Nyctimus bistriatus Thorell, 1877

Benjamin, Suresh P., Dhiya’ulhaq, Naufal Urfi, Deeleman-Reinhold, Christa, Buchori, Damayanti, Hidayat, Purnama, Scheu, Stefan & Drescher, Jochen, 2025, Taxonomic notes on the crab-spider genera Nyctimus Thorell, 1877 and Zametopina Simon, 1909 (Araneae, Thomisidae) with descriptions of six new species from Southeast Asia, ZooKeys 1255, pp. 95-125 : 95-125

Nyctimus bistriatus Thorell, 1877

Figs 1 , 2 , 3

Nyctimus bistriatus Thorell, 1877: 499; Lehtinen 2016: 166 (as Nyctimus binotatus, lapsus).

Zametopias speculator Thorell, 1892: 123.

Type material.

Holotype. Indonesia – Sulawesi, Southeast Sulawesi Province • ♂; Kendari ; 1874; O. Beccarii leg.; holotype of Nyctimus bistriatus Thorell, 1877 ; MCSN. Examined.

Other material examined.

Brunei – Tutong District • 1 ♂; Bukit Sulang ; 1982; N. Stork leg.; canopy fogging in primary forest; RMNH RMNH.ARA.17873 . Indonesia – Sumatra, Jambi Province • 1 ♀; Sarolangun, Bukit Duabelas National Park ; 01°58'55.2"S, 102°45'02.6"E; elev. 73 m; 7 Oct. 2013; J. Drescher leg.; canopy fogging in rainforest; GOET 2013_BF 2.1_AraThom 051 N_001 (to be transferred to MZB) . Malaysia – Sabah State • 1 ♂; Kinabalu National Park, Poring Hot Springs ; 05°59'N, 116°42'E; elev. 600–700 m; 27 Feb. 1996; A. Floren leg.; canopy fogging on Aporosa lagenocarpa tree, in primary forest; RMNH RMNH.ARA.17874 . • 1 ♀; Kinabalu National Park, Poring Hot Springs ; 05°59'N, 116°42'E; elev. 600–700 m; 28 Mar. 1998; A. Floren leg.; canopy fogging on Barringtonia tree, in primary forest; RMNH RMNH.ARA.17875 . • 1 ♂; Kinabalu National Park, Poring Hot Springs ; 05°59'N, 116°42'E; elev. 600–700 m; 28 Mar. 1998; A. Floren leg.; canopy fogging on Dacryodes laxa tree, in primary forest; RMNH RMNH.ARA.17876 .

Diagnosis.

Males can be easily distinguished from all other congeners by the longer embolus, more than length of cymbium (in all congeners, the embolus is at most half the length of cymbium; Fig. 3 A, B ) and the denticulate RTA. Females can be easily distinguished by the single CO; CD arched, resembling a rams’ horn, more than twice the length of spermathecae (in all congeners, the CO is paired, and the CD are not longer than spermathecae; Figs 2 C, D , 3 C, D ).

Description.

Male ( RMNH.ARA.17873 ; Figs 1 A , 3 A, B ). Total length 2.85. Prosoma length 1.42; width 1.26. Opisthosoma length 1.43; width 1.17. Diameter of eyes: AME 0.09; ALE 0.15; PLE 0.14 PME 0.07. Interdistances between eyes: AME – AME 0.50; AME – ALE 0.10; ALE – ALE 0.86; PME – PME 0.70; PME – PLE 0.20; ALE – PLE 0.18; AME – PME 0.13; PLE – PLE 1.09. Leg measurements: leg I 3.3 (1.0, 0.5, 1.0, 0.8, 0.5). Prosoma cuboid, almost as long as wide; dorsally blackish brown, surface granulated; laterally with two rows of long, curved macrosetae originating on small tubercles. All eyes are very far apart, especially between the median eyes. Chelicerae, labium and sternum blackish brown; sternum with small dents. Legs dark brown except femora III and IV, which are yellow; femora and tibiae I – IV with two long spines; patellae I – IV with one distal long spine. Opisthosoma dorsally greyish black with many long setae; five large sigillae present, arranged in a triangular formation; venter greyish black.

Palp (Fig. 3 A, B ): cymbium oval. Embolus long, whip-like, looping over the retrolateral side of bulb, half of its length covered by the cymbium. Tegular hood small, located close to the base of bulb. RTA large, roughly trapezoid, laterally protruding, distal half with denticles on all sides. VTA long, digitiform; apically flexed with tip ventrally curved.

Female ( RMNH.ARA.17875 ; Figs 1 B , 3 C, D ). Total length 3.32. Prosoma length 1.15; width 1.30. Opisthosoma length 2.17; width 1.95. Diameter of eyes: AME 0.08; ALE 0.13; PLE 0.16; PME 0.06. Interdistances between eyes: AME – AME 0.56; AME – ALE 0.10; ALE – ALE 0.86; PME – PME 0.64; PME – PLE 0.21; ALE – PLE 0.18; AME – PME 0.16; PLE – PLE 1.09. Leg measurements: leg I 5.3 (1.6, 0.6, 1.3, 1.0, 0.8). Habitus as in male, except opisthosoma dorsally lighter than male and the presence of white spots as shown in Fig. 1 B .

Epigynum (Figs 2 C, D , 3 C, D ): exterior plate roughly pentagonal. Atrium inconspicuous. CO oval, single, large, CD long; divided into a very wide, ramshorn-shaped initial part and a narrow, C-shaped later part. Spermatheca globular, approximately as wide as CO; anteriorly with a small bump; posteriorly extended.

Distribution.

Brunei, Malaysia (Borneo: Sabah), Indonesia ( Sumatra: Jambi; Sulawesi: Southeast Sulawesi) (Fig. 19 ).

Figures

Figure 1. Nyctimus bistriatus Thorell, 1877 from Borneo; habitus, dorsal view. A. Male (RMNH. ARA. 17873); B. Female (RMNH. ARA. 17875). Scale bars: 0.5 mm.

Figure 2. Nyctimus bistriatus Thorell, 1877 female from Sumatra (2013 BF 2.1 AraThom 051 N 001). A. Habitus, dorsal view; B. Prosoma, frontal view; C. Epigynum, ventral view; D. Epigynum, dorsal view, cleared. Scale bars: 1 mm (A); 0.5 mm (B); 0.2 mm (C, D).

Figure 3. Nyctimus bistriatus Thorell, 1877 from Borneo. A. Male (RMNH. ARA. 17873), left palp, ventral view; B. ibid., retrolateral view; C. Female (RMNH. ARA. 17875), epigynum; C. ibid., ventral view; D. ibid., dorsal view. Abbreviations: CD = copulatory duct; CO = copulatory opening; E = embolus; FD = fertilization duct; RTA = retrolateral tibial apophysis; S = spermatheca; TH = tegular hood; VTA = ventral tibial apophysis. Scale bars: 0.2 mm.

Figure 19. Distribution of all described Nyctimus and Zametopina (Araneae: Thomisidae) species. Grey circles surrounding white dots indicate species collected from the same or very closely located sampling points in Brunei, Sabah (Malaysia), and Jambi (Indonesia).