Few people who have lived in Madagascar can have failed to notice a small longish lump of light coloured clay stuck under the eaves of the house, or on the side of a window, or, in fact, in any sheltered place; and if we take the trouble to break off a piece, we find that this lump of clay contains a number of cells, all filled with caterpillars or spiders in a numbed and semi-lifeless condition. The maker of these cells is a black wasp about an inch long, with russet wings, and as one sits in the verandah of one’s house one may often hear a shrill buzz somewhere up in the rafters, and there the little worker is busy bringing in pellets of clay with which she builds up the walls of the cell. (When I lived at Ambòhimànga, one of these wasps made a nest with several cells in my study, as the window was generally open to the air.) Presently she is off again for another load to the banks of a little stream where she has her brick-field. Kneading the red earth with her mandibles, she quickly forms it into a pellet of clay, about the size of a pea, which she dexterously picks up and flies away back to the verandah. This pellet is placed on the layer already laid, carefully smoothed and “bonded in” with the previous structure, until a cell is completed. Observations made by a careful student of animal and insect life show that about twenty-six journeys finish one cell, and that on a fine day it takes about forty-five minutes to complete it. This is only one out of many cells, however, placed on the top of each other. With regard to the storing of these cells with food for the grubs of the wasp, Mr Cory[8] found that the number of spiders enclosed in eleven cells varied from eight to nineteen. These are caught by the wasp, stung so as to be insensible, but not killed, and then the egg is laid in their bodies, so that on being hatched the grub finds itself in the midst of food. [Sidenote: BUILDING AND BURROWING WASPS] Another species of these solitary wasps is a much larger insect, about two inches in length, and she makes nests, which are extremely hard, and are like half-buried native water-pots, with the mouths facing the observer, and arranged regularly one above the other. When finished they are plastered over with rough gravel. Unlike the wasp previously mentioned, this one does not fetch the clay for building purposes from the banks of a stream, but carries the water to the dry earth, which it then damps and kneads into balls. The cells are stocked with caterpillars, which are stung and numbed in the same way as the spiders are treated by the first-named wasp. There are usually three caterpillars placed in each cell.