Our understanding of spider reproductive biology is hampered by the vast anatomical diversity and difficulties associated with its study. Although authors agree on the two general types of female spider genitalia, haplogyne (plesiomorphic) and entelegyne (apomorphic), our understanding of variation within each group mostly concerns the external genital part, while the internal connections with the reproductive duct are largely unknown. Conventionally and simplistically, the spermathecae of haplogynes have simple two-way ducts, and those of entelegynes have separate copulatory and fertilization ducts for sperm to be transferred in and out of spermathecae, respectively. Sperm is discharged from the spermathecae directly into the uterus externus (a distal extension of the oviduct), which, commonly thought as homologous in both groups, is the purported location of internal fertilization in spiders. However, the structural evolution from haplo- to entelegyny remains unresolved, and thus the precise fertilization site in entelegynes is ambiguous. We aim to clarify this anatomical problem through a widely comparative morphological study of internal female genital system in entelegynes. Our survey of 147 epigyna (121 examined species in 97 genera, 34 families) surprisingly finds no direct connection between the fertilization ducts and the uterus externus, which, based on the homology with basal-most spider lineages, is a dead-end caecum in entelegynes. Instead, fertilization ducts usually connect with a secondary uterus externus, a novel feature taking over the functional role of the plesiomorphic uterus externus. We hypothesize that the transition from haplo- to entelegyny entailed not only the emergence of the two separate duct systems (copulatory, fertilization), but also involved substantial morphological changes in the distal part of the oviduct. Thus, the common oviduct may have shifted its distal connection from the uterus externus to the secondary uterus externus, perhaps facilitating discharge of larger eggs. Our findings suggest that the conventional model of entelegyne reproduction needs redefinition.

The desmitracheate system in a “micronetine” genus Nippononeta Eskov, 1992 is recognized for the first time in the present study. This makes the subfamilial placement of this genus problematic. A morphological study was conducted for N. kurilensis Eskov, 1992 (the type species of Nippononeta) and N. coreana (Paik, 1991). Characters of genitalia and tracheal system, as well as some somatic characters were studied in detail by using scanning electronic microscopy (SEM), and compared with those of Agyneta. Updated descriptions of the genus Nippononeta and its two species are presented. Putative synapomorphies for Nippononeta and Agyneta are provided, as well as some putative synapomorphies shared by the two genera. The results imply that both scaped epigynum and desmitracheate tracheal system are probably homoplastic. The placement of Nippononeta and Agyneta within Linyphiidae need to be resolved in future studies.

A new “micronetine” genus Acanoides gen. n. is erected to accommodate two species from China: Acanoides beijingensis sp. n. as the type species and Acanoides hengshanensis (Chen & Yin, 2000), comb. n., with the females described for the first time. The genitalic characters and somatic features of the new genus were studied by means of light microscopy and scanning electron microscopy (SEM). The monophyly of the new genus was tested by a phylogenetic analysis based on molecular data. Descriptions of the new genus, the new species and the new combination are presented; SEM images and microscopy pictures of somatic and genitalic characters are provided in detail. To distinguish from other genera with similar genitalic characters, we compare the new genus with the species of Acanthoneta Eskov & Marusik, 1992, Epibellowia Tanasevitch, 1996 and Wubanoides Eskov, 1986. Four putative synapomorphies for Acanoides gen. n. are suggested to support its monophyly that could be tested in the future. Furthermore, redescriptions of the epigynal morphology of Acanthoneta aggressa Chamberlin & Ivie, 1943 (Nearctic) and on the male of A. dokutchaevi Eskov & Marusik, 1993 (Far East Asia, firstly recorded from China) are provided. Based on comparison with Poeciloneta, from which Acanthoneta stat. n. was separated by Saaristo and Tanasevitch (1996), a revised diagnosis is proposed to support the generic status.

A time scale of phylogenetic relationships contributes to a better understanding of the evolutionary history of organisms. Herein, we investigate the temporal divergence pattern that gave rise to the poor species diversity of the spider genus Solenysa in contrast with the other six major clades within linyphiids. We reconstructed a dated phylogeny of linyphiids based on multi-locus sequence data. We found that Solenysa diverged from other linyphiids early in the Cretaceous (79.29 mya), while its further diversification has been delayed until the middle Oligocene (28.62 mya). Its diversification trend is different from all of the other major lineages of linyphiids but is closely related with the Cenozoic ecosystem transition caused by global climate changes. Our results suggest that Solenysa is a Cretaceous relict group, which survived the mass extinction around the K-T boundary. Its low species diversity, extremely asymmetric with its sister group, is largely an evolutionary legacy of such a relict history, a long-time lag in its early evolutionary history that delayed its diversification. The limited distribution of Solenysa species might be related to their extreme dependence on highly humid environments.

The present paper gives a review of Solenysa species from Japan and provides a solution for the species bearing the generotype name S. mellotteei Simon, 1894. A total of six species are recorded, including two new species S. macrodonta sp. n. and S. trunciformis sp. n. The species collected from Kawasaki (NSMT-Ar 11154) and Hachioji should be the generotype S. mellotteei, with S. akihisai Tu, 2011, syn. n. as its junior synonym. To distinguish these congeneric species from each other, their genital characters are provided in detail based on images collected by scanning electron microscopy and light microscopy.