The classification of the ovarian stages remains still vague. The ultrastructure of the basal follicle made it possible to solve this problem. From the sixth to the eighth day of the worker bee's adult life, the length of the ovariole hardly exceeds 2 mm. The basal oocytes of stages 1 and 2 are characterized by the presence of many ranges of granules encircled by the dilated cylinders of the granular endoplasmic reticulum. These cylinders decondensate the proteinic granules and the lipidic globules generating multivesicular bodies. The basal oocyte, at the third stage of development, measures 0.35+/-0.05 mm in length. This stage of the previtellogenesis' end is characterized by the appearance, in the ooplasm, of many tubules, whose dilated end constitutes a lysosome. At the beginning of the second week, vitellogenesis starts. Stage 4 is defined by the appearance, in the ooplasm, of the yellow granules in relationship to the tubular formations. At the 14th to 16th days of the adult life, 25+/-7.1% of the worker bees reach the end vitellogenesis, or stage 5. The ovariole, about 7 mm in length, contains 11 follicles. This stage 5 is distinguished by the synthesis from the vitelline membrane, the regression of the size of yellow granules and the accessory cores. The sixth stage or oocyte maturation is reached by 12.5+/-3.5% of the workers aged 18 to 20 days. It is defined by the presence of the chorion, the dissolution of the yellow granules, the disappearance of the accessory nuclei and the total degeneration of the follicular cells.