RESUMEN
Butterflies and moths produce enucleate (apyrene) and nucleate (eupyrene) spermatozoa. However, most studies oflepidopteran spermatogenesis and spermiogenesis have used only larvae and pupae. In this work, we used light andtransmission electron microscopy to examine spermiogenesis in males of the butterfly Euptoieta hegesia. Only adultmales were used, because this species has a long adult lifespan during which all cell stages can be observed. Male E.hegesia had a single fused testis with cysts that exclusively contained either apyrene or eupyrene cells. The mainevents of apyrene spermiogenesis included the formation, transformation and elimination of micronuclei, dense capformation, the development of mitochondrial derivatives and tail elongation. Eupyrene spermiogenesis involvedacrosome formation, nuclear condensation and elongation, extracellular appendage development, formation ofmitochondrial derivatives and tail elongation. The pattern and events of apyrene and eupyrene spermiogenesis in E.hegesia corroborate and complement data in the literature, particularly with regard to the intermediate developmentalstages of some structures, such as the acrosome, axoneme and extracellular appendages.