-MASON CATERPILLARS.