RESUMEN
Aniara sepulchralis specimens sampled at different locations (Belém and Bragantina microregions) show differences in size of some morphological structures such as head width, pronotum width, distance between eyes, pronotum base width, labral length, labral width, and spur of the third pair of legs. These changes may be due to biotic, abiotic, and structural factors peculiar to each environment. Differences in structures and morphological measurements of males and females of Aniara sepulchralis were observed, characterized as sexual dimorphism in relation to their teeth and labral-clypeal suture. Females present apical teeth and rectilinear suture, whereas males present a more rounded shape in both teeth and the labral-clypeal suture. Regarding measurements, females have greater body length, head width, eye distance, pronotum length, pronotum width, labral length, and pronotum base width than males.