Three general methods are employed by fossorial Hymenoptera to construct the dwelling in which metamorphosis is to take place. Some hollow burrows at a great depth under a shelter, and then the cocoon consists of a single wrapper, so thin as to be transparent. Such is the case with Philanthidæ and Cerceris. Others are content with a shallow burrow in open ground; but in that case they have silk enough for manifold wrappings of the cocoon, as with Sphegidæ, Ammophila, and Scolia; or if the quantity be insufficient, they use agglutinated sand—as, for instance, the Bembex and Palarus. One might take a Bembex cocoon for a solid kernel, so compact and resistant is it. The form is cylindrical—one end rounded, the other pointed. The length is about two centimetres. Outside it is slightly wrinkled and coarse, but within the walls are smoothed by a fine varnish. Rearing at home has enabled me to follow every detail of the construction of this curious piece of architecture—a real strong box which can brave all the severity of the weather. First of all the larva pushes away the remains of its feast into a corner of the cell, or the compartment arranged for it in a box with paper partitions. Having cleared a space, it affixes to the walls of its abode threads of a beautiful white silk, forming a spidery web which keeps the heap of food-remains at a distance, and serves as scaffolding for the work to come. This work consists of a hammock, suspended far from anything that can defile it, in the centre of threads stretched from wall to wall. Fine, beautiful white silk is the only material used. The shape is that of a sack open at one end, with a wide circular orifice, closed at the other and ending in a point; a fisherman’s basket gives a very fair idea of it. Then the edges of the aperture are permanently kept apart by numerous threads fastened to the neighbouring walls. The tissue of the bag is extremely fine, allowing all that the grub does to be seen.