In a number of the systematic studies of caddisflies with which I have been concerned, it has been necessary to rear larvae to the adult stage in the laboratory. Several methods proposed for rearing aquatic insects were considered, but these seemed open to some improvement, mainly because, for my purpose, it was necessary to rear large numbers of larvae in individual containers. For this reason the rearing equipment described here was designed. The principal advantage gained through its use is that relatively little maintenance is required to achieve fairly constant rearing conditions for large numbers of larvae, with each larva in a separate cage. By combining a number of individual cages into a unit, with its own supply of water and compressed air, attention to the needs of each individual cage is reduced considerably. By adding additional units, the capacity of the equipment can be doubled or trebled, while the corresponding increase in the maintenance requirements is proportionately much lower. In addition to providing an efficient means of rearing larvae in the laboratory, the same equipment can be used in the field under various conditions. Although caddisflies have been the only insects reared up to now, it is altogether likely that similar equipment would be suitable for other aquatic groups as well.