The genus Xyleborus Eichhoff is the most diverse and complex of the subtribe Xyleborina. There are economically important species within this group, and, given its growing interest, it is necessary to create taxonomic tools to facilitate their identification. Therefore, the present research was focused on the study of the spermathecal capsule. This structure was analyzed in 15 Xyleborus species present in Mexico. Euwallacea posticus (Eichhoff) was included in the study because it was previously part of the genus Xyleborus. Five types of spermathecae were defined within the genus, and all 16 Mexican species have evident differences that allow species separation, including those that are closely related. Distinctive morphological characteristics of the spermathecae are the collum, cornu, nodulus, middle constriction, and general shape.