epigyne

An epigyne is a reproductive structure found in certain female spiders, particularly within the family Theridiidae (comb-footed spiders) and some other groups. The term derives from the Greek words *epi-* (meaning "upon" or "above") and *-gynē* (meaning "woman" or "female"), reflecting its anatomical position relative to the spider’s body.

In epigynous spiders, the epigyne is a sclerotized (hardened) plate located on the ventral (underside) surface of the female’s abdomen, just anterior to the spinnerets. This structure serves as a conduit for sperm transfer during mating. When a male spider inserts his pedipalps into the female’s epigyne, sperm is deposited into specialized internal ducts that lead to the fertilizing ducts, where fertilization of the female’s eggs occurs.

The epigyne varies in shape and complexity among different species, often serving as a key identifying feature in taxonomic studies. Some epigynes are simple and smooth, while others exhibit intricate grooves, ridges, or openings that guide sperm to the correct internal chambers. The design of the epigyne can also influence mating success, as it may determine compatibility between male and female spiders of the same species.

Epigynous spiders are common in webs that trap prey, such as black widows (*Latrodectus*) and comb-footed spiders (*Theridion*). The presence of an epigyne distinguishes them from other spider groups, such as prosenic or hysteric spiders, where the genital opening is positioned differently relative to the body. Understanding the epigyne’s function and morphology is essential for both evolutionary studies and practical identification in arachnology.