Chthonius

Gardini, Giulio, 2013, A revision of the species of the pseudoscorpion subgenus Chthonius (Ephippiochthonius) (Arachnida, Pseudoscorpiones, Chthoniidae) from Italy and neighbouring areas, Zootaxa 3655 (1), pp. 1-151 : 103-108

Chthonius (E.) siculus Beier, 1961

( Figs 196–204 , 283 )

Chthonius (Ephippiochthonius) siculus Beier 1961: 90 , fig. 1.

Chthonius (E.) tetrachelatus (not Preyssler, 1790): Lazzeroni 1969a: 324 (misidentification, in part).

Chthonius (E.) gibbus (not Beier, 1953): Mahnert 1975: 186, figs 1a, 1c (misidentification).; Callaini 1979a: 134, figs IIa, b (misidentification); Callaini 1983b: 403 (misidentification); Callaini 1989: 138 (misidentification); Gardini 1995a: 3 (misidentification); Gardini 1995b: 45 (misidentification); Gardini et al. 1997: 221 (misidentification, in part); Gardini 2008b: 631 (misidentification).

Not Chthonius (E.) siculus : Mahnert 1976: 309 (misidentification, see C. concii ); Mahnert 1980: 223 (misidentification); Gardini 1980: 103 (misidentification, see C. concii ); Zaragoza 1985: 154 (misidentification).

Chthonius (Ephippiochthonius) cfr. gibbus: Callaini 1986: 345 , fig. Ic (misidentification).

Chthonius (E.) siculus : Gardini 2007: 384; Gardini 2008a: 8, figs 11–16.

Type locality: Italy, Sicily, Siracusa Prov., Pachino, Grotta Calafarina 3510 Si/SR (36°43ʹ19ʺN 15°07ʹ0 2ʺE).

Distribution. Central-southern Italy, Sicily, Sardinia.

Diagnosis (Ƥ). An eyed epigean Chthonius (Ephippiochthonius) that differs from other species of the C. tetrachelatus group in the following combination of characters: movable cheliceral finger without isolated tooth (di) and with spinneret in both sexes; posterior margin of carapace mostly with 2 macrosetae (rarely with 1 on each side); hand of chela depressed at level of trichobothria ib-isb and with hump distad of ib-isb; fixed and movable chelal fingers respectively with 12–20 and 6–9 triangular teeth; rounded teeth reduced in size proximally, but still distinguishable as far as base of fingers; fixed chelal finger at level of est-it with 4–6 teeth occupying 0.1 mm (distance between successive apices 0.019–0.022 mm); length of chela 0.48–0.72 (3), 0.53–0.81 (Ƥ); length of movable chelal finger 0.28–0.41 (3), 0.30–0.45 (Ƥ); chela 4.5–6.0 (3), 4.0–5.2 (Ƥ) times as long as deep; ratio of pedipalpal femur/carapace 1.1–1.3 (3Ƥ).

Type material examined. ITALY— Sicily: Siracusa Prov.— 1 3 1 Ƥ (syntypes) “ Typen, Chthonius (E.) siculus n. sp. ” M. Beier det., Pachino, Grotta Calafarina, 11.XII.1960, leg.? (MSNV).

Other material examined. ITALY — Latium: Latina Prov. — 1 Ƥ, Cisterna, 28.X.2002, G. Nardi leg. (CNBFVR); 1 3, San Felice Circeo, Peretto, 190 m a.s.l., 3–17.V.2005, G. Forcina & A. Noal leg.; 1 Ƥ, id., 8– 19.VII.2005 (CNBFVR); 1 Ƥ, Ventotene, 12.IV.2008, L. Galli leg., Mediterranean scrub under Genista and Ferula . Latium: Rome Prov.— 1 3, Tolfa, near Rota, 23.IV.1972, A. Vigna leg. Campania: Naples Prov.— 1 3 1 Ƥ 2T 1D, Torre del Greco, Camaldoli della Torre, 29.IX.1982, G. Gardini & S. Zoia leg., Quercus ilex wood. Apulia: Bari Prov.— 1 Ƥ, Gravina di Puglia, 6.IV.1985, S. Vit leg. (MHNG). Apulia: Foggia Prov.— 1 Ƥ, Apricena, 6 km NNE Apricena, 290 m a.s.l., 4.V.2002, S. Zoia & F. Polese leg. Apulia: Taranto Prov.— 1 3 ( C. tetrachelatus, G. Lazzeroni det.), Mottola, 24.IX.1967, C. Baroni Urbani leg. (MSNV) (together with 10 3 1 Ƥ of C. tetrachelatus ). Sicily: Agrigento Prov.— 2 3 2 Ƥ 5T 2D, Santo Stefano di Quisquina, 9.VII.1996, B. Massa leg., soil Pinus halepensis ; 2 Ƥ 4T, id., 9.VII.1996, soil Cedrus atlantica ; 5 3 5 Ƥ 7T 1D, id., 13.XI.1996, soil Pinus and Cedrus ; 5 3 4 Ƥ 6T, id., 24.II.1997; 7 3 15 Ƥ 4T 2D, id., 7.V.1997. Sicily: Caltanissetta Prov.— 3T (M. Beier det.), Niscemi, Monte Ursitto, 24.II.1962, La Greca & Sichel leg. (MSNV). Sicily: Catania Prov.— 2 3 3 Ƥ 5T 2D, Acitrezza, Isole dei Ciclopi, Isola Lachea, 28.IV.2000, S. Zoia & F. Polese leg., under Opuntia ; 1 Ƥ, Fiumefreddo, 31.VIII–21.IX.1994, F. Di Franco leg., Rubus scrub; 1 3, id., 14.XI–13.XII.1994; 2 Ƥ 2T, id., 4–25.II.1995, F. Di Franco leg.; 1 Ƥ, id., 20.III–8.IV.1995; 2 3 3 Ƥ 1T, id., 8–29.IV.1995, F. Di Franco leg., Rubus scrub; 1 3 2 Ƥ, id., 29.IV–13.V.1995, F. Di Franco leg., under Arundo ; 1 3 1 Ƥ 1T, Linguaglossa, 8.III.2001, B. Massa leg., Fagus sylvatica and Quercus pubescens wood on volcanic soil. Sicily: Messina Prov.— 1 3 1 Ƥ ( C. gibbus, G. Gardini det. 1994), Caronia, Case Crocitti, 750 m a.s.l., IX.1987, G. Sabella leg., Quercus pubescens wood; 1 3 ( C. gibbus, G. Gardini det. 1994), id., VIII.1988; 1 Ƥ ( C. gibbus, G. Gardini det. 1994), Caronia, Contrada Moglia, 1400 m a.s.l., X.1987, G. Sabella leg., Fagus sylvatica wood; 3 3 2 Ƥ 2T ( C. gibbus, G. Gardini det. 1994), Cesarò, Monte Soro, 16.VI.81, G. Gardini leg., Quercus cerris wood; 1 3 1T ( C. gibbus, G. Gardini det. 1994), id., 16.VI.1981, G. Gardini leg., Fagus sylvatica wood; 1 3 1 Ƥ ( C. siculus, M. Beier det.), Isola Lipari, Quattropani, 22.II.1966, Alicata leg. (MBAC); 1 3, Isola di Salina, 7.IV.1990, R. Argano leg.; 2 3 4 Ƥ ( C. gibbus, G. Gardini det. 1994), Montalbano Elicona, Bosco Malabotta, 24.V.1981, P. Brandmayr leg., Quercus cerris wood; 2 3 ( C. gibbus, G. Gardini det. 1994), id., 24.V.1981, P. Brandmayr leg., Fagus sylvatica wood; 11 3 3 Ƥ ( C. gibbus, G. Gardini det. 1994), id., 18.VI.1981, G. Gardini leg., Quercus cerris wood; 1 3 4 Ƥ ( C. gibbus, G. Gardini det. 1994), id., 18.VI.1981, G. Gardini leg., Fagus sylvatica wood; 1 3 ( C. gibbus, G. Gardini det. 1994), id., 19.VII.1981, P.

Brandmayr leg., Quercus cerris wood; 1 3 ( C. gibbus, G. Gardini det. 1994), id., 17.IX.1981, P. Brandmayr leg., Fagus sylvatica wood; 1 3 ( C. gibbus, G. Gardini det. 1994), id., 22.XI.1981, P. Brandmayr leg., Anemono- Fagetum; 1 3 1 Ƥ ( C. gibbus, G. Gardini det. 1994), id., 30.V.1982, P. Brandmayr, Quercus cerris wood; 2 3 1 Ƥ ( C. gibbus, G. Gardini det. 1994), id., 30.V.1982, P. Brandmayr leg., Fagus sylvatica wood; 1 Ƥ ( C. gibbus, G. Gardini det. 1994), id., 25.VI.1982, P. Brandmayr leg., Quercus cerris wood; 1 Ƥ, San Fratello, 28.IV.1982, G. Gardini & R. Rizzerio leg. Sicily: Palermo Prov.— 1 3, Caltavuturo, 450 m a.s.l., 30.V.1985, R. Rizzerio & S. Zoia leg., Quercus ilex wood; 1 Ƥ, Castelbuono, slope NE Pizzo Carbonara, 1500 m a.s.l., 31.V.1985, S. Zoia & R. Rizzerio leg., Fagus sylvatica wood; 1 Ƥ, Collesano, Piano Zucchi, 1050 m a.s.l., 31.V.1985, S. Zoia & R. Rizzerio leg., Quercus ilex wood; 1 3, id., road to Piano Zucchi, 1100 m a.s.l., 3.VI.1985, S. Zoia leg., hollow in Quercus ; 1 Ƥ, id., Scillato, 2.I.1994, P. Magrini leg.; 1 Ƥ, Corleone, Bosco della Ficuzza, 15.VI.1981, G. Gardini leg.; 4 Ƥ, id., near Case Cucco, 1000 m a.s.l., 29.V.1985, S. Zoia & R. Rizzerio leg.; 1 Ƥ, id., slope SE Monte Busambra, 650 m a.s.l., 30.V.1985, R. Rizzerio & S. Zoia leg.; 1 3, id., Bosco della Ficuzza, 800 m a.s.l., 2.V.2000, S. Zoia & F. Polese leg., Quercus wood; 1 Ƥ, Favorita, 12.IV.1990, P. Magrini leg.; 1 3, Palermo, Madonna dei Bosci, 14.VI.1981, G. Gardini leg.; 1 3, Petralia Sottana, Piano Battaglia, 1500 m a.s.l., 30.V.1985, R. Rizzerio & S. Zoia leg., Fagus sylvatica wood. Sicily: Siracusa Prov.— 1 3 1 Ƥ 1T ( C. siculus, M. Beier det.), Ferla, 10.IV.1962, Sichel & Alicata leg. (MBAC). Sicily: Trapani Prov.— 1 3, Isola di Favignana, 3.IV.1990, S. Zoia leg.; 1 Ƥ, Isola di Levanzo, Cala Tramontana, 4.IV.1990, S. Zoia leg.; 2 3 2 Ƥ ( C. siculus, M. Beier det.), Isola di Marettimo, 23.II.1972, D. Caruso & Costa leg., leaf litter under Fraxinus sp. (MBAC); 4 3 3 Ƥ, id., near Marettimo, 5.IV.1990, S. Zoia leg.; 1 3, id., Cala Cimitero, 5.V.1991, R. Argano leg.; 1 Ƥ, Isola di Pantelleria, Gadir, 31.III.1990, S. Zoia leg.; 1 3, id., Piano di Ghirlanda, 30.III.1990, S. Zoia leg., Quercus ilex wood; 1 Ƥ, id., 7.V.1994, F. Lo Valvo leg.; 2 3 3 Ƥ, Mazara del Vallo, Gorghi Tondi, 3.I.1995, G. Gardini leg.; 2 Ƥ, id., 30.IV.2000, S. Zoia & F. Polese leg., sieved under Quercus ilex ; 1 3 3 Ƥ, Scopello, Riserva Naturale dello Zingaro, 31.XII.1994, G. Gardini & S. Zoia leg., Quercus ilex wood; 1 3, id., 17.I.1997, B. Massa leg.; 1 3, id., 20.III.1997; 1 3, id., 25.IV.1997; 9 3 4 Ƥ, id., 23.V.1997; 1 3 4 Ƥ 1T, id., 13.VI.1997; 1 3 1 Ƥ, id., 14.IX.1997; 6 3 1 Ƥ, id., 30.VIII–15.IX.2001; 2 3 1T, id., 15–30.IX.2001; 1 3 2 Ƥ, id., 30.IX–17.X.2001; 4 Ƥ, id., 17–31.X.2001; 1 3 1 Ƥ 2T, id., 31.X–17.XI.2001; 1 3, id., 26.I–23.II.2002; 1 3, id., 23.II–16.III.2002; 1 Ƥ, id., 16.III–16.IV.2002. Sardinia: Cagliari Prov.— 1 Ƥ, Arbus, 26.X.1991, L. Fancello & P. Leo leg.; 1 Ƥ, Armungia, 16.X.1992, P. Leo leg.; 1 3, Cagliari, Cala Regina, 8.XII.1990, L. Fancello leg.; 2 Ƥ, Fluminimaggiore, 26.X.1991, L. Fancello & P. Leo leg.; 3 3 12 Ƥ 2T, id., 4 km S Fluminimaggiore, 2.IV.1997, S. Vit leg.; 2 3 1 Ƥ, Iglesias, Tempio di Antas, 29.III.1991, G. Gardini leg., Quercus ilex wood; 3 3, Isola San Pietro, Monte Guardia dei Mori, 10.VI.1989, R. Poggi leg. (MSNG); 1 Ƥ, Isola Sant’Antioco, Cala Lunga, 11.II.1984, L. Fancello & P. Leo leg.; 1 3 1 Ƥ, id., 4.II.1990, L. Fancello leg.; 2 3 2 Ƥ, Masua, Montecani, 25. V.1986, L. Fancello & P. Leo leg.; 1 Ƥ, Santadi, 17.XII.1993, L. Fancello & P. Leo leg.; 1 3, Sarroch, 31.III.1997, S. Vit leg., Olea roots; 1 3, Siliqua, Acqua Fredda, 27.II.1989 L. Fancello & P. Leo leg. Sardinia: Nuoro Prov.— 1 Ƥ, Dorgali, Cala Gonone, 23.V.1980, G. Gardini leg., Mediterranean scrub; 2 Ƥ, Esterzili, 25.I.1989, L. Fancello & P. Leo leg.; 1 3 1 Ƥ, Gairo, Valle del Riu Pardu, 7.VII.1984, C. Torti leg., Quercus ilex wood on limestone; 1 Ƥ, id., Gairo Cardedu, 26.VI.1984, C. Torti leg., Quercus ilex wood; 2 3, Macomer, Monte Sant’Antonio, 8.V.1993, L. Latella & M. Rampini leg.; 1 Ƥ, Perdasdefogu, 18.VI.1983, C. Torti leg.; 1 3, Perdasdefogu, near Monte Rasu, 600 m a.s.l., 4.IV.2008, C. Torti leg., leaf litter; 1 Ƥ, Tertenia, 23.IV.1992, P. Leo leg. Sardinia: Oristano Prov.— 2 Ƥ, Gonnostramatza, 2.XII.1989, P. Leo leg.; 1 3 1T, Paulilatino, 5 km SE Paulilatino, 200 m a.s.l., 3.IV.1997, S. Vit leg., Olea roots; 1 Ƥ 1T 1D, Santu Lussurgiu, Badde Urbara, 800 m a.s.l., 2.IV.1991, G. Gardini leg., sieved under Ilex . Sardinia: Sassari Prov.— 1 3, Alghero, Punta La Speranza, 26.VII.1975, S. Zoia leg.; 1 3, Isola Asinara, near Tumbarino, 13.X.1989, R. Poggi leg. (MSNG); 1 3 1 Ƥ, id., Tumbarino, 25 m a.s.l., V.2008, G. Ruzzante leg.; 1 Ƥ, Isola Maddalena, Spiaggia dei Monti della Rena, 8.IX.1987, R. Poggi leg. under Pistacia lentiscus L. (MSNG); 1 3, Padria, 16.XII.1986, L. Fancello & P. Leo leg.

Description of adults (Ƥ). Integument pigmented, carapace, tergites, chelicerae and pedipalps pale brown; marked hispid granulation on lateral surfaces of carapace, on cheliceral palm, on distal surface of chelal hand and on base of chelal fingers. Carapace 1.0 times longer than broad, subquadrate, posteriorly slightly constricted; anterior margin (figs 196–197) strongly dentate between median macrosetae, sometimes weakly prominent, rarely with epistome (3Ƥ from Cagliari: Sarroch and Fluminimaggiore; Ƥ from Oristano, Santu Lussurgiu); ocular area as in figs 198–199, anterior eyes with strongly convex lens (diameter 0.03–0.05 mm), rarely reduced (3 from Rome: Tolfa; Ƥ from Latina: Ventotene ; Ƥ from Foggia: Apricena; 3 from Taranto: Mottola; Ƥ from Siracusa: Ferla); posterior eyes with weak convex lens or reduced to ocular spot; both pairs mostly with tapetum; distance from anterior eyes to anterior margin of carapace 0.025–0.035 mm; normal carapacial chaetotaxy mm 4mm:6:4:2:2(18), macrosetae mostly short and thick (fine macrosetae in Ƥ from Foggia: Apricena); exceptions in carapacial chaetotaxy: 1 preocular microseta on each side in 3Ƥ from Naples: Camaldoli della Torre; 3Ƥ from Marettimo Is.; 3Ƥ from Catania: Fiumefreddo; 3Ƥ from Trapani: Scopello; 3Ƥ from Pantelleria Is.; 3Ƥ from Cagliari: Fluminimaggiore and Iglesias; posterior margin of carapace with one microseta on each side in Ƥ from Gravina di Puglia; 3Ƥ from Acitrezza: Is. Lachea; 3Ƥ from Cagliari: Masua; 3Ƥ from Asinara Is.; length of anteromedian macrosetae 0.06–0.08 mm. Chaetotaxy of tergites I–X 4:4:4:4:6:6:6:6:6:4. Chaetotaxy of sternites II–X 10:(3)10(3):(2)7(2):8:6:6:6:6:7; sternite II rarely with 9 setae, sternite III rarely with (3)9(3) setae, sternite IV rarely with (2)8–9(2) setae, sternite V rarely with 7 or 9 setae; genital opening of males flanked by 6–7 (rarely 8 or 9) setae on each side. Chelicerae (figs 200–201) 2.0–2.2 times as long as broad, palm with 6 setae and 2 microsetae laterally (one microseta in 3Ƥ from Marettimo Isl. and from Trapani: Scopello); fixed finger with 5–6 teeth (rarely up to 8) proximally reduced in size (rarely the distal one is smaller) and 4–6 proximal microtubercles; movable finger with 4–6 teeth proximally reduced in size (the distal one always larger) and 3–5 proximal microtubercles, without isolated subapical tooth (di); gl ratio 0.54–0.65; spinneret prominent, rounded apically, slightly smaller in males; rallum with 11 blades; serrulae interior and exterior respectively with 12 and 14 blades. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 3 marginal microsetae, II 4, III 5, IV 6; coxa II with 6–8 coxal spines (rarely up to 11), coxa III with 2–6 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 4.7–6.1 (3), 4.5–5.8 (Ƥ) times as long as broad; chela (figs 202–204) 4.5–6.0 (3), 4.0–5.2 (Ƥ) times as long as deep; hand of chela 1.8–2.4 (3), 1.7–2.15 (Ƥ) times as long as deep, clearly depressed at level of trichobothria ib-isb and with hump distad of ib-isb; fixed chelal finger with 14–23 teeth: rarely with 1 very small, triangular distal tooth, 12–20 large, triangular, pointed teeth with dental canals, weakly reclined and proximally reduced in size, and 1–7 proximal teeth with rounded apices, all with dental canals; base of fixed chelal finger mostly with 3–4 microtubercles; tip of fixed finger with a modified accessory tooth (td) on antiaxial face; fixed chelal finger at level of est-it with 4–6 teeth occupying 0.1 mm (distance between successive apices 0.019–0.022 mm); movable chelal finger with 10–17 teeth: rarely 1 very small distal tooth, 6–9 triangular, large, upright and pointed teeth with dental canals, and 5–10 proximal, rounded teeth gradually reduced in size, reaching as far as halfway between b and sb, without dental canals; base of movable chelal finger mostly with 2–4 microtubercles; coupled sensilla pc mostly at level of sb, rarely between b-sb; trichobothria as in figs 203–204, eb-esb-ist mostly placed in a straight line; basal apodeme of movable chelal finger strongly sclerotized, rectangular, squat, with subapical indentation; ratio of movable finger/hand of chela 1.3–1.5 (3), 1.2–1.4 (Ƥ); ratio of pedipalpal femur/movable finger 1.2–1.3 (3Ƥ); ratio of pedipalpal femur/carapace 1.1–1.3 (3Ƥ).

Measurements (in mm). Body length 1.0–1.5 (3), 1.2–1.6 (Ƥ). Carapace 0.29–0.39 × 0.28–0.39 (0.24–0.35 anteriorly) (3), 0.32–0.45 × 0.31–0.45 (0.27–0.41 anteriorly) (Ƥ). Chelicerae 0.23–0.325 × 0.11–0.155 (3), 0.26– 0.37 × 0.12–0.18 (Ƥ); movable finger length 0.115–0.17 (3), 0.135–0.18 (Ƥ). Pedipalp: femur 0.33–0.51 × 0.07– 0.10 (3), 0.37–0.58 × 0.08–0.11 (Ƥ); chela 0.48–0.72 × 0.105–0.145 (3), 0.53–0.81 × 0.12–0.195 (Ƥ); hand length 0.20–0.30 (3), 0.23–0.36 (Ƥ); movable finger length 0.28–0.41 (3), 0.30–0.45 (Ƥ).

Description of tritonymph. Integument with weak pigmentation and weak hispid granulation. Carapace 1.0 times longer than broad, anterior margin denticulate between median macrosetae, without epistome; anterior eyes with convex lenses, posterior ones reduced; chaetotaxy m 4m:6:4:2:2(18); posterior margin of carapace rarely with one microseta on each side (3Ƥ from Acitrezza: Lachea Is.); length of anteromedian macrosetae 0.05–0.06 mm. Chaetotaxy of tergites as in adults. Chaetotaxy of sternites II–X 5:(2)6(2):(1)6(1):7–8:6:6:6:6:7. Chelicerae 1.9– 2.05 times as long as broad, palm with 5 setae and 1 microseta laterally; fixed finger with 5–7 teeth and about 4 proximal microtubercles; movable finger with 3–5 teeth and about 3 proximal microtubercles, without isolated subapical tooth (di); gl ratio 0.57–0.59. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 2 marginal microsetae, II 4, III 5, IV 5; coxa II with 4–6 coxal spines, coxa III with 2–6 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 4.6–5.3 times as long as broad; chela 4.4–4.6 times as long as deep; hand of chela 1.9–2.0 times as long as deep, with a weak depression at level of trichobothrium ib and a hump distad of ib; dentition of chelal fingers of same form as in adults; fixed chelal finger with 14–16 teeth and 3–4 proximal microtubercles; tip of fixed finger with a modified accessory tooth (td) on antiaxial face; movable chelal finger with 6–8 triangular teeth, 3–5 proximal vestigial teeth and 2–3 microtubercles proximally; coupled sensilla pc distad of b; ratio of movable finger/hand of chela 1.3–1.4; ratio of pedipalpal femur/movable finger 1.2; ratio of pedipalpal femur/carapace 1.0–1.1.

Measurements (in mm). Body length 0.85–1.0. Carapace 0.27–0.32 × 0.27–0.32 (0.24–0.28 anteriorly). Chelicerae 0.205–0.25 × 0.10–0.13, movable finger length 0.10–0.13. Pedipalp: femur 0.28–0.36 × 0.055–0.07; chela 0.42–0.53 × 0.09–0.12; hand of chela length 0.17–0.23; movable finger length 0.24–0.29.

Remarks. Chthonius siculus was described by Beier (1961) from a male and a female from Sicily (Pachino: Grotta Calafarina). The species was subsequently recorded from Crete (Mahnert 1980), Spain (Zaragoza 1985), mainland Italy, Pontine Isl. and Sardinia (see Gardini 2000): all these records are based on the original description of Beier (1961), reproduced in Beier (1963a). Gardini (2008) redescribed the syntypes of C. siculus and noted the absence of an isolated subapical tooth (di) on movable cheliceral finger, thus showing that the records from Crete, from Spain (Valencia: Tous) and, in part, from Italy were based on misidentifications. The species has often been confused with C. gibbus .

Among the species of the Chthonius tetrachelatus group, the epigean C. siculus and C. tetrachelatus differ from each other in the shape of chelal hand (dorsally depressed at level of ib-isb and with hump distad of ib-isb in C. siculus , not depressed, or very weakly depressed, and without hump in C. tetrachelatus ), in the spacing between the chelal teeth of fixed finger at level of est-it with 4–6 teeth occupying 0.1 mm, distance between successive apices 0.019–0.022 mm in C. siculus ; with 3–4 teeth occupying 0.1 mm, distance 0.024–0.040 mm in C. tetrachelatus ) and in size (length of chela 0.48–0.72 (3) 0.53–0.81 (Ƥ) in C. siculus , 0.65–0.95 (3) 0.55–1.04 (Ƥ) in C. tetrachelatus ).

C. siculus is closely related to C. vachoni , an epigean species known from mainland France and western Liguria. C. siculus differs from C. vachoni chiefly in the number of setae on the posterior margin of the carapace (mostly with 2 macrosetae, rarely with 2 macro- and 2 microsetae in C. siculus , always with 2 macro- and 2 microsetae in C. vachoni ) and in the shape of the teeth in proximal half of chelal fingers [teeth reduced in size proximally, but still distinguishable as far as the base in C. siculus (figs 203–204); vestigial, broadly rounded proximally, only reaching as far as trichobothrium sb in C. vachoni (figs 268–269)]. Measurements and ratios are almost the same in both species.

The presence of only two macrosetae on the posterior margin of the carapace in C. siculus is assumed to be a character of taxonomic significance, despite the existence of a few populations with an additional microseta on each side (see above description and Callaini 1979, 1983) and a high individual and intrapopulational variation (Cagliari, Masua: 3Ƥ with 1 microseta on each side, Ƥ without microsetae; Acitrezza, Lachea Islot: 3 with 2 microsetae on each side, Ƥ with 1 + 0 microsetae, tritonymphs with 1 + 1 or 1 + 0 microsetae).

Figures

FIGURES 196 – 202. Chthonius (E.) siculus Beier, 1961 (Sicily, Catania, Fiumefreddo). 196, male, anterior margin of carapace; 197, female, id.; 198, male, anterolateral portion of carapace; 199, female, id.; 200, male, right chelicera; 201, female, id.; 202, male, tip of fixed chelal finger, dorsal view.

FIGURES 203 – 204. Chthonius (E.) siculus Beier, 1961 (Sicily, Catania, Fiumefreddo). 203, male, right chela, lateral view; 204, female, id. (Scale bar 0.1 mm).

FIGURES 282 – 285. Distribution maps for the Italian species of the Chthonius tetrachelatus group. 282, Chthonius (E.) tetrachelatus (Preyssler, 1790); 283, Chthonius (E.) siculus Beier, 1961 and C. (E.) vachoni Heurtault-Rossi, 1963; 284, Chthonius (E.) concii Beier, 1953 and C. (E.) lucanus Callaini, 1984; 285, Chthonius (E.) altamurae n. sp., C. (E.) apulicus Beier, 1958, C. (E.) elymus n. sp., C. (E.) grafittii Gardini, 1981, C. (E.) messapicus n. sp., C. (E.) poseidonis Gardini, 1993 and C. (E.) sardous Gardini, 2008.