Spiders of this genus present perhaps the most obvious case of sexual dimorphism among all of the orb-weaver family, with males being normally 1⁄3 to 1⁄4 the size of females.

Males are differentiated from females by a much smaller and more elongated abdomen, longer legs, and the inability to catch or consume prey bigger than themselves.

Over time, a rather diverse set of spiders was grouped under this genus name, including species from the modern families Araneidae, Mimetidae (Mimetus syllepsicus described by Nicholas Marcellus Hentz in 1832), Tetragnathidae, Theridiidae, Theridiosomatidae (Theridiosoma gemmosum, described by Ludwig Carl Christian Koch in 1877 as Theridion gemmosum), Titanoecidae (Nurscia albomaculata, described by Hippolyte Lucas in 1846 as Epeira albo-maculata) and Uloboridae (Uloborus glomosus, described by Walckenaer in 1842 as Epeira glomosus).

[3] Epeira cylindrica O. P.-Cambridge, 1889 was at a time placed in the Linyphiidae and is considered incertae sedis, as is "Araneus" cylindriformis (Roewer, 1942).

Epeira was synonymized with the genus Aranea by William Elford Leach in 1815, and with Araneus by Eugène Simon in 1904, though this synonymy was not universally recognized.