The Other Side of the Coin: Taxonomic Updates and Species Key of Herennia (Araneae: Nephilidae)

Coin spiders of the genus Herennia Thorell, 1877 are species-rich nephilids distributed across South, East, and Southeast Asia and Australasia. They are notable for ladder-shaped arboricolous webs, extreme sexual size dimorphism, and complex sexual behaviors. The most recent revision recognized 11 species, only 4 of which were described from both sexes. Here, we present a taxonomic revision integrating new morphological and molecular data and recognize 14 species. We describe three new species—H. eva Kuntner from Sulawesi, H. maj Kuntner from Vietnam, and H. tsoi Kuntner et al. from Taiwan—and document previously unknown males of H. oz Kuntner, 2005 from Australia and H. tone Kuntner, 2005 from the Philippines. We also extend the known distribution of H. papuana Thorell, 1881 from New Guinea to Australia. Although several molecular species-delimitation analyses suggest H. oz and H. etruscilla Kuntner, 2005 may be conspecific, consistent and diagnostic morphological differences support their recognition as distinct species. We provide an updated identification key to all valid Herennia species. Additional undescribed endemics are likely to occur across the Asian mainland and the rapidly disappearing forests of Southeast Asian and Australasian islands. The genus’ biogeographic pattern, shaped by an ancestrally broad distribution spanning the Wallace Line, may reflect repeated loss and regain of ballooning, a hypothesis that warrants experimental and comparative testing.