A procedure for rearing Manduca sexta (Johannson) in a simple and effective manner is described, and its use in a mass rearing program is considered. The procedure is an open, nonsterile system in which larvae are reared collectively in trays and synchrony of development is manipulated by means of photoperiods. The ingredients of an artificial diet, a diagram of the rearing tray, the yield at various stages of growth, and aspects of the behavior of the larvae also are provided.