Nesticus mogera Yaginuma, 1972 from Japan.

Japan, Tokyo Pref., Tamagawa.

Japan: Honshu Is.: Miyagi Pref.: 1♀, Tome-gun, Lake Izunuma, 20.July.1986, A. Tanikawa leg. (MNHAH); 6♂, 4♀, Tamatukuri-gun, Naruko-cho, Myousada, 7–10.May.1996, K. Kumada leg. (NMST-Ar.3587); Akita Pref.: 1♀, Akita-shi, Shimokitateyanagitate, Kagawa, 21.Nov.2005, A. Fukushima leg. (NSMT-Ar.20405, identified as N. brevipes); Yamagata Pref.: 1♀, Tsuruoka-shi, Oyama, 38.75628°N, 139.76331°E, 26.Aug.2019, Y. Suzuki leg. (YSPC); Tochigi Pref.: 1♂ Tochigi-shi, Fujoka-machi, Uchino, Watarase-Yusuichi, 36.2353°N, 139.6574°E, Alt.: 20 m, 2.Apr.2022, N. Kikuchi leg. (FBPC); Tokyo Pref.: 1♂ (holotype), Tamagawa, 3.Feb.1969, H. Kobayashi leg. (NMST-Ar.73); 1♂, 2♀, Hachioji-shi, Minami-Osawa, Tokyo Metropolitan University campus, litter under bushes, 35.6245°N, 139.3863°E, 22.Sep.2020, F. Ballarin leg. (FBPC); Hachijo-jima Is.: 3♂, 3♀, Okago, Hachijo Botanical Park, forest litter, 33.11044°N, 139.78432°E, 03.May.2021, F. Ballarin leg. (FBPC); Kanagawa Pref.: 1♂, 2♀, Kawasaki-shi, Nakahara-ku, Kasugi-cho, Dec.1984 (exact date unknown), H. Ono leg. (NMST-Ar.893); 2♀, Yokohama-shi, Maioka park, 6.July.1986, A. Tanikawa leg. (MNHAH); Nagano Pref.: 2♀, Ueda-shi, 8.Sep.1998, Y. Fujisawa leg. (NMST-Ar.6965); 3♀, Kamiina-gun, Ijima-cho, 35.67049°N, 137.91159°E, 09.Sep.2019, Y. Suzuki leg. (YSPC); Shizuoka Pref.: 1♀ (Paratype), Tenryu-shi, Mar.1970 (exact date unknown), H. Kobayashi leg. (NMST-Ar.74); 1♀, Hamamatsu-shi, Kita Ward, Inasacho Okuyama, 34.85102°N, 137.62569°E, under grass tuffs in a paddy field, 30.Sep.2019, F. Ballarin leg. (FBPC); Fukui Pref: 1♀, Tsuruga-shi, Nagatani, under grass tuffs in a paddy field, 35.60836°N, 136.03872°E, 3.Oct.2019, F. Ballarin leg. (FBPC); Mie Pref: 1♀, Iga-shi, Otani, under grass tuffs in a paddy field, 34.79919°N, 136.13501°E, 7.Oct.2019, F. Ballarin leg. (FBPC); Kumamoto Pref.: 2♂, 1♀, Tamana-gun, Gyokutou-machi, Harakura, Yamakitasho-no-ana cave (山北小の穴), 20.May.1984, T. Irie leg. (NMST-Ar.16065); Kagoshima Pref.: 1♀, Minami Kyushu-shi, Kawabe-cho, 26.Feb.2007, K. Iohii(?) leg. (NMST-Ar.14585); Yakushima Is.: 1♂, Anbo, 207 m, broadleaf forest litter on a gentle slope 30.28458°N, 130.61799°E, 24.Sep.2021, F. Ballarin leg. (FBPC); Suwanosejima Is.: 1♂, 2♀, Otohime-no-dokutsu cave, 8.Jul.2022, Y. Suzuki leg. (YSPC); Amami-Ōshima Is.: 1♂, Amami-shi, Kasarichō Ōaza Kise, 2 m, at the base of tufts of grass on a sandy seashore, 28.46221°N, 129.65013°E, 13.Jul.2021, F. Ballarin leg. (FBPC); Okinawa Pref.: Okinawa-Honto Is.: 1♀, Naha-shi, Sueyoshi park, 70 m, humid broadleaves litter under trees, 26.22840°N, 127.71508°E, 21.Nov.2020, F. Ballarin leg. (FBPC); 1♂, 4♀, Nakagami-gun, Yomitan-son, Namihira, Shimuku Gama cave (シムクガマ), Alt.:72 m, large and long cave with a creek, 26.40242°N, 127.73125°E, 15.May.2022, F. Ballarin leg. (FBPC); Aka-jima Is.: 3♀, 17.Mar.2022, Y. Suzuki leg. (YSPC); Kume-jima Is.: 1♂, Shimajiri-gun, Gima, Nameless Beach, under vegetation on a sandy seashore, 26.32681°N, 126.77002°E, Alt.: 3 m, 17.May.2022, F. Ballarin leg. (FBPC); Miyako-jima Is.: 1♀, Nobaru Ueno, Pinza-Abu cave (ピンザアブ洞穴), 57 m, long and muddy cave, dark zone, 24.74853°N, 125.33443°E, 13.Nov.2020, F. Ballarin leg. (FBPC); Ishigaki-jima Is.: 4♀, Tonoshiro, Fukubukuīzā Daiichi-do cave (フクブクイーザー第1洞), 66 m, long and humid cave with a small creek, 24.36533°N, 124.17721°E, 9.Nov.2020, F. Ballarin leg. (FBPC); 4♀, same locality, 11.Nov.2020, F. Ballarin leg. (FBPC) ; Yonaguni-jima Is.: 1♀, Irizaki, under stones in a meadow near the seashore, 24.44499°N, 122.9411°E, 30 m a.s.l., 4.Mar.2021, F. Ballarin leg. (FBPC).

This species is closely related to H. alba sp. nov. and H. subterranea sp. nov. from which it can be easily distinguished by the presence of pigmentation and well-developed eyes (vs pigmentation and eyes lacking in both the other species) (Fig. 1H–J cf. Figs 2H–J, 3A–C). Males of H. mogera can also be separated from males of H. alba sp. nov. by the thinner paracymbium (P) and the more squared and stockier distal process of paracymbium (Di) (vs wider P and longer and slightly sharper Di in H. alba sp. nov.) (Figs 1A, B, D, 4A–C cf. Figs 2A, B, D, 4E–G). Females of H. mogera are distinguished from females of H. alba sp. nov. and H. subterranea sp. nov. by the shape of scapus (Sc), rectangular and with a flat posterior margin (vs stockier and larger Sc in H. alba sp. nov. or longer and distally dilatated Sc in H. subterranea sp. nov., both having a rounded posterior margin) (Figs 1E–G, 4D cf. Figs 2E–G, 3D, E, 4H, 13E). See also Lin et al. (2016) for the diagnosis of H. mogera with other congeners of the same species group.

Figure 1. 

Howaia mogera A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne ventral view (specimen from Tokyo area) F same after dissection, shape variation G vulva, dorsal view H habitus of male (specimen from Tokyo area) I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 1.0 mm (H, I).

Figure 2. 

Howaia alba sp. nov. A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (one of the paratypes), ventral view F same, shape variation G vulva, dorsal view H habitus of male (holotype) I habitus of female (one of the paratypes) J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 1.0 mm (H, I).

Figure 3. 

Howaia subterranea sp. nov. A habitus of female (holotype) B cephalic area of female, frontal view C habitus of female, lateral view D female epigyne, ventral view E vulva, dorsal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 1.0 mm (A, C); 0.2 mm (B, D, E).

Figure 4. 

Genitalia of Howaia mogera and H. alba sp. nov. A male palp of H. mogera, ventral view B same, retrolateral view C detail or paracymbium, dorsal view E female epigyne, ventral view E male palp of H. alba sp. nov., ventral view F same, retrolateral view C detail or paracymbium, dorsal view H female epigyne, ventral view. Abbreviations: Cl – lobe of conductor; Cm – median process of conductor; Co – copulatory opening; Cp – prolateral process of conductor; Cr – retrolateral process of conductor; Di – distal process of paracymbium; E – embolus; P – paracymbium; Ra – radical apophysis; Rx – radix; S – spermatheca; Sc – scapus; Sd – sperm duct; St – subtegulum; Te – tegulum; Ve – ventral process of paracymbium. Scale bars: 0.2 mm.

(holotype). (redescription of habitus based on freshly collected specimen from Tokyo area due to the discoloration of the holotype). Habitus as in Fig. 1H. Total length. 1.94, Prosoma 1.10 long, 0.89 wide. Carapace rounded, yellowish with slightly darker striae. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.06, ALE = 0.09, PME = 0.09, PLE = 0.09, AME–ALE = 0.03, ALE–PLE = 0.00. Chelicerae, labium, maxillae, and sternum of same color as carapace. Legs uniformly yellowish. Legs measurements: I 5.07 (1.41, 0.43, 1.30, 1.24, 0.69), II 3.85 (1.10, 0.38, 0.90, 0.89, 0.58), III 3.26 (0.97, 0.33, 0.73, 0.73, 0.50), IV 4.44 (1.29, 0.40, 1.11, 1.06, 0.58). Opisthosoma uniformly dark grey with slightly lighter mark on antero-dorsal side.

Male palp as in Figs 1A–D, 4A–C. Cymbium relatively elongated, 3–4 robust spines on distal-prolateral margin (Fig. 1D). Paracymbium with 1 distal (Di) and 1 ventral (Ve) processes. Distal process short, squared, and stocky, distinctly sclerotized. Ventral process sharp, spine-like, headed internally (Figs 1A–D, 4A–D). Embolus (E) long and filiform, origin of embolus positioned at ~ 6:00 o’clock on radix (Rx). Radical apophysis (Ra) broad and dorsally flat with a granulate surface. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process (Cp) flat and long, ribbon-like, headed counterclockwise, wrapped around the embolus. Retrolateral process of conductor (Cr) wide and thick, curved internally, with a broadened, flat central part. Median process of conductor (Cm) strongly sclerotized, short and stout, horn-like, ending with a blunt tip and having a smaller, stout ventral process (Figs 1A–C, 4A, B).

(based on specimen from Tokyo). Habitus as in Figs 1I, 15A. Total length: 2.44, Prosoma 1.19 long, 0.98 width. Cephalic area as in Fig. 1J. Carapace piriform. Eyes measurements: AME = 0.05, ALE = 0.08, PME = 0.08, PLE = 0.08, AME–ALE = 0.04, ALE–PLE = 0.01. Legs measurements: I 4.93 (1.42, 0.44, 1.28, 1.15, 0.64), II 3.96 (1.08, 0.39, 0.85, 0.78, 0.54), III 2.88 (0.86, 0.33, 0.63, 0.62, 0.44), IV 4.22 (1.30, 0.41, 1.10, 0.89, 0.52). Coloration and other details as in male.

Epigyne and vulva as in Figs 1E–G, 4D. Scapus (Sc) elongated antero-posteriorly, rectangular, slightly longer than wide, ending with a flat posterior margin (Figs 1E–G, 4D). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, V-shaped. Copulatory ducts (Cd) straight, short, and thick, gradually diverging from each other, slightly coiled in the first half of the trait before reaching the spermathecae. Insemination ducts (Id) thin, coiled around the copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 1.5 their diameter (Fig. 1G).

Male (based on 5 specimens): total length: 1.89–2.02, prosoma length: 0.84–1.07, prosoma width: 0.76–0.85. Female (based on 10 specimens): total length: 2.08–2.88, prosoma length: 0.96–1.15; prosoma width: female: 0.87–0.96.

East Asia (from South China to Korea and Japan). Introduced to Europe, Azerbaijan, and several oceanic islands (Hawaii, Fiji, Reunion, St. Helena, etc.). Although it is likely that H. mogera is naturally distributed in Asia, its precise center of origin, as well as the time and mode of its dispersion outside the Asian continent, are still unstudied. In Japan the species is widespread along the whole country in both mainland Japan and the Ryukyus (Fig. 16C, D).

This species has a broad environmental tolerance. In Japan H. mogera can be found in a wide range of habitats, both natural and artificial, including caves, mines, artificial tunnels, small animal burrows, forest leaf litter, humid meadows, paddy fields, marshes, urban parks, greenhouses, vegetated seashores, coastal environments, etc. Howaia mogera usually builds simple scaffold webs in external habitats, under superficial stones, in empty spaces among the leaf litter or at the base of tufts of grass. Apparently, the populations living in mainland Japan are found less commonly in caves or cave-like habitats. In contrast, in addition to epigean environments, the populations living in the Ryukyu islands can be found more frequently in natural subterranean habitats, dwelling in both the twilight and dark areas of caves and tunnels.

Coloration and pattern of the opisthosoma can be rather variable, depending on the population or individual. Usually, populations living in mainland Japan show a darker habitus with an opisthosoma uniformly black or dark grey, sometimes having one or few small lighter marks on the dorsal side (Figs 1H, I, 15A). Instead, individuals living in the Ryukyus seems to show a lighter pattern bearing several larger greyish dorsal marks, often merged together forming a continuous median stripe. Such pattern is shared by the southern Chinese populations (see Liu and Li 2013: fig. 18B). Legs are usually uniformly yellowish; however, some individuals show a faint darker annulation on the distal part of femur and tibia. The shape of scapus can also be slightly variable among individuals or populations, ranging from strongly rectangular to slightly inverted-trapezoidal or shorter and more squared, more rarely with strongly rounded distal margin (e.g., see Fig. 1E, F and Liu and Li 2013: fig. 18C, D). Yaginuma (1972: 620) illustrated a scapus with a strongly triangular shape for the paratype of H. mogera. Such extreme shape is abnormal and never observed by us in any of the examined specimens. In addition, the drawing by Yaginuma does not perfectly match with the shape of the scapus of the original sample (paratype NMST-Ar.74 from Tenryu-shi) which shows a normal rectangularly-shaped scapus.

Howaia mogera was initially misidentified by Yaginuma (1970) and described as the male of Nesticus (= Nesticella) terrestris based on a specimen from Tamagawa, Tokyo. Soon after Yaginuma recognized the mistake and described the species as new based on the same male together with a female specimen from Shizuoka (Yaginuma 1972). Until now H. mogera has been recorded in several different countries and redescribed and illustrated numerous times by different authors (World Spider Catalog 2023). However, these descriptions were all based on specimens collected far from the type locality, in different Asian countries (e.g., Korea: Kim et al. 1999, Kim and Lee 2018; China: Gong and Zhu 1982, Liu and Li 2013) or based on introduced populations (e.g., Fiji Is.: Lehtinen and Saaristo 1980; Hawaii Is.: Gertsch 1984; Azeirbaijan: Marusik and Guiseinov 2003; Poland: Bielak-Bielecki and Rozwalka 2011; Italy: Pantini et al. 2020). Herein, for the first time after the original description, we illustrate and redescribe the holotype and additional specimens from the type locality area.

In the past, the lack of information about the taxonomy of H. mogera, and in general on Nesticella species, has been the cause of misidentifications by senior arachnologists, sometimes confusing this species with other similar congeners. For example, the male of the blind H. mogera specimens from Miyako-jima Is. illustrated by Shimojana (1977) refers to the newly described H. alba sp. nov. Paik (1996) recorded Nesticus (= Nesticella) brevipes from South Korea based on female specimens. The illustrated samples do not match the morphology of this species (cf. Figs 5I, E–G, 7D and Paik 1996: figs 1–10) and probably they refer to more than one species of Nesticella or Howaia. Among them, the shape of epigyne and internal ducts of the specimens of the so-called groups A or B fits well with those of H. mogera (Paik 1996: figs 6, 9, 10). Illustration of the female of H. mogera by Zhu and Zhang (2011: fig. 34A–C), clearly do not refer to this species, the illustrated epigyne and vulva being morphologically different from those found in the genus Howaia.

Previous molecular analyses suggest that populations of H. mogera in Eastern Asia group into two well-distinct subclades with non-overlapping distribution, distributed respectively in North-Eastern Asia (= north clade) and South China (= south clade) (Zhang and Li 2013; Ballarin and Li 2018; this work). In Japan both these two clades are apparently present. The north clade is distributed in mainland Japan covering the islands of Hokkaido, Honshu, Shikoku, and Kyushu. Its southernmost boundary seems to correspond to the island of Yakushima (Fig. 16C). The south clade shares the same genetic pattern of the southern China populations (Fig. 14) and it is widespread along the whole Ryukyus and in the island of Hachijo-jima Is., south of Tokyo (Fig. 16C, D). The presence of the south clade in Hachijo-jima Is., far away from the other known records, suggests a possible artificial introduction to this island. Some degrees of genetic difference (2.5–3.7%) and slight variations in the body pattern and habitat preference can be observed in populations belonging to the two clades (see remarks on habitat and variation discussed above). Nevertheless, no clear distinct morphological differences are observed in their genitalia. The result of our species delimitation analysis only partially supports them as two distinct species (Fig. 14). It is possible that they represent two cryptic species or, more likely, an early stage of species differentiation which is still in progress nowadays.

♂ Holotype (NMST-Ar. 25251): Japan: Okinawa Pref.: Miyako-jima Is.: Shimozato Hirara, Oharaminami Park, Tsuzupisuki-abu cave (ツヅピスキアブ), 32 m, long and humid cave, in the dark zone of the cave, 24.79468°N, 125.28192°E, 12.Nov.2020, F. Ballarin leg.

Paratypes: Japan: Miyako-jima Is.: 3♀, same data as the holotype (NSMT-Ar 25252); 1♀, same locality 14.Nov.2020, F. Ballarin leg. (RMUF); 5♀, same locality, 16.Sep.2022, F. Ballarin leg. (2♀ MNHAH, 3♀ FBPC); 4♀, Nobaru Ueno, Pinza-abu cave (ピンザアブ洞穴), 57 m, long and muddy cave, in the dark zone of the cave, 24.74853°N, 125.33443°E, 13.Nov.2020, F. Ballarin leg. (RMUF); 3♀, same locality, 17.Sep.2022, F. Ballarin leg. (FBPC).

Japan: Miyako-jima Is.: 1 juv., Nakabari, Nakabari Limestone Cave (仲原鍾乳洞), 24.73384°N, 125.37610°E, 29.Dec.2021, R. Miyata leg. (FBPC).

The specific name is derived from the Latin word for the color white (albus, adjective) referring to the whitish coloration of the species.

The new species is similar to H. mogera and to the troglobitic species H. rongtangensis (Lin, Ballarin & Li, 2016) from Hainan Island, H. subterranea sp. nov., and N. occulta sp. nov. Male of H. alba sp. nov. can be distinguished from male of H. mogera and H. rongtangensis by the different shape of the larger paracymbium (P) bearing a longer, slimmer, and sharper distal process (Di) (vs slimmer P with a shorter, larger, and blunter Di in H. mogera and H. rongtangensis) (Figs 2A–D, 4E–G cf. Figs 1A–D, 4A–C and Lin et al. 2016: fig. 44A, B, D). Female of the new species are distinguished from female of H. mogera, H. subterranea sp. nov., and N. occulta sp. nov. by the larger and stockier scapus (Sc) with a slightly rounded posterior margin (vs slimmer Sc with a flat posterior margin in H. mogera, a longer Sc with a wider lobated tip in H. subterranea sp. nov., and a slimmer, tongue-like Sc ending with a strongly concave tip in N. occulta sp. nov.) (Figs 2E–G, 4H cf. Figs 1E–G, 3D, E, 4D, 11C, D, 13E, F).

(holotype). Habitus as in Fig. 2H. Total length 1.88. Prosoma 0.94 long, 0.83 wide. Carapace uniformly pale yellowish. Eyes completely degenerated and reduced to white maculae. Cervical groove and fovea indistinct. Chelicerae brownish. Labium, maxillae, and sternum of the same pale color as carapace. Legs uniformly pale yellowish. Leg formula: I, IV, II, III. Legs measurements as follows: I 6.17 (1.61, 0.47, 1.60, 1.72, 0.77), II 4.71 (1.32, 0.39, 1.20, 1.18, 0.62), III 3.89 (1.11, 0.31, 0.95, 1.02, 0.50), IV 5.17 (1.50, 0.37, 1.34, 1.31, 0.65). Opisthosoma uniformly greyish-yellow, covered with long, sparse hairs.

Male palp as in Figs 2A–D, 4E–G. Cymbium relatively elongated, covered with thin sparse setae, bearing some thicker setae on the distal-prolateral margin (Fig. 2D). Paracymbium with a single distinctly sclerotized, stocky distal process (Di), slightly elongated near the tip and a single sharp, spine-like ventral process (Ve) (Figs 2A–D, 4E–G). Embolus (E) long and filiform, origin of embolus positioned at ~ 6:00 o’clock on radix (Rx). Radical apophysis (Ra) broad, with a granulate surface. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of the conductor (Cp) flat, ribbon-like and headed counterclockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved internally, with a broadened, flat central part. Median process of conductor (Cm) stout, horn-like, strongly sclerotized bearing a smaller, stout ventral process. (Figs 2A–C, 4E, F).

(one of the paratypes). Habitus as in Figs 2I, 15C. Total length 2.3. Prosoma 1.09 long, 0.92 wide. Cephalic area as in Fig. 2J. Coloration and other details as in male. Legs measurements as follows: I 6.56 (1.83, 0.50, 1.74, 1.67, 0.82), II 5.09 (1.46, 0.42, 1.27, 1.22, 0.72), III 4.09 (1.31, 0.36, 0.90, 0.92, 0.60), IV 5.46 (1.65, 0.45, 1.42, 1.27, 0.67).

Epigyne and vulva as in Figs 2E–G, 4H. Scapus (Sc) short and stumpy, approximately as long as wide, ending with a slightly rounded posterior margin (Figs 2E, F, 4H). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as a narrow V. Copulatory ducts (Cd) short and thick, slightly divergent to each other, slightly twisted in the inner trait with 1 coil, curving outward and then inward before reaching the spermathecae. Insemination ducts (Id) thin, coiled around the Cd). Spermathecae (S) small and rounded, separated from each other by ~ 2× their diameter (Fig. 2G).

Female (based on 5 specimens): total length: 2.00–2.67, prosoma length: 1.05–1.12, prosoma width: 0.92–0.97.

Endemic to Miyako-jima Is., Ryukyus, Japan (Fig. 16B).

Howaia alba sp. nov. is found in the natural caves in Miyako-jima Is. This species builds simple scaffold webs between rocks and in crevices at the base of the walls or on the floor of the caves. It dwells exclusively in the dark zone of the caves, in areas characterized by relatively high and uniform temperature and humidity (e.g., Tsuzupisuki-abi cave: temp: 25.2 °C, hum: 94.1%; Pinza-Abu cave: temp: 25.1 °C, hum: 92.6%) (Fig. 15G). Adults of Howaia alba sp. nov. were observed preying on Schizomida (Bamazomus siamensis (Hansen, 1905) which roam the floor of the caves in Miyako-jima Is. Females carrying the eggs cocoon attached to their spinnerets were also observed (but not collected) sitting on webs or wandering under rocks. Despite extensive surveying, no specimens were found in the numerous artificial tunnels or underground water reserves dug in the limestone rocks of the island. The complete absence of eyes and pigmentation, the lack of external records and the finding of the species only in the deepest areas of the caves identify H. alba sp. nov. as a true troglobiont.

This species was recorded and illustrated for the first time by Shimojana (1977: fig. 6A–C). Due to the general similarities in the shape of genitalia, it was identified as H. mogera although the author highlighted the lack of eyes in these specimens (Shimojana 1977: 353). Our analysis, based on both morphology and molecular data, supports H. alba sp. nov. as a closely related species but clearly distinct from H. mogera.

♀ Holotype: Japan: Kagoshima Pref.: Okinoerabu-jima Is.: 1♀, Kaikendo cave (海見洞), 3.May.2004 H. Tamura leg. (NSMT-Ar 25253).

The new species is named after the Latin adjective subterraneus (= underground, subterranean). It refers to the troglobitic lifestyle of this species.

This species is similar to H. mogera and the other troglobiont species H. alba sp. nov. and N. occulta sp. nov. Howaia subterranea sp. nov. can be distinguished from these species by the different shape of the epigyne, having curved internal ducts (vs straight ducts in the other three species), and a longer scapus (Sc) with an enlarged tip (vs a shorter and more rectangular Sc with a flat distal margin in H. mogera, a shorter and stockier Sc in H. alba sp. nov., and a shorter, tongue-like Sc in N. occulta sp. nov., all of them lacking a clearly enlarged tip) (Figs 3D, E, 13E cf. Figs 1E–G, 2E–G, 4D, H). In addition, the new species can be easily distinguished from H. mogera and the other Japanese species by the lack of eyes and pigmentation (vs present in the other troglophilic congeners).

Female (holotype). Habitus as in Fig. 3A, C. Total length 2.65. Prosoma 1.20 long, 0.93 wide. Carapace piriform, uniformly pale yellowish. Eyes strongly degenerated, reduced to white maculae (Fig. 3B). Cervical groove and fovea indistinct. Chelicerae uniformly brownish. Labium, maxillae, and sternum pale yellowish as carapace. Legs uniformly pale yellowish. Legs measurements (leg III missing): I 6.73 (1.95, 0.46, 1.82, 1.65, 0.85), II 5.24 (1.56, 0.45, 1.29, 1.22, 0.72), III (-), IV 5.75 (1.76, 0.46, 1.54, 1.32, 0.67). Opisthosoma uniformly greyish, covered by long, sparse hairs.

Epigyne and vulva as in Figs 3D, E, 13E. Scapus (Sc) elongated antero-posteriorly, ~ 2× longer than wide, ending with an enlarged, lobated tip (Figs 3D, 13E). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as a narrow curly bracket. Copulatory ducts (Cd) bent in middle trait, first trait slightly curved outward then curving anteriorly before reaching spermathecae (Figs 3D, E, 13E). Insemination ducts (Id) thin, coiled around the copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 2.5× their diameter (Fig. 3D, E).

Male. Unknown.

Endemic to Okinoerabu-jima Island. Known only from the type locality (Fig. 16B).

Howaia subterranea sp. nov. has probably been collected in the dark zone of the type locality cave. The lack of pigmentation and the strongly reduced eyes further suggest this species as a true troglobiont. Nevertheless, the lack of specimens and additional information do not allow us to define in detail the ecology and micro-habitat preference of this species as well as its precise phylogenetic position. Nevertheless, the morphology of epigyne clearly identify H. subterranea sp. nov. as belonging to the genus Howaia.

Nesticus nepalensis Hubert, 1973 from Nepal.

Japan Shikoku Is., Kochi Pref., Tosa-Yamada-cho, Sakagawa, Ryuga-dō cave (龍河洞).

Japan: Honshu Is.: Wakayama Pref.: 1♀, Higashimuro-gun, Kushimoto, 23.Aug.1993, A. Tanikawa leg. (FBPC); Shiga Pref.: 1♀, Koga, Shigaraki-cho, Miyajiri, 28.Jun.2022, M. Yoshida leg. (FBPC); 1♀, Otsu, Sakamoto, 23.Jul.2022, M. Yoshida leg. (FBPC); Shikoku Is.: Tokushima Pref: 2♀, Tokushima, Nyūtachō, Konji, Konjiji temple (建治寺), narrow and dry tunnel in the cliff near the temple, 34.02769°N, 134.42923°E, 13.May.2019, F. Ballarin leg. (FBPC); Kochi Pref.: 1♀ (holotype), Kami, Tosayamadacho Sakakawa, Ryuga-dō cave (龍河洞), 11.Apr.1970, S. Ueno leg. (NMST-Ar.75); 1♂ (paratype), same data and locality (NMST-Ar.76); Kyushu Is.: Saga Pref.: 1♀, Fujicho, 31.Jul.2005, A. Tanikawa leg. (MNHAH); Kumamoto Pref.: 1♂, 3♀, Aso-gun, Aso-machi, Kikuchi Keikoku gorge, 8.Aug.2003, T. Irie leg. (NSMT-Ar.5689); same locality, 11.Jul.2004, T. Irie leg. (NSMT-Ar.5713); 1♂, 2♀, Kami-mashiki-gun, Tonochi-machi, Kashiwagawa, 23.May.2004, T. Irie leg. (NMST-Ar.5728, identified as H. mogera); 1♀, Kuma-gun, Itsuki-mura, Otaki, 13.May.2004, T. Irie leg. (NMST-Ar.5721); Ōita Pref.: 2♀, Ōita-shi, Ochi Shimohetsugi, Ōzuru-doukustu-iseki cave (尾津留洞窟遺跡), 38 m large and rather dry cave, 33.16747°N, 131.67679°E, 17.Mar.2019, F. Ballarin leg. (FBPC); Kagoshima Pref.: 2♀, Minami Kyushu-shi, Kawabe-cho, 26.Feb.2007, K. Ishii leg. (NMST-Ar.14585, identified as H. mogera); 1♀, Minamisatsuma-shi, Kasasa-cho; 9.Dec.2007, K. Ishii leg. (NSMT-Ar.14513).

This species is closely related to N. terrestris and N. silvicola. Male of N. brevipes can be distinguished from male of the latter two species by the presence of two distal processes of paracymbium (Di-I–II), a sharper radical apophysis (Ra), and a thinner median process of conductor (Cm) (vs a single, sharper Di, a stockier Ra, and a thicker Cm in N. terrestris and N. silvicola). (Figs 5A–D, 7A–C cf. Figs 6A–D, 7E–G, 8A–D, 10A–C). In addition, the origin of the embolus (E) from the radix is located in a different position than in N. terrestris (4:30 o’clock in N. brevipes vs 6:00 o’clock in N. terrestris) (Figs 5A, 7A cf. Figs 6A, 7E).

Figure 5. 

Nesticella brevipes A male palp (paratype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (holotype), ventral view F same, female from Kyushu G vulva, dorsal view H habitus of male (old specimen from Kyushu); I habitus of female (specimen from Shikoku); J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 1.0 mm (H, I).

Figure 6. 

Nesticella terrestris A male palp (one of the topotypes), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (topotype), ventral view F same after dissection, shape variation G vulva, dorsal view H habitus of male (topotype) I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 1.0 mm (H, I).

Figure 7. 

Genitalia of Nesticella brevipes and N. terrestris A male palp of N. brevipes, ventral view B same, retrolateral view C detail or paracymbium, dorsal view E female epigyne, ventral view E male palp of N. terrestris, ventral view F same, retrolateral view C detail or paracymbium, dorsal view H female epigyne, ventral view. Abbreviations: Cl – lobe of conductor; Cm – median process of conductor; Co – copulatory opening; Cp – prolateral process of conductor; Cr – retrolateral process of conductor; Di I–II – distal process(es) I and II of paracymbium; Do – dorsal process of paracymbium; E – embolus; P – paracymbium; Ra – radical apophysis; Rx – radix; S – spermatheca; Sc – scapus; Sd – sperm duct; St – subtegulum; Te – tegulum; Ve I–II – ventral processes I and II of paracymbium. Scale bars: 0.2 mm.

Figure 8. 

Nesticella silvicola sp. nov. A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (one of the paratypes), ventral view F same, from shape variation G vulva, dorsal view H habitus of male I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 1.0 mm (H, I).

Female of N. brevipes can be separated from female of N. terrestris and N. silvicola by the slimmer scapus (Sc), approximately as long as wide, usually with a more rounded posterior margin (vs a larger Sc, ~ 1.5–2.0× wider than long, having a flatter posterior margin in N. terrestris and N. silvicola) (Figs 5E, F, 7D cf. Figs 6E, F, 7H, 8E, F, 10D). In addition, N. brevipes shows wider spermathecae (S) than the diameter of the copulatory ducts (Cd) (vs same diameter of Cd in N. terrestris and N. silvicola) and internal ducts with a more convoluted and irregular trend (vs more straight ducts in N. terrestris or strongly bent in the middle in N. silvicola both with less clear coils). (Figs 5E–G cf. Figs 6E–G, 8E–G). In addition, N. brevipes is generally smaller is size than N. terrestris (females 1.76–2.50 vs 2.31–3.30, see also Fig. 17A, B).

(paratype). Habitus as in Fig. 5H. Total length 1.94. Prosoma 1.02 long, 0.87 wide. Carapace rounded, uniformly brown-yellowish with borders and central area slightly darker. Cervical groove and fovea distinct. Chelicerae, labium, maxillae, and sternum of the same uniform color as carapace. Eyes well developed. Eyes measurements: AME = 0.03, ALE = 0.06, PME = 0.07, PLE = 0.07, AME–ALE = 0.04, ALE–PLE = 0.00. Legs uniformly pale yellowish. Legs measurements: I 7.28 (2.04, 0.47, 1.92, 2.04, 0.81), II 5.70 (1.70, 0.43, 1.44, 1.45, 0.68), III 4.23 (1.30, 0.38, 0.96, 1.00, 0.59), IV 5.56 (1.86, 0.43, 1.51, 1.18, 0.58). Opisthosoma greyish with large black marks on dorsal and frontal sides.

Male palp as in Figs 5A–D, 7A–C. Cymbium relatively short, covered with sparse setae, several thicker setae on distal-prolateral margin (Fig. 5D). Paracymbium with 2 hook-like distal processes (Di-I–II), 2 ventral processes (Ve-I–II), and a single dorsal apophysis (Do). Distal process I (Di-I) thick, headed antero-retrolaterally; distal process II (Di-II) slimmer and sharper, headed retrolaterally; ventral process I (Ve-I) short and stocky, headed internally; ventral process II (Ve-II) long and lobated, headed internally; dorsal apophysis (Do) lobated, wide and flat (Figs 5A–D, 7A–C). Embolus (E) long and filiform, origin of embolus positioned at ~ 4:30 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, triangular with a rather sharp tip. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of the conductor (Cp) flat, ribbon-like, headed counterclockwise and wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved inside. Median process of conductor (Cm) tiny and slim, strongly sclerotized with a ribbon-like lobe wrapped around its prolateral side (Figs 5A–C, 7A, B).

(holotype). Habitus (fresh specimen from Shikoku) as in Fig. 5I. Total length 2.24. Prosoma 1.02 long, 0.92 wide. Cephalic area as in Fig. 5J. Carapace piriform. Eyes measurements: AME = 0.02, ALE = 0.06, PME = 0.05, PLE = 0.06, AME–ALE = 0.05, ALE–PLE = 0.00. Coloration and other details as in male. Legs yellowish with darker annulation on femur and tibia. Legs measurements as follows: I 6.55 (1.88, 0.46, 1.74, 1.66, 0.81), II 5.07 (1.52, 0.40, 1.24, 1.21, 0.70), III 3.85 (1.20, 0.30, 0.85, 0.91, 0.59), IV 5.23 (1.67, 0.43, 1.31, 1.17, 0.65).

Epigyne and vulva as in Figs 5E–G, 7D. Scapus (Sc) short and stumpy, approximately as long as wide, ending with a rounded, convex posterior margin (Figs 5E, F, 7D). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as a narrow V. Copulatory ducts (Cd) short, straight, and thick, slightly divergent from each other. Insemination ducts thin, coiled around the copulatory ducts. Spermathecae (S) rounded, slightly wider than copulatory ducts, separated from each other by ~ 2× their diameter (Fig. 5G).

Male (based on 3 specimens): total length: 1.94–2.31, prosoma length: 1.02–1.17, prosoma width: 0.87–0.99. Female (based on 10 specimens): total length: 1.76–2.50, prosoma length: 0.90–1.15, prosoma width: 0.81–0.99.

Western Japan (Shikoku, Kyushu, western Honshu?), China? (Fig. 16A). The easternmost limit of this species in Japan seems to be located in the Kansai area where it apparently overlaps with the distribution of N. terrestris (Fig. 16A). The precise boundaries between these two species remain unclear. All samples and published drawings of N. brevipes from China, Korea, and Russian Far East checked by us refer to different species of Nesticella. In lack of clear records, the presence of this species outside Japan remains unconfirmed although it seems unlikely. See also “remarks on misidentifications” for additional information.

Nesticella brevipes can be found in humid and shadowed environments such as undergrowth of deciduous and evergreen forests growing in narrow valleys, vegetated cliffs, screes, caves, and artificial tunnels. This species builds simple scaffold webs in empty spaces among the leaf litter, between rocks or in the crevices in the walls and on the floor of caves. In subterranean environments we collected this species in both the twilight and the dark zones.

Like many other nesticid species N. brevipes shows a certain degree of intraspecific variation in the shape of genitalia and in particular in the shape of the scapus of the female epigyne. Some individuals from Shikoku Is. (e.g., from Kikuchi Keikoku Gorge), and especially populations from the Kansai area, show a more squared scapus with the posterior margin more flattened than normal. A high degree of intraspecific genetic divergence (7.6%) is also observed between the population living in Shikoku Is. and Kyushu Is.

Nesticella brevipes was first described and illustrated by Komatsu (1940) based on specimens from Ryuga-do cave in the island of Shikoku but wrongly identified as Theridion pilula (= Phoroncidia pilula (Karsch, 1879), Fam. Theridiidae Sundevall, 1833). Yaginuma (1970: p. 386–388, figs 1, 2) recognized the species as new to science and described it based on specimens from the same cave. Nevertheless, he misidentified the male of the closely related N. terrestris thus reporting under N. brevipes a mix of specimens from the two species (Yaginuma 1970: p. 388, 390). Two years later Yaginuma (1972: p. 619–621), in his revision of short-legged nesticids from Japan, synonymized N. terrestris with N. brevipes although it recognized them as belonging to different morpho-groups based on the morphology of the male palp and female epigyne. The outcome of our study, based on both morphological and molecular evidence, clearly supports the original separation of N. brevipes and N. terrestris as two distinct species.

Since the time of its description Nesticella brevipes “sensu lato” has been frequently recorded by Japanese or foreign authors, in Japan and in other surrounding countries (World Spider Catalog 2023, see Shinkai et al. 2022 for the Japanese records). Nevertheless, due to the previous synonymization of N. terrestris with N. brevipes, it is difficult to understand to which species these records refer without directly checking the genitalia of the specimens. Thus, in this work we considered only the records of N. brevipes which samples have been directly examined by us or of which clear published drawings of genitalia were available. Based on the examined material we confirm the presence of N. brevipes in the island of Kyushu and Shikoku and in the Kansai area. We could not check any specimen from the Chugoku area thus the presence of this species in the western part of the Honshu Island, although possible, still needs to be properly confirmed. All records from central-eastern Honshu examined by us refer instead to the similar N. terrestris (see Fig. 16A). Yaginuma (1970, 1972) cited the presence of an unusual population of N. brevipes inhabiting some caves in Mie Prefecture (e.g., Fubonji-do cave). These specimens show partially reduced eyes (Yaginuma 1970: fig. 10) and, apparently, morphological characters of palp and epigyne mixed between those of N. brevipes and N. terrestris (Yaginuma 1972: p. 620, fig. 3). We did not have the opportunity to examine these specific specimens; however, other samples collected in both epigean and hypogean environments in Mie Pref. and checked by us refer to the similar N. terrestris. It is possible that the Nesticella from Fubonji-do cave represent a different and still undescribed troglobitic species. Irie (1981), in his work on cave spiders from Kyushu, illustrate a population of N. brevipes from the Kikuchi Keikoku Gorge, northern Kumamoto Pref., which female show a wide and squared scapus (Irie 1981, figs 2, 3). These specimens were examined by us and, although some individuals have the scapus more squared and sometimes wider than usual, both males and female show the diagnostic characters of N. brevipes.

Concerning the records outside Japan, specimens of N. brevipes from Kuril Is. (Marusik and Crawford 2006) were inspected by us and they refer to N. terrestris. We did not have the possibility to check samples from Korea, nevertheless none of the published drawings of Korean specimens show the diagnostic characters of N. brevipes. Based on the shape of the epigyne they clearly refer to H. mogera (cf. Figs 1A–G, 4A–D vs Paik 1996: figs 6, 9, 10) or to other species of Nesticella of the N. brevipes group, including possibly N. terrestris (cf. Figs 5A–G, 7A–D vs Figs 6A–G, 7E–H vs Paik 1996: figs 7, 8 vs Namkung 2002: fig. 80a, b vs Kim and Lee 2018: fig. 27b, c). On the basis of these observations, we consider the presence of N. brevipes in Korea unlikely.

During his previous studies, the first author had the occasion to examine several Nesticella specimens from China identified as N. brevipes and preserved in the collections of the Chinese Academy of Sciences, Beijing. All these specimens were revealed to be misidentifications of other endemic Nesticella or Howaia species. For example, the specimens determined as N. brevipes by Zhang and Li (2013) were recognized by the first author as H. huomachongensis (Lin, Ballarin & Li, 2016). The drawing of the male palp of N. brevipes from Zhejiang, China, published in Song et al. (1999) do not allow a clear identification of the species, it may refer to N. brevipes as well as another similar Chinese species of the N. brevipes group which was not yet described at the time of the publication of the book. Considering such circumstances, the presence of N. brevipes in China is unlikely but needs to be confirmed.

Japan, Tokyo Pref., Mt. Kagenobuyama.

Japan: Honshu Is.: Iwate Pref.: 1♀, Iwate-gun, Kuzumaki-machi, 4.Aug.1995, H. Okawa leg. (NSMT-Ar.11299, identified as N. brevipes); Miyagi Pref.: 1♂, 1♀, Minamisanriku-cho, Mt. Tatsugane, 21.July.2013, A. Tanikawa leg. (MNHAH); Akita Pref.: 1♀, Akita-shi, Shimokitateyanagitate, Akahira, 18.Jul.2005, A. Fukushima leg. (NSMT-Ar.17417, identified as N. brevipes); Yamagata Pref.: 3♀, Oguni-machi, Tamagawanakazato, 18.July.2010, A. Tanikawa leg. (MNHAH); 2♀, Nukumidaira, 18.July.2010, A. Tanikawa leg.; 1♀, Kotamagawa, 19.July.2010, A. Tanikawa leg. (MNHAH); 1♀, Sakata-shi, Tamasudarenotaki Waterfall, 38.99706°N, 140.05332°E, 27.Aug.2019, Y. Suzuki leg. (YSPC); Ibaraki Pref.: 1♀, Tsukuba-shi, Oda, Mt. Hokyo-san, 36.15260°N, 140.11853°E, 22.Aug.2017, Y. Suzuki leg. (YSPC); 1♂, 1♀, Tsukuba-shi, Mt. Tsukuba, 36.22662°N, 140.09885°E, 29.Jun.2019, Y. Suzuki leg. (YSPC); Tochigi Pref.: 1♀, Imaichi-shi, Iwasaki, 12.Aug.1990, A. Tanikawa leg. (MNHAH); 1♀, Nikko-shi, 7.Jul.1996, Y. Suganami leg. (NSMT-Ar.17205, identified as N. brevipes); Saitama Pref.: 1♂, 2♀; Iruma-gun, Motoyama, near Kamakita cave, Aza-ana cave, 11.Aug.1974, leg. Unknown (FBPC); 3♂, Hiki-gun, Ogawa-machi, Kami-furutera, Furutera-do cave, 6.Jul.2019, T. Hiramatsu leg. (FBPC); 1♂, 6♀, Chichibu-shi, Kuroya, Iwane-do cave, 36.055145°N, 139.114867°E, 06.Nov.2022, T. Nagai leg. (TNPC); Chiba Pref: 1♂, Kamogawa-shi, Kiyosumi, 35.13982°N, 140.17725°E, 20.Feb.2020, Y. Suzuki leg. (YSPC); Tokyo Pref.: 1♀ (holotype), Mt. Kagenobuyama, 20.Dec.1968, E. Shinkai leg. (epigyne dissected and not present in the vial) (NMST-Ar.72); 1♂, 4♀ (topotypes, ~ 3 km Est of the type locality area of the species), Hachioji-shi, Hachioji, trail near the Hachioji castle ruins, 339 m, scree in a narrow valley near a temporary creek, 35.64654°N, 139.25175°E, 31.May.2021, F. Ballarin leg. (FBPC); 1♂, 1♀, Hachioji-shi, Mt. Jinba, 27.May.1984, H. Ono leg. (NSMT-Ar.13401, identified as N. brevipes); 1♀, Okutama-machi, Kaniwasawa, 35.83906°N, 139.07345°E, 27.Jun.2020, Y. Suzuki leg. (YSPC); 1♀, Nishitama-gun, Nippara, near Ichiishiyama Shrine, 1015 m, leaf litter in a beech forest, 35.85506°N, 139.03513°E, 5.May.2022, F. Ballarin leg. (FBPC); Kanagawa Pref.: 1♂, Kawasaki-shi, Tama-ku, Ikuta Ryokuchi, 29.Jun.1991, M. Ban leg. (NSMT-Ar.10062, identified as N. brevipes); 1♀, Atsugi-shi, Nanasawa, 17.Apr.1997, M. Ban leg. (NSMT-Ar.10814, identified as N. brevipes); Fukui Pref.: 1♀, Onyu-gun, Natashou, Nagatani, 30.Jul.2002, K. Kumada leg. (NSMT-Ar.15214, identified as N. brevipes); Shizuoka Pref.: 1♂, 8♀, Tagata-gun, Amagiyugashima-cho, Mt. Ichiyama, 14.Feb.1983, K. Kumada leg. (NSMT-Ar.17762, identified as N. brevipes); 2♀, Kamo-gun, Higashiizu, Mt. Amagi, 18.Oct.1986, A. Tanikawa leg. (MNHAH); 2♀, Fujinomiya-shi, Myojoyama Park, 17.Nov.2014, A. Tanikawa leg. (MNHAH); 1♀, Fujinomiya-shi, Hitoana, Shin-ana Cave (新穴), long and humid lava cave (temp: 11.7 °C, hum: 95.3%), 35.36406°N, 138.59478°E, 725 m, 3.Dec.2022, F. Ballarin leg. (FBPC); 2♀, Hamamatsu-shi, Tenryu-ku, Ryokukeidai, 34.86801°N, 137.79494°E, 2–3.Jan.2018, Y. Suzuki leg. (YSPC); 1♀, Susono-shi, Iwanami, Iwanami Fuketsu Wind Cave (岩波風穴), warm and humid lava cave (temp: 18.9 °C, hum: 99.9%), 35.21835°N, 138.92003°E, 255 m, 2.Dec.2022, F. Ballarin leg. (FBPC); Aichi Pref.: 1♀, Toyohashi-shi, Suse-cho, near the entrance of Susenoja-ana cave (嵩山蛇穴), 34.79678°N, 137.48575°E, litter of a mixed forest, 29.IX.2019, F. Ballarin leg. (FBPC); Mie Pref.: 2♀, Ise-shi, Ujitachi-cho, Naigu, Ise Jingu shrine, 8.Nov.2003, K. Kumada leg. (NSMT-Ar.14059); 1♂, 1♀, Kiya, Koumori-ana (こうもり穴), 27.Sep.–10.Oct.1980, Y. Terumi leg. (OMNH); Russia: Sakhalin Oblast: Moneron Is.: 1♂, 1♀, 23.Aug.2001, Y.M. Marusik leg. (YMPC, identified as N. brevipes).

This species is closely related to N. brevipes and N. silvicola. But generally larger in size than the latter two species (females 2.31–3.30 vs 1.76–2.50 in N. brevipes and 1.84–1.94 in N. silvicola, see also Fig. 17A, B). Male of N. terrestris can be distinguished from male of N. brevipes by the presence of a single, sharper distal process of paracymbium (Di), a stockier radical apophysis ending with a rounded tip (Ra), and a thicker median process of the conductor (Cm) (vs two Di, a sharper Ra ending with a pointy tip, and a thinner Cm in N. brevipes). (Figs 6A–D, 7E–G cf. Figs 5A–D, 7A–C). It can be separated from male of N. silvicola by the sharper distal process of paracymbium (Di), the stockier and rounder radical apophysis (Ra), and by the thinner ventral process II of paracymbium (Ve-II), (vs stockier Di, sharper Ra, and wider Ve-II in N. silvicola). (Figs 6A–D, 7E–G cf. Figs 8A–D, 10A–C). In addition, the origin of the embolus I from the radix is located in a different position than in the other two species (6:00 o’clock in N. terrestris vs 4:30 o’clock in N. brevipes and N. silvicola) (Figs 6A, 7E cf. Figs 5A, 7A, 8A, 10A).

Figure 9. 

Nesticella insulana sp. nov. A male palp (holotype), ventral view B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne (one of the paratypes), ventral view F same, from shape variation G vulva, dorsal view H habitus of male I habitus of female J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 1.0 mm (H, I).

Figure 10. 

Genitalia of Nesticella silvicola sp. nov. and N. insulana sp. nov. A male palp of N. silvicola sp. nov., ventral view B same, retrolateral view C detail or paracymbium, dorsal view E female epigyne, ventral view E male palp of N. insulana sp. nov., ventral view F same, retrolateral view C detail or paracymbium, dorsal view H female epigyne, ventral view. Abbreviations: Cl – lobe of conductor; Cm – median process of conductor; Co – copulatory opening; Cp – prolateral process of conductor; Cr – retrolateral process of conductor; Di I–II – distal process(es) I and II of paracymbium; Do – dorsal process of paracymbium; E – embolus; P – paracymbium; Ra – radical apophysis; Rx – radix; S – spermatheca; Sc – scapus; Sd – sperm duct; St – subtegulum; Te – tegulum; Ve I–II – ventral processes I and II of paracymbium. Scale bars: 0.2 mm.

Female of N. terrestris can be separated from female of N. brevipes by the thicker and more squared scapus ~ 1.5–2× longer than wide and having a flat posterior margin (vs a slimmer scapus approximately as long as wide, with a rounded posterior margin in N. brevipes) (Figs 6E, F, 7H cf. Figs 5E, F, 7D). In addition, N. terrestris shows spermathecae (S) which diameter is approximately as wide as the copulatory ducts (vs S wider than copulatory ducts in N. brevipes) and straight internal ducts with a regular trend and few visible coils (vs ducts with a more irregular trend and more visible coils in N. brevipes). (Fig. 6E–G cf. Fig. 5E–G). Female of N. terrestris can be separated from female of N. silvicola by the more lobated scapus (Sc) with rounder lateral margins and straight internal ducts (vs more squared lateral margins and strongly bent internal ducts in N. silvicola) (Figs 6E–G, 7H cf. Figs 8E–G, 10D).

(one of the topotypes). Habitus as in Fig. 6H. Total length 2.54. Prosoma 1.22 long, 1.18 wide. Carapace rounded, uniformly yellowish with borders and central area slightly darker. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.06, ALE = 0.09, PME = 0.09, PLE = 0.09, AME–ALE = 0.06, ALE–PLE = 0.01. Chelicerae, labium, maxillae, and sternum of the same color as carapace. Legs yellowish with darker annulation on femur, patella, and tibia. Legs measurements as follows: I 7.07 (2.03, 0.47, 1.99, 1.77, 0.81), II 5.56 (1.64, 0.47, 1.41, 1.31, 0.73), III 4.55 (1.39, 0.41, 1.09, 1.07, 0.59), IV 6.12 (1.89, 0.47, 1.61, 1.48, 0.67). Opisthosoma greyish with large black marks on dorsal and lateral sides.

Male palp as in Figs 6A–D, 7E–G. Cymbium relatively short, covered with sparse setae, several thicker setae on distal-prolateral margin (Fig. 6D). Paracymbium with a single distal process (Di), two ventral processes (Ve-I–II), and a dorsal apophysis (Do): distal process (Di) thick, hook-like when observed laterally, with a sharp tip headed ventrally and retrolaterally; ventral process I (Ve-I) stocky and blunt, headed internally; ventral process II (Ve-II) long, headed internally; dorsal apophysis (Do) lobated, wide and flat (Figs 6A–D, 7E–G). Embolus (E) long and filiform, origin of embolus positioned ~ 6:00 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, triangular, ending with a rounded tip. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of the conductor (Cp) flat, ribbon-like and headed counterclockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved inside. Median process of conductor (Cm) thick and strongly sclerotized, spine-like, ending sharp, with a ribbon-like lobe wrapped around its prolateral side. (Figs 6A–C, 7E, F).

(one of the topotypes). Habitus as in Fig. 6I, 15B. Total length 2.95. Prosoma 1.55 long, 1.16 wide. Cephalic area as in Fig. 6J. Carapace piriform. Eyes measurements: AME = 0.06, ALE = 0.09, PME = 0.09, PLE = 0.09, AME–ALE = 0.07, ALE–PLE = 0.00. Coloration and other details as in male. Legs measurements as follows: I 7.85 (2.32, 0.61, 2.13, 1.91, 0.88), II 6.01 (1.79, 0.53, 1.52, 1.41, 0.76), III 4.72 (1.46, 0.44, 1.04, 1.11, 0.67), IV 6.65 (2.19, 0.53, 1.72, 1.47, 0.74). Epigyne and vulva as in Figs 6E–G, 7H. Scapus (Sc) short and stumpy, rectangular, laterally elongated, ~ 1.5–2.0× wider than long, ending with a flat or slightly curved posterior margin (Figs 6E, F, 7H). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, V shaped. Copulatory ducts (Cd) short, straight, and thick, strongly diverging from each other. Insemination ducts thin, coiled around the Cd. Spermathecae (S) small and rounded, separated from each other by ~ 2–2.5× their diameter (Fig. 6G).

Male (based on 5 specimens): total length: 2.01–2.54, prosoma length: 1.05–1.25, prosoma width: 0.95–1.18. Female (based on 15 specimens): total length: 2.31–3.30, prosoma length: 1.03–1.45, prosoma width: 0.94–1.21.

Japan (Hokkaido, central-eastern Honshu, western Honshu?), Russian Far East (Sakhalin and Kuril Is.), Korea? (Fig. 16A). The presence of this species in western Honshu and Korea needs confirmation. See also “remarks on misidentification” for additional notes on the distribution of N. terrestris.

Nesticella terrestris is found in humid and shadowed habitats, including forest leaf litter, under rotten logs and stones, vegetated cliffs, screes, and caves, both limestone and lava caves. This species builds simple scaffold webs in empty spaces among leaf litter and in rock recesses.

This species shows some degree of variation in size and in the shape of the epigyne, different individuals having a slightly wider or slightly narrower scapus. The posterior margin is usually straight but it might be also slightly concave or slightly convex depending by the individuals. Specimens from the Kansai area seem to have a general smaller size and a scapus proportionally narrower than those of other populations.

Nesticella terrestris was originally described by Yaginuma (1970: p. 387, 390, 391, figs 3–5) on the basis of a female collected from the Tokyo area. The author misidentified the male describing a male of H. mogera as a paratype of N. terrestris (Yaginuma 1970: p. 387, 391, fig. 8). An additional male from Gifu was also wrongly identified as N. brevipes and illustrated but not described (Yaginuma 1970: p. 387, fig. 9). The other records reported in the same work are probably a mix of the three species (Yaginuma 1970: p. 392). Nesticella terrestris was subsequently synonymized with N. brevipes by Yaginuma himself (1972: p. 619–621) believing that the differences in the shape of male palp and epigyne were part of the intraspecific variability of the species. Both the morphological and molecular results illustrated in our study clearly show that N. terrestris and N. brevipes are in fact two distinct species. Based on these conclusions the resurrection of N. terrestris as a valid species is herein proposed. Accordingly, we describe and illustrate for the first time the male of N. terrestris based on specimens collected from the type locality of the species. Due to the synonymization of N. terrestris with N. brevipes the published records of these two species are currently mixed. In this study we considered only the records that we could directly confirm on the basis of published drawings or checked samples. Based on our material all records from central and eastern Honshu up to Hokkaido refer to N. terrestris, while N. brevipes can be found in the islands of Honshu, Kyushu, and part of the Kansai area. (Fig. 16A). Due to the lack of specimens from western Kansai and Chugoku areas we cannot confirm the presence of N. terrestris in western Honshu although it seems plausible. Specimens of N. brevipes from Kuril Is. (Marusik and Crawford 2006) were checked by us and confirmed as N. terrestris. The illustrated specimens of N. brevipes from Korea (e.g., Kim and Lee 2018, fig. 11a–c) show close similarities with the palp and epigyne of N. terrestris rather than N. brevipes and possibly refer to the this or another closely related species (cf. Figs 5A–G, 7A–D vs Figs 6A–G, 7E–H vs Kim and Lee 2018: fig. 11A–C). The presence of N. terrestris in Korea needs to be properly verified directly examining the specimens.

Figure 11. 

Nesticella occulta sp. nov. A habitus of female (holotype) B cephalic area of female, frontal view C female epigyne, ventral view D same, shape variation E vulva, dorsal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; Id – insemination duct; S – spermatheca; Sc – scapus. Scale bars: 1.0 mm (A, C); 0.2 mm (B, D, E).

♂ Holotype: Japan: Kagoshima Pref., Yakushima Is.: Koseda, Nagamine, 29.Mar.2023, S. Konishi leg. (NSMT-Ar 25254).

Paratypes: Japan: Kagoshima Pref., Yakushima Is.: 1♀, Koseda, 190 m, broadleaf forest litter on a gentle slope, 30.38286°N, 130.62455°E, 24.Sep.2021, F. Ballarin leg. (RMUF); 2♀, Isso, 130 m, broadleaf forest litter bordering a sugi plantation near a river, 30.43615°N, 130.48129°E, 27.Sep.2021, F. Ballarin leg. (NSMT-Ar 25255); 1♀, Miyanoura, 15.July.1990, A. Tanikawa leg. (FBPC); 1♀, Miyanoura, 341 m, humid broadleaf forest litter in a humid valley near a creek, 30.39696°N, 130.55584°E, 27.Sep.2021, F. Ballarin leg. (FBPC); 1♀, Anbo, 224 m, broadleaf forest litter, 30.28375°N, 130.61619°E, 27.Sep.2021, F. Ballarin leg. (FBPC); 1♀ Jhonji-dake, 18.Feb.2023, S. Konishi leg. (NSMT-Ar 25256)

The specific name is derived from the Latin adjective silvicolus (= inhabiting woods, sylvan). It refers to the habitat of the species, living in the forests of Yakushima Is.

This species is closely related to N. brevipes and N. terrestris. Male of N. silvicola sp. nov. can be distinguished from male of N. terrestris by the stockier distal process of paracymbium (Di), the sharper radical apophysis (Ra), and by the wider ventral process II of paracymbium (Ve-II), (vs sharper Di, rounder Ra, and thinner Ve-II in N. terrestris). (Figs 8A–D, 10A–C cf. Figs 6A–D, 7E–G). In addition, the origin of the embolus (E) from the radix is located in a different position in the two species (4:30 o’clock in N. silvicola vs 6:00 o’clock in N. terrestris) (Figs 8A, 10A cf. Figs 6A, 7). Male of the new species can be easily separated from male of N. brevipes by the single distal process of paracymbium (Di), a wider radical apophysis (Ra), and a thicker median process of conductor (Cm) (vs two Di, a slimmer Ra, and a thinner Cm in N. brevipes). (Figs 8A–D, 10A–C cf. Figs 5A–D, 7A–C).

Female of N. silvicola sp. nov. can be distinguished from female of the other Japanese congeners of the N. brevipes group, by the general shape of genitalia, having a short scapus (Sc) with a flat distal margin, more squared lateral margins and strongly bent internal ducts (vs a longer and lobated Sc with straight ducts in N. brevipes, a more lobated scapus with rounder distal margins and straight internal ducts in N. terrestris, or a narrower and more trapezoidal scapus in N. insulana sp. nov. (Figs 9E–G, 10F cf. Figs 5E–G, 6E–G, 7D, H, 8E–G, 10D). The smaller size further allows a quick separation of N. silvicola sp. nov. from N. terrestris (females 1.84–1.94 vs 2.31–3.30).

(holotype). Habitus as in Fig. 8H. Total length: 1.91. Prosoma 0.97 long, 0.86 wide. Carapace rounded, yellowish with slightly darker margins and central area. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.04, ALE = 0.08, PME = 0.08, PLE = 0.08, AME–ALE = 0.03, ALE–PLE = 0.00. Chelicerae, labium, maxillae, and sternum of same color as carapace. Legs yellowish with slightly darker annulation on distal femur, tibia, and metatarsus. Legs measurements: I 5.63 (1.60, 0.43, 1.48, 1.48, 0.64), II 4.28 (1.25, 0.38, 1.05, 1.06, 0.54), III 3.91 (1.00, 0.31, 0.82, 0.81, 0.47), IV 4.58 (1.44, 0.41, 1.16, 1.13, 0.44). Opisthosoma greyish with couples of slightly darker marks on anterior and dorsal side gradually merging to each other toward the posterior side.

Palp as in Figs 8A–D, 10A–C. Cymbium relatively short, covered with sparse setae, some thicker setae on distal-prolateral margin (Fig. 8D). Paracymbium with a single distal process (Di), two ventral processes (Ve-I–II), and a dorsal apophysis (Do): distal process (Di) stumpy, headed ventrally and retrolaterally, hook-like when observed laterally; ventral process I (Ve-I) sharp and slim, headed internally; ventral process II (Ve-II) lobated, headed internally; dorsal apophysis (Do) lobated, wide and flat (Figs 8A–D, 10A–C).Embolus (E) long and filiform, origin of embolus positioned at ~ 4:30 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, wide and stumpy, triangular, ending with a rounded tip. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of conductor (Cp) flat, ribbon-like and headed counterclockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved inside. Median process of conductor (Cm) thick and strongly sclerotized, spine-like, ending blunt, with a ribbon-like lobe wrapped around its prolateral side. (Figs 8A–C, 10A, B).

(one of the paratypes). Habitus as in Fig. 8I. Total length: 1.87. Prosoma 0.88 long, 0.78 wide. Cephalic area as in Fig. 8J. Eyes measurements: AME = 0.04, ALE = 0.08, PME = 0.08, PLE = 0.08, AME–ALE = 0.03, ALE–PLE = 0.00. Coloration and other details as in male. Legs measurements: I 4.65 (1.33, 0.40, 1.21, 1.10, 0.61), II 3.68 (1.10, 0.37, 0.86, 0.82, 0.53), III 2.09 (0.89, 0.30, 0.62, 0.63, 0.46), IV 3.96 (1.22, 0.33, 1.02, 0.88, 0.53).

Epigyne and vulva as in Figs 8E–G, 10D. Scapus (Sc) very short and wide, rectangular, ~ 2.5× wider than long, ending with a flat posterior margin slightly concave in the center (Figs 8E, F, 10D). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as 2 angled brackets pointing towards each other. Copulatory ducts (Cd), short and thick, bent in the central trait, proximal part of ducts heading slightly internally, distal part heading laterally before reaching spermathecae. Insemination ducts (Id) thin, coiled around copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 1.5× their diameter (Fig. 8G).

(based on 5 females). Total length: 1.84–1.94, prosoma length: 0.86–0.99, prosoma width: 0.78–0.84.

Known only from Yakushima Is. in western Japan (Fig. 16B).

Nesticella silvicola sp. nov. inhabits the shadowed and humid broadleaf and mixed forests covering the mountain slopes in Yakushima Is. This species builds simple scaffold webs in the empty spaces and recesses between the leaf litter and under rotten logs.

♂ Holotype: Japan: Okinawa Pref., Yonaguni-jima Is.: Mantabaru Forest Park (満田原森林公園), 54 m, humid forest litter in a narrow valley, 24.45652°N, 122.97692°E, 3.Mar.2021, K. Eguchi leg. (NSMT-Ar 25257).

Paratypes : 4♀, same locality and date as the holotype, K. Eguchi leg. (NSMT-Ar 25258); 5♀, same locality and date, 112 m, 24.45678°N, 122.97675°E, F. Ballarin leg. (FBPC).

1♂ subad., same locality and date as the holotype, 115 m, humid forest litter, 24.45660°N, 122.97584°E, F. Ballarin leg. (FBPC); 1♀ subad., 54 m, humid forest litter in a small valley near route 216, 24.44740°N, 122.96827°E, 04.Mar.2021, F. Ballarin leg. (FBPC).

The specific name is derived from the Latin adjective insulanus (= islander). It refers to the distribution of the species, limited to the island of Yonaguni-jima.

The new species is closely related to Nesticella odonta (Chen, 1984) from Zhajinag Province, China. Male of the new species can be distinguished from male of N. odonta by the wider distal process I of paracymbium (Di-I), the smaller and blunter distal process II (Di-II), and by the more curved ventral process II (vs thinner and sharper Di-I, wider Di-II, and straighter Ve-II in N. odonta) (Figs 9A, B, D, 10E–G cf. Lin et al. 2016: figs 24A, B, D). Female of N. insulana sp. nov. can be separated from female of N. odonta by the narrower, longer, and more arrow-like scapus (Sc) of the epigyne (vs wider, more trapezoidal, and shorter scapus in N. odonta) (Figs 9E–G, 10H cf. Lin et al. 2016: fig. 25E–G). The general shape of genitalia in both male and female allows to easily discern N. insulana sp. nov. from all the other Japanese congeners of the N. brevipes group.

(holotype). Habitus as in Fig. 9H. Total length 1.81. Prosoma 0.91 long, 0.83 wide. Carapace rounded, yellowish with darker areas around borders and central area. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.05, ALE = 0.08, PME = 0.08, PLE = 0.08, AME–ALE = 0.04, ALE–PLE = 0.01. Chelicerae, labium, maxillae, and sternum of same color as carapace. Legs yellowish often with dark annulations on femur, and tibia. Legs measurements as follows: I 5.98 (1.65, 0.43, 1.58, 1.59, 0.73), II 4.35 (1.25, 0.31, 1.13, 1.06, 0.60), III 3.33 (0.98, 0.36, 0.70, 0.76, 0.53), IV 4.67 (1.43, 0.33, 1.19, 1.04, 0.68). Opisthosoma greyish with large dark marks on dorsal and lateral sides.

Male palp as in Figs 9A–D, 10E–G. Cymbium relatively short, 4–6 thicker setae on distal-prolateral margin (Fig. 9D). Paracymbium with 2 distal processes (Di-I, II) and 2 flat, lobated ventral processes (Ve-I–II): distal process I (Di-I) wide and lobated, hook-like when observed laterally, with tip headed ventral-retrolaterally; distal process II (Di-II) short and blunt, headed frontally; ventral process I (Ve-I) shorter, headed anteriorly; ventral process II (Ve-II) long and curved, headed antero-retrolaterally (Figs 9A–D, 10E–I Embolus (E) long and filiform, origin of embolus positioned at ~ 4:00 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, triangular, and sharp, ending with a pointed tip. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of conductor (Cp) flat, ribbon-like, headed counter-clockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved inside, bearing a small sclerotized apophysis (Ca). Median process of conductor (Cm) strongly sclerotized, thin, spine-like ribbon-like, with a ribbon-like lobe wrapped around its prolateral side. (Figs 9A–C, 10E, F).

(one of the paratypes). Habitus as in Fig. 9I. Total length 2.05. Prosoma 0.91 long, 0.84 wide. Cephalic area as in Fig. 9J. Carapace piriform. Eyes measurements: AME = 0.05, ALE = 0.07, PME = 0.08, PLE = 0.08, AME–ALE = 0.04, ALE–PLE = 0.01. Coloration and other details as in male. Legs measurements as follows: I 5.45 (1.61, 0.45, 1.41, 1.33, 0.65), II 3.98 (1.19, 0.41, 0.93, 0.89, 0.56), III 3.04 (0.88, 0.34, 0.67, 0.64, 0.51), IV 4.29 (1.39, 0.40, 1.09, 0.92, 0.49).

Epigyne and vulva as in Figs 9E–G, 10H. Scapus (Sc) short and stumpy, arrow-like, ~ 2× wider than long, with sloped borders and narrower, slightly rounded tip (Figs 9E, F, 10H). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as curly bracket. Copulatory ducts (Cd) thick, strongly bent in middle trait, curving first laterally and then anteriorly before reaching spermathecae. Insemination ducts thin, coiled around copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 1.5× their diameter (Fig. 9G).

Female (based on 5 specimens): total length 1.90–2.57, prosoma length: 0.82–1.05, prosoma width: 0.78–0.93.

Endemic to Yonaguni-jima Is., western Ryukyus. Known only from the type locality (Fig. 16B).

Nesticella insulana sp. nov. inhabits the shadowed and humid forests covering the hills of the central-western area of Yonaguni-jima Island. This species builds simple scaffold webs in the empty spaces among the leaf litter accumulated in narrow valleys, under rotten wood and on vegetated cliffs. Despite several attempted surveys, this species was not collected in other parts of the island.

♀ Holotype: Japan: Okinawa Pref.: Ishigaki-jima Is.: Kabira, Kabirano-ana cave (川平の穴), long and superficial cave with many rocks, in the dark zone of the cave, 24.47384°N, 124.13416°E, 20.Sep.2022, F. Ballarin leg. (NSMT-Ar 25259). Paratypes: 1♀, same locality as the holotype, 1.Apr.2019, K. Uchida leg. (NSMT-Ar 25260); 1♀, same locality, 2.Jan.2022, K. Uchida leg. (RMUF); 2♀, same locality and date as the holotype, F. Ballarin leg. (FBPC).

1♂subad., same locality as the holotype, 16.Oct.2020; 1♂subad., same locality, 2.Jan.2022; 1♂subad., same locality, 28.Mar.2022, all K. Uchida leg. (RMUF).

The specific name derives from the Latin adjective occultus (= hidden, secret). It refers to the troglobitic lifestyle and rarity of the species, hidden in the deep recess of a single cave in Ishigaki-jima Is.

This species closely related to N. kaohsiungensis Lin, Ballarin & Li, 2016 from Taiwan. The new species can be easily distinguished from N. kaohsiungensis by the strongly reduced eyes and the lack of pigmentation and pattern on the opisthosoma (vs eyes well-developed, clear pattern on the opisthosoma and pigmentation present in N. kaohsiungensis) (Fig. 11A, B cf. Lin et al. 2016: fig. 69A, C). In addition, the female of this species can be distinguished from the female of N. kaohsiungensis by the different shape of scapus, lacking a lobated tip (vs ending with a lobated tip in the latter species) (Figs 11C, D, 13F cf. Lin et al. 2016: fig. 69E, F).

Female (holotype). Habitus as in Fig. 11A, 15D. Total length 2.48. Prosoma 1.08 long, 0.93 wide. Carapace piriform, uniformly pale yellowish. Cephalic area as in Fig. 11B. Eyes completely degenerated. Cervical groove and fovea indistinct. Chelicerae uniformly brownish. Labium, maxillae, and sternum pale yellowish as carapace. Legs uniformly pale yellowish. Legs measurements: I 6.36 (2.18, 0.47, 1.48, 1.46, 0.77), II 6.13 (1.97, 0.45, 1.60, 1.42, 0.69), III 4.36 (1.43, 0.38, 0.95, 0.90, 0.70), IV 6.02 (1.94, 0.46, 1.54, 1.32, 0.76). Opisthosoma uniformly greyish, covered by long, sparse hairs.

Epigyne and vulva as in Figs 11C–E, 13F. Scapus (Sc) long and protruding, tongue-like, ~ 2× longer than wide, ending with a rounded tip (Figs 11C, D, 13F). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, V shaped. Copulatory ducts (Cd) short and straight, strongly diverging from each other (Figs 11C–E, 13F) distal trait coiled, reaching spermathecae with 1 coil. Insemination ducts (Id) thin, coiled around the copulatory ducts. Spermathecae (S) small and rounded, separated from each other by ~ 2.5× their diameter (Fig. 11E).

Male. Unknown.

(based on 4 females) Total length: 1.75–2.48, prosoma length: 1.06–1.10, width: 0.92–0.94 wide.

Ishigaki-jima Island. Known only from the type locality (Fig. 16B).

Nesticella occulta sp. nov. lives in the dark zone of the type locality cave characterized by high and stable temperature and humidity (e.g., temp: 25.8 °C, hum: 94.4%) (Fig. 15H). It builds small and simple scaffold-webs among the crevices and empty spaces between the numerous rocks covering the floor of the cave and on the lower part of the cave walls. These spiders appear scattered inside the cave and rather infrequently, suggesting a relatively small population. The compete eyes degeneration, the lack of pigmentation and the presence of the species only in the deepest section of the cave suggest that N. occulta sp. nov. is a true troglobiont. These characteristics as well as the rarity of the species, inhabiting a single cave, make N. occulta sp. nov. a good target for species conservation.

Japan, Okinawa honto Is., Kakinohana,Tamagusuku-son, Yaaji-gama Cave.

Japan: Kagoshima Pref.: Amami-Ōshima Is.: 1♂, 1♀, Amami-shi, Naze, forest litter, 15.Mar.2020, R. Serita leg. (FBPC); Okinoerabu-jima Is.: 1♀, Murauchi Shindō cave (村内新洞), 4.May.2004, H. Tamura leg. (MNHAH); 1♀, China-cho, Ginsuido cave (銀水洞), 27.Apr.2004, H. Tamura leg. (MNHAH); Okinawa Pref.: Okinawa-honto Is.: 2♀, Kunigami-gun, Motobu-cho, Izumi, 216 m, forest litter along the road, 26.63968°N, 127.93916°E, 17.Nov.2020; 1♀, Kunigami-son, Yona, Yambaru Park, 185 m, humid forest litter, 26.74755°N, 128.22347°E, 25.Feb.2021; 1♂, 10♀, same locality, 132 m, 26.75168°N, 128.22227°E, 28.Feb.2021; 2♀, same locality, 206 m, 26.74536°N, 128.22545°E, 28.Feb.2021; 2♀, same locality, 55 m, 26.75803°N, 128.22167°E, 01.Mar.2021, all F. Ballarin leg. (FBPC); 1♂, 1♀, Ogimi-son, Okuni-rindo Pass, 7.Mar.2020, Y. Suzuki leg. (YSPC); Kume-jima Is.: 2♀, Shimajiri-gun, Maja, 95 m, litter in a broadleaf forest, 26.34819°N, 126.80254°E, 18.May.2022, F. Ballarin leg. (FBPC); 1♀, Uegusuku, 263 m, litter in a broadleaf forest, 26.37577°N, 126.76990°E, 18.May.2022, F. Ballarin leg. (FBPC).

Male of Nesticella okinawaensis can be distinguished from male of other Japanese congeners by the short and stocky beak-like median process of conductor (Cm) with a long ventral process (vs a longer, smaller, or thinner Cm, with a smaller or lacking ventral process in other species), by the presence of a long, lobated distal apophysis on the retrolateral process of conductor (Ca) (vs small Ca in N. silvicola sp. nov. or lacking in other species), and by the shape of paracymbium having an elongated distal process I (Di-I) and a lobated and complex distal process II (Di-II) (vs a shorter Di-I, and a missing, simpler, smaller or thinner Di-II in other species) (Figs 12A–D, 13A–C cf. Figs 1A–D, 2A–D, 4A–C, E–G, 5A–D, 6A–D, 7A–C, E–G, 8A–D, 9A–D, 10A–C, E–G). Female of N. okinawaensis is easily distinguished from female of other Japanese species by the shape of the internal copulatory ducts (Cd), thin and convoluted (vs thicker and less convoluted Cd in other species) (Figs 12E–G, 13D cf. Figs 1E–G, 2E–G, 3D, E, 4D, H, 5E–G, 6E–G, 7D, H, 8E–G, 9E–G, 10D, H, 11C–E, 13E, F).

Figure 12. 

Nesticella okinawaensis A male palp, ventral view (specimen from Yambaru) B same, retrolateral view C same, ventro-prolateral view D same, dorsal view E female epigyne, ventral view (specimen from Yambaru) F same after dissection, shape variation (specimen from Amami-Ōshima Is.) G vulva, dorsal view (specimen from Yambaru) H habitus of male (specimen from Amami-Ōshima Is.) I habitus of female (specimen from Yambaru) J cephalic area of female, frontal view. Abbreviations: Cd – copulatory duct; Co – copulatory opening; S – spermatheca; Sc – scapus. Scale bars: 0.2 mm (A–G, J); 0.5 mm (H, I).

Figure 13. 

Genitalia of Nesticella okinawaensis, Howaia subterranea sp. nov., and N. occulta sp. nov. A male palp of N. okinawaensis, ventral view B same, retrolateral view C detail or paracymbium, dorsal view D female epigyne, ventral view; E H. subterranea sp. nov., female epigyne, ventral view F N. occulta sp. nov. female epigyne, ventral view. Abbreviations: Ca – apophysis of the retrolateral process of conductor; Cl – lobe of conductor; Cm – median process of conductor; Co – copulatory opening; Cp – prolateral process of conductor; Cr – retrolateral process of conductor; Di I–II – distal processes I and II of paracymbium; E – embolus; P – paracymbium; Ra – radical apophysis; Rx – radix; S – spermatheca; Sc – scapus; Sd – sperm duct; St – subtegulum; Te – tegulum; Ve – ventral process of paracymbium. Scale bars: 0.2 mm.

(from Yambaru Park, Okinawa-honto). Habitus as in Fig. 12H. Total length 1.89. Prosoma 1.02 long, 0.90 wide. Carapace rounded, yellowish with dark cephalic area, median stripe, and margins. Cervical groove and fovea distinct. Eyes well developed. Eyes measurements: AME = 0.04, ALE = 0.09, PME = 0.09, PLE = 0.09, AME–ALE = 0.03, ALE–PLE = 0.00. Chelicerae, labium, maxillae, and sternum of the same yellowish color as carapace. Legs yellowish with dark annulation on femur, patella, tibia, metatarsus, and tarsus. Legs measurement: I 5.46 (1.51, 0.40, 1.41, 1.41, 0.53), II 4.68 (1.41, 0.38, 1.17, 1.16, 0.56), III 3.43 (1.07, 0.33, 0.77, 0.83, 0.43), IV 5.15 (1.57, 0.41, 1.39, 1.21, 0.57). Opisthosoma dark grey with whitish dorsal mark on dorsal-anterior side.

Male palp as in Figs 12A–D, 13A–C. Cymbium elongated, five or six robust setae on the distal and distal-prolateral margin (Fig. 12D). Paracymbium with 2 distal processes (Di-I–II) and 1 ventral process (Va). Distal process I (Di-I) long, laterally flattened, slightly bent internally, ending with a small lobated tip; distal process II (Di-II) wide, proximal part laterally flattened, headed frontally, distal part lobated, headed internally bearing 2 small spurs. Ventral process of paracymbium (Va) wide, flat, triangularly shaped. (Figs 12A, B, D, 13A, C). Embolus (E) long and filiform, origin of embolus positioned at ~ 4:30 o’clock on radix (Rx). Radical apophysis (Ra) strongly sclerotized, rectangularly shaped, flat, and stocky with granulated surface. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process (Cp) long and flat, ribbon-like, headed counterclockwise, wrapped around embolus. Retrolateral process (Cr) wide and thick, curved internally, distally bearing a long, lobated apophysis (Ca) and a flat, triangular outgrowth in the central part. Median process of conductor (Cm) beak-like, short and stocky, strongly sclerotized, with a long, strongly sclerotized ventral process (Figs 12A–C, 13A, B).

(from Yambaru Park, Okinawa-honto). Habitus as in Figs 12I, 15E. Total length 1.84. Prosoma 0.87 long, 0.72 wide. Carapace piriform. Cephalic area as in Fig. 12J. Eyes well-developed. Eyes measurements: AME = 0.03, ALE = 0.08, PME = 0.08, PLE = 0.08, AME–ALE = 0.03, ALE–PLE = 0.00. Legs measurements: I 6.13 (1.51, 0.41, 1.36, 1.28, 0.57), II 3.66 (1.09, 0.36, 0.85, 0.83, 0.53), III 2.58 (0.70, 0.31, 0.56, 0.55, 0.46), IV 4.26 (1.33, 0.40, 1.04, 0.98, 0.51). Coloration and other details as in male.

Epigyne and vulva as in Figs 12E–G, 13D. Scapus (Sc) short, rectangular, elongated laterally, ~ 2× wider than long, bearing a flat posterior margin (Figs 12E, F, 13D). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as 2 inverted round brackets. Copulatory ducts (Cd), thin, coiled, reaching the spermathecae after 2 coils. Insemination ducts (Id) thin. Spermathecae (S) small and rounded, separated from each other by ~ 2.5× their diameter (Fig. 12G).

Male (based on 3 males) Total length: 1.85–1.89, prosoma length: 1.01–1.02, width: 0.88–0.90. Female (based on 8 females) Total length: 1.68–2.07, prosoma length: 0.88–0.92, width: 0.79–0.81.

Nesticella okinawaensis is distributed in the islands forming the Central Ryukyu arc (Fig. 16B). The new records for Amami-Ōshima and Okinoerabu-jima islands herein reported extend the known distribution of this species ~ 200 km to the North-East. Currently, N. okinawaensis is recorded from the islands of Amami-Ōshima, Okinoerabu-jima, Okinawa-honto, and Kume-jima (Yaginuma 1979; Tanikawa and Sasaki 1999; and this work) but its presence in other minor islands of the Central Ryukyu is also probable.

Nesticella okinawaensis dwells in humid and shadowed habitats such as caves, narrow valleys, and vegetated cliffs. This species builds simple scaffold webs in empty spaces in the leaf litter or under logs and superficial rocks, as well as in recesses of the walls and floor of caves, usually in the twilight zone.

The general coloration and the dorsal pattern of the opisthosoma appear rather variable in N. okinawaensis, changing among populations living in different areas or different islands or even single individuals. Populations living in the northern area of Okinawa-honto Is. often show a darker pattern, with less clear marks often reduced to a single whitish spot on the dorsal-anterior side (Figs 12I, 15E); populations from Kume-jima Is. often have a whitish continuous stripe along the median line of the opisthosoma, while populations from Amami-Ōshima Is. usually have a general lighter pattern with numerous larger light marks partially fused to each other (Fig. 12H). The shape of scapus also shows minor variability among specimens from different islands with the samples from Kume-jima Is. and Okinoerabu-jima Is. generally having a slightly narrower scapus. A high degree of genetic variation is also observed between population distributed in different islands (e.g., Amami Is.-Kumejima Is. = 7.3–7.8%; Amami Is.-Okinawa Is. = 7.5%; Kumejima Is.-Okinawa Is. = 5.6–6.7%).

Nesticella okinawaensis was provisionally included in the N. brevipes group by Lin et al. (2016) on the basis of published drawings only. Our molecular analysis, and a detailed morphological comparison of this species with the type material of N. brevipes, suggest that N. okinawaensis is in fact far related to the N. brevipes group and it belongs to a distinct clade. In addition, this species seems to have a basal position within the genus Nesticella (Fig. 14). Nevertheless, the phylogeny reconstructed in this work is based on a single gene fragment and includes only a part of the known Nesticella species. Preliminary analysis including more species (e.g., species of the N. phami group) seem to confirm the monophyly of N. okinawaensis although the support of the main nodes decreases substantially. Wider and more detailed molecular and morphological studies including a larger number of species and gene fragments are necessary to confirm the phylogenetic position of N. okinawaensis within Nesticella.

Figure 14. 

Combined phylogenetic tree based on COI gene fragment reconstructed using maximum likelihood (ML) on RAxML and Bayesian inference (BI) on MrBayes. Support at each node denotes the ML bootstrap value (BV) and BI posterior probability (PP). Nodes highly supported by at least one method (BV ≥ 70 or PP ≥ 0.95) are highlighted by a black dot. Branch lengths were scaled concerning the number of substitutions per site. Each species corresponding to monophyletic clades are represented with different branch colors, species from Japan are highlighted with a colored background: red = H. mogera, azure = H. alba sp. nov., yellow = N. occulta sp. nov., violet = N. insulana sp. nov., light green = N. silvicola sp. nov., blue = N. brevipes, orange = N. terrestris, dark green = N. okinawaensis. The tree is rooted using the species Wraios longiembolus. The right lines denote the results of the species delimitation analysis based on morphological (MO) and molecular (ASAP, mPTP, and bPTP) data.

Figure 15. 

Nesticella and Howaia species in life and their natural habitats A female of H. mogera B female of N. terrestris C female of H. alba sp. nov. D female of N. occulta sp. nov. E female of N. okinawaensis F example of the epigean habitat of Nesticella species in the Ryukyus G habitat of H. alba sp nov. (dark zone of Tsuzupisuki-abu cave) H habitat of N. occulta sp. nov. (dark zone of Kabirano-ana cave) (all photos by F. Ballarin).

Figure 16. 

Distribution of Nesticella and Howaia species in mainland Japan and Ryukyu Archipelago A distribution of N. brevipes and N. terrestris in mainland Japan and neighboring countries B distribution of Nesticella and Howaia species endemic to the Ryukyu Archipelago C distribution of H. mogera in mainland Japan and neighboring countries D distribution of H. mogera in the Ryukyu Archipelago and neighboring countries. Colored squares refer to the type localities of the species, colored dots indicate the locations of specimens whose morphology has been checked during this study, dashed areas refer to the generally known distribution of the species, question marks refer to unclear distributions (see “remarks on misidentifications” of N. brevipes and N. terrestris).

Figure 17. 

Size comparison between Nesticella brevipes and N. terrestris A visual comparison of adult females of Nesticella brevipes (left) and N. terrestris (right) B Scatterplot of the Tibia I / carapace lengths ratio in females of N. brevipes (blue circle) and N. terrestris (orange circles). Measurements are reported in millimeters. Scale bar: 1 mm (A).