Proallatotoxins, and particularly precocenes, are exceptionally promising models for studying Rhodnius prolixus physiology and for comparison with other natural compounds with antihormonal activities. Effects of precocenes on feeding, development and reproduction of R. prolixus are being detailed. The precocenes reveal significant effects on feeding, moulting cycle (inducing precocious metamorphosis and ecdysial stasis), and reproduction of these insects. The mechanism of action of proallatotoxins was discussed based on the corpus allatum cytotoxic effect and on the ecdysteroid biosynthesis in prothoracic glands and ovaries. Further studies of these compounds on R. prolixus are need and will hopefully reveal other unexplored points regarding the action of the proallatotoxins on insects.