Abstract The relation between hormones and respiration in adult females of Pyrrhocoris may be expressed by means of three types of respiratory curves. The first is represented by a very high rate which is closely connected with cycles of reproduction and oviposition. Such respiration occurs in ovipositing females when both the activation and corpus allatum hormones are acting. The second type, represented by a steady intermediate rate without cycling, is found in allatectomized or castrated females or in allatectomized castrated females. The third type is a very low rate found in cardiac-allatectomized females whether castrated or not. It is also found in diapausing females and in those from which the brain neurosecretory cells, the corpora cardiaca, and the corpora allata have been removed. The amount of juvenile hormone-dependent respiration (reproduction metabolism), activation hormone-dependent respiration (digestive metabolism), and hormone-independent respiration (muscle and basal cell metabolism) has been estimated. New evidence is given that the juvenile hormone has an indirect effect on respiration due to its increasing the amount of tissue that actively participates in the total metabolism of both larvae and adults. The activation hormone also seems to have an indirect effect on respiration that depends upon its stimulation of metabolism in tissues that are functionally associated with digestion and food utilization. Imaginal diapause in Pyrrhocoris may be induced by a lack of the corpus allatum and activation hormone. The respiratory metabolism of an active female is controlled by the mutual co-operation of both hormones. The activation hormone regulates trophic and the juvenile hormone regulates reproductive functions.