Pygmarrhopalites sericus ( Gisin, 1947 )

Vargovitsh, Robert S., 2025, Antennal troglomorphy in Arrhopalitidae (Collembola: Symphypleona) with the description of two new cave Pygmarrhopalites Vargovitsh, 2009 species from the Arabika Massif in the Caucasus, Zootaxa 5673 (4), pp. 523-556 : 545

Pygmarrhopalites sericus ( Gisin, 1947) : first record for the Caucasian fauna

Material examined a) 3 females on slides (C-1085-1, C-1085-2, C-1085-3): W Caucasus, Abkhazia, Gagra Mt. R., Arabika Massif , 1,805 m a.s.l., Trechus Grotto, 5–10 m from entrance, on liquid surface of Barber traps, 9.vii.2016 – 12.ix.2017 , A.G. Koval and R. S. Vargovitsh leg.; numerous specimens from same locality, same collectors, same method, preserved in alcohol (9.vii.2016, 12.ix.2017, 14.ix.2018) .

b) 2 females on slides (C-1086a-1, C-1086a-2): W Caucasus, Abkhazia, Gagra Mt. R., Arabika Massif, 1,980 m a.s.l., Treugolnaya Cave , 10–15 m from entrance, on liquid surface of Barber traps, 12.ix.2017, R. S. Vargovitsh and A.G. Koval leg.; numerous specimens from same locality preserved in alcohol .

c) 1 female on slide (C-1084a-1): W Caucasus, Abkhazia, Gagra Mt. R ., Arabika Massif, 2,223 m a.s.l., Zh-13 Cave , - 5 m, on liquid surface of Barber trap, 11.ix.2017, A.G. Koval and R. S. Vargovitsh leg.

Taxonomic remarks. The examined specimens generally correspond to the original descriptions of P. sericus ( Gisin 1947, 1960): body length ~ 0.7 mm; body and eyes with greyish pigmentation; head dorsum bearing ordinary setae, with 2 + 2 posterior setae thicker than anterior ones; Ant IV divided into 5 subsegments, basal subsegment ~1.3× as long as apical; all claws with inner tooth; Abd VI with 13 broadened setae; appendices anales palmated ( principalis type); dens chaetotaxy as in P. principalis , including 2 outer and 3 inner distinctly spine-like setae.

Additional characters observed in the Caucasian material include: body length 0.7–0.8 mm; antenna 1.5–1.6× head length; basal subsegment of Ant IV slightly shorter than Ant III; head dorsum with 4 unpaired axial setae and with lateral seta D2 of the most posterior D -row thicker than others; seta m1 of Th II thick (much thicker than all other setae on great abdomen) and relatively long; circumanal setae longer than posterior abdominal setae; all claws with tunica; empodium I with corner tooth, empodia II – III without; empodial filaments of legs I– II distinctly overtopping corresponding claw, and of leg III reaching or overtopping claw tip; tenaculum with 2 setae; manubrium with 6 + 6 setae; mucro with narrowed, almost pointed tip. The thickness of head dorsum setae varies among cave populations: thin in specimens from Trechus Grotto, and slightly spine-like—especially seta D2—in those from Treugolnaya and Zh-13 caves.

It should be emphasized that Gisin’s (1947, 1960) original descriptions, as well as some subsequent descriptions of the species, are brief and omit several key characteristics. Consequently, comparison with the type material is necessary for accurate identification of the Caucasian populations.

Distribution. Pygmarrhopalites sericus is a Western Palaearctic species, widely distributed in Europe; it has also been recorded in Morocco ( Thibaud & Massoud 1980) and the Middle Ural region of Russia ( Kuznetsova 2009). It has not been previously reported from the Caucasus.