Chthonius horridus Beier 1934
Creators: name: Gardini, Giulio
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Pseudoscorpiones
Chthoniidae
Chthonius
Chthonius horridus

description: Chthonius horridus Beier, 1934 (n. stat.)
(Figs 188–211, 413)
Chthonius (C.) cephalotes ssp. horridus Beier, 1934: 54, fig. 2.
Chthonius (C.) doderoi horridus: Heurtault-Rossi 1968: 921.
Chthonius cephalotes: Boldori 1932: 127.
Type locality: Italy, Piedmont, Biella Province, Santuario di Oropa (45°37’42”N, 7°58’44”E).
Distribution. Italy (from Brescia Pre-Alps to Pennine Alps).
Diagnosis (♂ ♀). An anophthalmic or microphthalmic hypogean Chthonius that differs from other species of the ischnocheles group in the following combination of characters: anterior margin of carapace with 1 preocular microseta on each side; posterior margin of carapace with 2 macrosetae and 1 (rarely 2) lateral microsetae on each side; chelicerae with 2 (rarely 3) lateral microsetae; chelal fingers with long, sharp, slightly reclined and widely spaced teeth; both fixed and movable chelal fingers at level of est-ist and st-t with 3–4 teeth occupying 0.1 mm, distance between successive apices 0.023 –0.046.
Type material examined. ITALY — Piedmont: 1 ♀ (holotype) “Oropa, A. Dodero leg., 1925” “ Chthonius cephalotes ssp. horridus n. ssp., det. Beier, Type! ♀ ” (MSNG); 1 ♂ 2 ♀ (paratypes), “Oropa (Novara), estate 1924, A. Dodero ” “ Chthonius cephalotes ssp. horridus nov., det. Beier, Paratypen ” (MSNG).
Other material examined. ITALY — Lombardy: Bergamo Prov. — 1 ♂, Abbazia-Albino, Miniera Superiore Vena Coserino, 28.XI.1981, G. Comotti leg.; 2 ♂ 3 ♀, Costa d’Imagna, Grotta sotto tornante, 1200 m a.s.l., 26.IX.1987, G. Comotti & A. Baldan leg.; 1 ♂ 1 ♀, Costa d’Imagna, Grotta di Fopa Taria 3540 Lo /BG, 25.IX.1988, G. Comotti & A. Baldan leg.; 4 ♂ 3 ♀, Dossena, mine at S slope of Monte Vaccareggio, 1300 m a.s.l., 29.XI.2014, M. Grottolo & D. Pedersoli leg.; 4 ♀, id., 18. VI.2016, M. Grottolo leg.; 1 ♂, Gorno, mine of Gorno, 26.IV.2013, L. Bodei leg.; 2 ♀, Monasterolo, Stampa dei Pagà 1370 Lo /BG, 6. VI.2015, M. Grottolo leg.; 1 ♂, Olmo al Brembo, Büs del Magher 1057 Lo /BG, 700 m a.s.l., 31. V.1994, E. Piva leg.; 2 ♀, Oltre il Colle, 20.IX.1987, M. Grottolo leg., beech wood; 8 ♀, id., 1200 m a.s.l., 8.X.1988, M. Grottolo leg., beech wood; 1 ♀, Oltre il Colle, mine of Monte Arera, 1950 m a.s.l., 20. VI.2015, D. Pedersoli leg.; 1 ♂, Oltre il Colle, Zambla, Monte Arera, mine at 1500 m a.s.l., 6. V.2017, M. Grottolo leg.; 3 ♀, id., mine at 1530 m a.s.l., 6. V.2017, M. Grottolo leg.; 2 ♂ 1 ♀, Rota d’Imagna, Tomba dei Polacchi 1003 Lo /BG, 20.I.1981, R. Sciaky & S. Zoia leg.; 1 ♂, id., 22.VII.1986, M. Grottolo leg.; 2 ♀, id., 15.IV.1989, M. Valle leg., entrance; 2 ♀, id., 2. VIII.1989, E. Piva leg.; 1 ♂, Valleve, Bocchetta di San Simone, 2000 m a.s.l., 25.IX.1999, L. Bodei leg. Lombardy: Brescia Prov. — 1 ♂, Lavenone, road to Presegno, 29.XI.1998, M. Grottolo leg.; 1 ♀, Magasa, Cuel in località Cordéter 436 Lo /BS, 18. V.1975, D. Vailati leg.; 1 ♂, Provaglio Val Sabbia, Monte Colmo, mine Büs de la Vena art. Lo /BS, 26.II.2011, L. Bodei leg. Lombardy: Como Prov. — 1 ♀, Sormano, Pian del Tivano, Grotta Falsa Squarada 2619 Lo /CO, 1118 m a.s.l., 2.IV.2014, L. Aimar leg.; 1 ♀, Sormano, Pozzo presso la Capanna Stoppani, 1000 m a.s.l., 2.IV.2004, R. Monguzzi leg. Lombardy: Lecco Prov. — 1 ♀, Cassina Valsassina, Culmine di San Pietro, Grotta dell’Edera n.c. Lo /LC, XII.1987, D. Baratelli leg.; 1 ♂, Mandello del Lario, Grotta Ferrera 1502 Lo /LC, 590 m a.s.l., 18.XI.2017, V. Balestra & E. Lana leg. Piedmont: Biella Prov. — 1 ♂ 2 ♀, Sagliano Micca, Valle Cervo, mine of Passobreve (B) art. Pi /BI, 624 m a.s.l., 14.IV.2001, T. Pascutto, S. Bugalla & F. Aimone leg.; 1 ♀, id., mine of Passobreve (A) art. Pi /BI, 6.XII.2019, E. Lana & D. Trombin leg.; 1 ♀, id., Miniera Vittorio Amedeo 2, 30.I.2020, D. Trombin leg.; 1 ♂, id., 2. VI.2020, D. Trombin leg.; 1 ♀, Sostegno, Grotta di Bercovei 2503 Pi /BI, 450 m a.s.l., 3.IX.1994, T. Pascutto leg.; 1 ♀, id., 31.III.1996, T. Pascutto leg.; 1 ♂, Trivero, Tana del Diavolo 2797 Pi /BI, 1392 m a.s.l., 10. VIII.2011, E. Lana leg.; 1 ♂, Valdilana, Bocchetta di Margosio, 1400 m a.s.l., 3. VI.2006, L. Bodei leg. Piedmont: Novara Prov. — 1 ♀, Grignasco, Cavità del Molin dal Togn 2774 Pi /NO, 410 m a.s.l., 10.XII.2014, E. Lana & R. Sella leg. Piedmont: Torino Prov. — 1 ♀, Settimo Vittone, Frattura di Panvolio o dello Pselaphogenius 1759 Pi /TO, 815 m a.s.l., 20.X.2012, E. Lana leg.
Description of adults (♂ ♀) (Females of Bercovei cave excluded: see below). Integument slightly pigmented, pale brown; hispid granulation on lateral surfaces of carapace, on cheliceral palm, on the base of fixed chelal finger, on paraxial surface and on dorso–distal surface of chelal hand. Carapace (Fig. 190) 0.90–1.05 times longer than broad, trapezoidal, constricted posteriorly; anterior margin strongly denticulate between the median macrosetae, without a prominent epistome in males, rarely with a small epistome in females (Figs 188–189); ocular area as in fig. 190, anterior eyes mainly absent, rarely with flat lens (diameter 0.025 mm: ♂ from Ferrera cave) or reduced to a cuticular pale area, posterior eyes absent; chaetotaxy m 4m:6:4:2:m 2m (22), rarely posterior row m 2mm; length of anteromedian macrosetae 0.16–0.22 mm. Chaetotaxy of tergites 4:4:4:4:6:6:6:6:1T2T1:4:1T2T1:0. Chaetotaxy of sternites II–X: 9–11:(3)9–10(3):(2)7(2):7–9:6–8:6:6:6:2T1T2; genital opening of males flanked by 6–9 setae on each side. Chelicerae (Fig. 191) 2.35–2.65 times as long as broad, palm with 6 setae and 2 (rarely 3) lateral microsetae; fixed finger with 9–13 teeth, of which the distal last but one larger; movable finger with an isolated subapical tooth (di) at level with the spinneret, a large distal tooth and 8–11 teeth proximally reduced in size; gs ratio 0.52–0.60; spinneret weakly raised in males, more prominent in females; rallum with 11 blades; serrula interior with 14–16, exterior with 17–19 blades. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3–4 + 3 marginal microsetae, II 4–5, III 5, IV 6; coxa II with 9–20 coxal spines, coxa III with 4–8 coxal spines; intercoxal tubercle bisetose (1m in ♀ from Frattura di Panvolio). Pedipalp: femur 6.1–7.5 times as long as broad, standard femoral chaetotaxy 3:5:3:5:1; chela (Figs 195, 199) 5.95–7.25 (♂) or 5.65–5.95 (♀) times as long as deep; hand of chela 2.0–2.4 (♂) or 1.9–2.15 (♀) times as long as deep, with long oval to parallel outline in dorsal view (Figs 193–194); fixed chelal finger with 35–54 (♂) or 29–47 (♀) teeth: (3)4 small, triangular distal teeth, followed by 21–39 large, sharp, slightly reclined and widely spaced teeth and 5–17 teeth increasingly reduced and closer together towards finger base (Figs 196–198, 200–202); all teeth with dental canal; base of fixed chelal finger with 5–8 microtubercles; fixed finger at level of est-it mainly with 3–4 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.025 –0.041 (♂) or 0.030 –0.046 (♀) mm; tip of fixed chelal finger with apical sensilla af 1- 2, distal paraxial seta gradually curved and thin; movable chelal finger with 33–53 (♂) or 29–44 (♀) teeth, these large, sharp, slightly reclined and widely spaced in the distal half of the finger, apically broadly rounded and increasingly reduced towards finger base in the proximal half of the finger, reaching back nearby b (Figs 196–198, 200–202); movable finger at level of st-t with 3–4 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.023 –0.043 (♂) or 0.025 –0.041 (♀) mm; coupled sensilla pc mainly just distad of sb, rarely (♂ from Ferrera cave) nearer to st than to sb, on a weak tubercle; tip of movable chelal finger with apical sensilla am 1- 2; trichobothria as in figs 195, 199; ratio sb -st/sb -b = 1.8–2.1; ratio of movable finger/hand of chela 1.7–2.15 (♂) or 1.7–1.9 (♀); ratio of pedipalpal femur/movable finger 1.0–1.1 (♂ ♀); ratio of pedipalpal femur/carapace 1.7–1.85 (♂ ♀).
Measurements (in mm). Body length 1.9–2.5 (♂) or 1.8–2.8 (♀). Carapace 0.51–0.69 × 0.53–0.70 (0.50–0.66 anteriorly) (♂) or 0.54–0.74 × 0.57–0.78 (0.55–0.76 anteriorly) (♀). Chelicerae 0.54–0.74 × 0.21–0.28 (♂) or 0.56–0.81 × 0.225–0.33 (♀); movable finger length 0.275–0.37 (♂) or 0.29–0.43 (♀). Pedipalp: femur 0.90–1.22 × 0.135–0.17 (♂) or 0.91–1.31 × 0.145–0.19 (♀); chela 1.29–1.79 × 0.19–0.28 (♂) or 1.31–1.95 × 0.22–0.33 (♀); hand length 0.43–0.66 (♂) or 0.44–0.71 (♀); movable finger length 0.86–1.13 (♂) or 0.87–1.23 (♀).
Description of females from Bercovei cave. Carapace with a small epistome; anterior eyes absent or reduced to a cuticular pale area, posterior eyes absent; length of anteromedian macrosetae 0.12–0.13 mm. Chaetotaxy of sternites II–X: 10:(2)8(3):(2)7(2):9:7:6:6:6:2T1T2. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 3 marginal microsetae, II 4, III 5, IV 6; coxa II with 7–8 coxal spines, coxa III with 4–5 coxal spines. Pedipalp: femur 5.5–5.6 times as long as broad; chela 5.45–5.8 times as long as deep; hand of chela 1.75–1.95 times as long as deep, fixed chelal finger with 29–31 teeth; fixed finger at level of est-it with 3 teeth occupying 0.1 mm, distance between successive apices 0.030 –0.034 mm; movable chelal finger with 26–29 teeth; movable finger at level of st-t with 4 teeth occupying 0.1 mm, distance between successive apices 0.025 –0.027 mm; coupled sensilla pc just distad of sb; ratio of movable finger/hand of chela 1.95–2.1; ratio of pedipalpal femur/movable finger 0.95–1.0; ratio of pedipalpal femur/carapace 1.35–1.75.
Measurements (in mm). Body length 1.7. Carapace 0.46–0.53 × 0.53–0.54 (0.50 anteriorly). Chelicerae 0.53– 0.54 × 0.22–0.235; movable finger length 0.28–0.29. Pedipalp: femur 0.72–0.73 × 0.13; chela 1.09–1.10 × 0.19– 0.20; hand length 0.35–0.375; movable finger length 0.73–0.745.
Remarks. Chthonius cephalotes was described (as Blothrus cephalotes) by Simon (1875) based on a female collected within Grotte de Baux, near Saint-Martin-de-Craux (Bouches-du-Rhône). Beier (1930) described C. cephalotes doderoi on the basis of a male and a female collected by A. Dodero in the Grotte de Méailles (Alpes-de- Haut-Provence) and subsequently (Beier 1934), he described C. cephalotes horridus from a male and three females that were also collected by A. Dodero near the Sanctuary of Oropa (Piedmont). The latter differs from both the nominotypical subspecies and from the ssp. doderoi in having numerous, long and sharp chelal teeth (Beier 1934).
Heurtault-Rossi (1968) redescribed the female holotype of Chthonius cephalotes and underlined its many differences with doderoi and horridus. She removed both subspecies from C. cephalotes and considered both as subspecies of C. doderoi. The original description of C. doderoi that was published by Beier (1930) is insufficient and lacks figures. An additional problem is that the types at the MSNG are missing and were presumably lost during the flood of September 28, 1992.
Thanks to the courtesy of Dr Mark Judson (MNHN), I had the opportunity to examine (February 28, 2020) his preliminary descriptions and drawings of two specimens (♂ ♀) from the caves Grotte de la Lare (St Benoït) and Grotte du Chat (Daluis) near the type locality of Chthonius doderoi. They are almost certainly referable to this species. These specimens differ from the Italian ones primarily in the characters listed above, most importantly in the shape of the teeth in the distal half of the movable chelal fingers: very reclined and low in specimens from France that are attributed to C. doderoi, but almost erect, tall and pointed in specimens from Italy. Chthonius horridus Beier, 1934 is therefore considered a distinct species from C. doderoi Beier, 1930 (n. stat.).
Among the species of the Chthonius ischnocheles group, C. horridus is morphologically similar to the subterranean C. doderoi from south-eastern France, with which it shares the presence of a preocular microseta on each side, the posterior margin of carapace with 1 microseta on each side (rarely 2 in C. horridus), chelicerae with 2 lateral microsetae and body measurements. Chthonius horridus differs from C. doderoi in the shape of the movable chelal teeth, as specified above.
Note that two females of Bercovei cave (Sostegno, Biella) are described separately due to their small size, but still referred to Chthonius horridus.
The Passobreve mine (Sagliano Micca, Biella) from which the illustrated specimens originate is located about 4.5 kilometers in a straight line from the Santuary of Oropa, the type locality of Chthonius horridus. Variability of chelal dentition in C. horridus is represented in figs 203–211.
description: Published as part of Gardini, Giulio, 2021, The Italian species of the Chthonius ischnocheles group (Arachnida, Pseudoscorpiones, Chthoniidae), with reference to neighbouring countries, pp. 1-131 in Zootaxa 4987 (1) on pages 63-68, DOI: 10.11646/zootaxa.4987.1.1, http://zenodo.org/record/4979653