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. In A. diadematus, for example, last molt females can reach the body size of up to 1 in (2.5 cm), while most males seldom grow over 0.3 in (1 cm), both excluding legspan. 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.
Araneus was originally called Epeira. The latter name is now considered a junior synonym of Araneus.
It was first coined by Charles Athanase Walckenaer in 1805, for a range of spiders now considered Araneidae (orb-weavers). Over time, a rather diverse set of spiders was grouped under the genus Epeira, including species from the modern families Araneidae, Mimetidae (Mimetus syllepsicus described by Hentz, 1832), Tetragnathidae, Theridiidae, Theridiosomatidae (Theridiosoma gemmosum, described by L. Koch, 1877 as Theridion gemmosum), Titanoecidae (Nurscia albomaculata, described by Lucas, 1846 as Epeira albo-maculata) and Uloboridae (Uloborus glomosus, described by Walckenaer, 1842 as Epeira glomosus). Epeira cylindrica O. P-Cambridge, 1889 was at a time placed in Linyphiidae and is considered incertae sedis, as is "Araneus" cylindriformis (Roewer, 1942).
Throughout the 19th century, Epeira was used as a catch-all genus, similar to the once ubiquitous salticid genus Attus. However, from 1911, to its last mention in 1957, only very few authors continued to use the genus in their publications, notably Franganillo (1913, 1918), Hingston (1932), Kaston (1948) and Marples (1957). Chamberlin and Ivie published a new species, Epeira miniata, in 1944, which was rejected.
Jean-Henri Fabre refers to Argiope spiders as Epeira in his 1928 book The Life of the Spider (La Vie des araignées), within the family "Epeirae". James Henry Emerton also uses the genus Epeira in his 1902 book The Common Spiders of the United States, but refers to spiders mostly now considered Araneus. The popular 1893 book American Spiders and their Spinningwork by Henry Christopher McCook also uses Epeira extensively.