CATERPILLARS.—Caterpillars and pupæ, if not obtainable in local woods, fields, and gardens, can be had from Messrs Watkins & Doncaster, 36 Strand, London, and others. CADDIS LARVÆ.—Caddis worms are to be found in almost every stream, pond, and ditch. Most of them are vegetable feeders: therefore a plentiful supply of water weeds should be placed in their tank. Carnivorous caddis worms may be fed on small pieces of raw meat. (See Stickle-backs.) STICKLE-BACKS.—Stickle-backs are common in canals and streams. They are easily caught with the net. They should be fed once a day on grated biscuit, and occasionally on raw meat. The meat should be chopped very fine, and then pressed through a piece of perforated zinc. Very little food suffices. If too much is put in, the residue should be removed by means of a glass tube, as described in Lesson IX., p. 56. If no green water plants are obtainable, the water should be changed at least every second day by means of a siphon. Once a month is quite often enough if sufficient green plants are kept in the tank and decaying matter carefully removed. Do not over-stock—few fishes and much water is the rule. WATER PLANTS.—It is best to take the water plants which are found growing locally. The following are fairly common:—_Elodea canadensis_, water millfoil; _Potamogeton_ (_nitens_, _crispus_, or _filiformis_), “water soldier”; _Vallisneria spiralis_, _Chara_, _Nitella_, water star-wort and watercress. A good selection of excellent aquarium plants are advertised at a cheap rate by the Solway Fishery Co., Dumfries. Water plants, if not rooted in the tank, should be renewed occasionally. LARVÆ CAGE.—Take four square pieces (about 1½ inches square) of wood, each a foot long, and nail or screw them upright into the four corners of a square piece of ¾-inch deal measuring a foot each way. Stretch mosquito netting over sides, end, and top, arranging that one side can be opened. This can be managed by fastening the last fold of netting to one of the upright posts by three drawing-pins. Fresh leaves should be supplied daily. For those caterpillars which pupate in the soil, a shallow earthenware flower-pot—known in the trade as a “seed-pan”—should be supplied. The seed-pan should be filled with soil, the pupæ placed on the surface, and a layer of moss placed over them. Once a week the moss should be dipped in water, squeezed almost dry, and replaced on the pupæ. AQUARIUM.—Procure from a local florist or seedsman what is known as a “propagating bell.” These cost from 1s. up to 2s. 6d. A block of wood 12 inches square and 4 or 5 inches in thickness is also required. Bore a hole about 2 inches in diameter right through the centre of the block, to hold the knob of the bell. Then, with a gouge chisel, make a saucer-shaped hollow round the hole, to roughly fit the rounded end of the bell. Before fitting the bell into the block, interpose a thin layer of moss.