Epigyne

The external anatomy of a spider, with the epigyne labeled
The internal anatomy of a spider, with the reproductive system (purple) reaching the exoskeleton at the epigyne

The epigyne or epigynum is the external genital structure of female spiders. As the epigyne varies greatly in form in different species, even in closely related ones, it often provides the most distinctive characteristic for recognizing species. It consists of a small, hardened portion of the exoskeleton located on the underside of the abdomen, in front of the epigastric furrow and between the epigastric plates.[1]

  1. ^ Comstock, John Henry (1920) [First published 1912]. The Spider Book. Doubleday, Page & Company. pp. 129–132.