Porrhomma pallidum Jackson, 1913

Růžička, Vlastimil, 2018, A review of the spider genus Porrhomma (Araneae, Linyphiidae), Zootaxa 4481 (1), pp. 1-75 : 50-52

Porrhomma pallidum Jackson, 1913

Figs. 45A–F .

Porrhomma pallidum — Jackson (1913): p. 38, Pl. II, Figs. 18 , 32 (descr. ♂ ♀).

P. pallidum affinis — Miller & Kratochvíl (1940): p. 189, Figs. 12.3, 13.1–2 (descr. ♂ ♀); new synonymy.

Material examined. CZECHIA: Krkonoše Mts. National Park, Harrachov, Mrtvý Vrch Hill , 1982–1989, 4 Ƌ 5 ♀ , leg. J. Vaněk. Tisá, Tiské Stěny Rock Walls Reserve, 12 May 1991, 2 Ƌ 3 ♀, leg. F. Růžička. Nižbor, Vůznice Reserve, 14 Jun –2 Jul 1993, 1 Ƌ 1 ♀ , leg. F. Pojer. Verneřice-Loučky, Bobří Soutěska Gorge Reserve, 1 Jun 1986 – 16 May 1987, 1 ♀, 19 Oct 1999, 1 ♂ 1 ♀; Teplice nad Metují, Adršpašsko-Teplické Skály Rocks Reserve , 24 Oct 1987, 1 ♂ 2 ♀ ; Šumava Mts., Srní, Vydra River Valley , 23 Jul 1992, 1 ♀ ; Šumava Mts., Stachy-Popelná, Obří Zámek Hill , 6 Oct 1985 – 4 Oct 1986, 1 ♂ ; Lnáře-Tchořovice , 30 May 1975, 1 ♀ ; Rokycany-Svojkovice, Žďár Hill, 5 May 1998, 1 ♀; leg. V. Růžička. Teplice nad Metují, Adršpašsko-Teplické Skály Rocks , 2006–2009, 9 ♂ 10 ♀, leg. R. Mlejnek ( IECA) . SLOVAKIA: Námestovo , 23 Jun 1971, 1 Ƌ, leg. J. Svatoň ( WSM) . UNITED KINGDOM: Scotland, Tentsmuir Coast, 21 Jun 1966, 2 ♀ ( AMNH) .

Diagnosis. Females of P. pallidum are similar to those of P. altaica , P. egeria , P. campbelli and P. terrestre in having the simplest vulva (the spermathecae are formed immediately behind the side loop) but can be distinguished by appendices oriented towards the abdominal wall ( Figs. 45C–F ). On the other hand, males of P. pallidum are similar to those of P. borgesi , P. cambridgei , P. convexum , P. errans , P. nekolai , P. oblitum , P. pygmaeum and P. rosenhaueri in having embolus of middle length with a narrow velum and ARP of the form of a bird head ( Fig. 45B ). Males of P. pallidum can be distinguished by the following combination of characters: yellow-brown carapace, 0.60–0.69 mm wide, eyes normal, Fe I–II with dorsal spines, Mt without spines.

Description. ♀ (from Srní, Czechia, 23 Jul 1992). Carapace yellow-brown, 0.63 mm wide, PME–PME = 1.3 ( Fig. 45A ). Abdomen pale. Fe I–II with one dorsal spine, Fe I with one prolateral spine. Ti I with one prolateral spine, Ti I–II with one retrolateral spine. Tm Mt I = 0.35, Mt I/CW = 0.88.

Spermathecae start at the midway of the ascending part of the copulatory ducts. Main sacks oriented towards abdomen. Appendices oriented towards the abdominal wall ( Figs. 45C–F ).

Ƌ (from Nižbor, Czechia, 14 Jun–2 Jul 1993). Embolus of middle length with a narrow velum. ARP has the form of a bird head ( Fig. 45B ).

Variation. Ƌ ♀. Carapace 0.60–0.69 mm wide. Tm Mt I = 0.30–0.39, Mt I/CW = 0.79–0.92 (n = 37).

Comments. The subspecies P. p. affinis was described by Miller & Kratochvíl (1940) according to one male and several females collected in High Tatras, Slovakia. The type material is not available (Růžička et al. 2008). I found all details in the structure of copulatory organs to be fully within the frame of the natural variability of P. pallidum .

Ecology. The species occurs under stones in scree slopes, scree forests, in cold habitats such as rock gorges, spruce forests, peat bogs.

Note. All records of P. pallidum in Altai Mountains are misidentification and actually refer to P. altaica new species (see above).

Global distribution. Eurasia after Helsdingen (2017), Mikhailov (2013) and Tanasevitch (2009). See Fig. 46 .

Figures

FIGURE 18. Global distribution of Porrhomma cavernicola.

FIGURE 32. Global distribution of Porrhomma microphthalmum.

FIGURE 45. A–F, Porrhomma pallidum from Srní, Czechia; except B, Nižbor, Czechia. A, ♀ carapace, frontal view. B, embolic section. C, epigynum. D–F, vulva, ventral, caudal and dorsal. Scale bars, 0.1 mm.

FIGURE 46. Global distibution of Porrhomma pallidum.