The microtubular arrays characteristic of the trophic core and cords of the adult Rhodnius prolixus ovary develop prior and during the larval--adult transformation. Development of the microtubules was revealed by immunocytochemistry, electron microscopy and polyacrylamide electrophoresis and Western blot analysis. Microtubular arrays were first detected in the trophic cords and presumptive trophic core 6 days before the adult molt. Cord microtubules increase in length and numbers as the trophic cords grow. Three microtubule packed cords have formed by 1 day post molt. The microtubule distribution in the presumptive core is non-uniform. Microtubule packed areas are interspersed with areas devoid of microtubules. The adult core begins forming between 1 day before molt and molting. This early adult core arises from the fusion of the anterior portions of microtubule packed cords. A fully mature adult core is not present by 2 days post molt. The microtubule packing density in the core increases from 2 days before to 2 days post molt. Tubulin increases from 6 days to 1 day before the adult molt.