Chthonius ischnocheles (Hermann, 1804)

Gardini, Giulio, 2021, The Italian species of the Chthonius ischnocheles group (Arachnida, Pseudoscorpiones, Chthoniidae), with reference to neighbouring countries, Zootaxa 4987 (1), pp. 1-131 : 123-125

Key to adults of the Italian Chthonius species of the ischnocheles group.

1 Chelal fingers, especially the fixed one, with contiguous teeth along their entire length; teeth mostly low and inclined backwards ( Figs 33–40 , 150–157 ), rarely larger and more pointed ( Figs 365–372 ) or rectangular and apically truncated ( Figs 56–59 ).. 2

1’ Chelal fingers with more or less (see C. densedentatus , figs 110–116, and C. nicolosii , figs 342–349) widely spaced teeth, at least in the middle part of each finger; teeth mainly scalene triangle-shaped, reclined and apically pointed ( Figs 10–17 , 245–252 ), rarely long, sharp and slightly reclined ( Figs 195–202 ).............................................. 17

2 Posterior margin of carapace with 2–6 (rarely 8) macrosetae, without lateral microsetae............................. 3

2’ Posterior margin of carapace with 2 macrosetae and 1–2 lateral microsetae on each side............................ 12

3 Posterior margin of carapace with 2 macrosetae............................................................. 4

3’ Posterior margin of carapace with 4–6 (rarely 8) macrosetae................................................... 8

4 Anterior margin of carapace with 4 macrosetae, without preocular microsetae..................................... 5

4’ Anterior margin of carapace with 4 macrosetae and 1–2 preocular microsetae on each side........................... 6

5 Fixed chelal finger with acuminate, cuspidate and slightly reclined teeth with a convex distal side ( Figs 365-372 ); fixed chelal finger with 31–52 (♂ ♀), movable chelal finger with 26–38 (♂ ♀) teeth. (AT, CH, HR, SI, SK; IT: from Venezia Giulia to Lombardy; epigean species).............................................................. C. pygmaeus Beier, 1934

5’ Chelal teeth low, cuspidate and slightly reclined, with a sinuous distal side ( Figs 150-157 ); fixed chelal finger with 49–61 (♂ ♀), movable chelal finger with 37–49 (♂ ♀) teeth. (FR; IT: from Veneto to Liguria; epigean species).. C. guglielmii Callaini, 1986

6 Hypogean species with reduced eyes or anophthalmous; anterior margin of carapace strongly denticulate, without prominent epistome; pedipalps more slender: chela 5.3–6.35 (♂ ♀) times as long as deep; ratio of pedipalpal femur/carapace 1.3–1.55 (♂ ♀); length of chela 0.90–1.10 (♂ ♀) mm................................................................. 7

6’ Epigean species, anterior eyes with convex lens; anterior margin of carapace with prominent epistome; pedipalps less slender: chela 4.2–5.2 (♂ ♀) times as long as deep; ratio of pedipalpal femur/carapace 0.95–1.15 (♂ ♀); length of chela 0.56–0.77 (♂ ♀) mm. (FR; IT: from Liguria to Campania; epigean species)................................... .. C. ilvensis Beier, 1963

7 No eyes; chelicerae with 2–3 lateral microsetae; fixed and movable chelal fingers with 60–84 and 50–59 (♂ ♀) teeth respectively. (IT: Veneto, Romagna ; hypogean species)........................................ C. euganeus Gardini, 1991

7’ Eyes reduced, the anterior ones with flat lens; chelicerae with 1 lateral microseta; fixed and movable chelal fingers with 55–62 and 48–52 (♂ ♀) teeth respectively. (IT: Veneto; hypogean species)................................. C. herminii n. sp.

8 Posterior margin of carapace with 4 macrosetae............................................................. 9

8’ Posterior margin of carapace with 6 (rarely 4 or 8) macrosetae................................................ 11

9 Anterior margin of carapace with 4 macrosetae, without preocular microsetae; small sized epigean species: chela length 0.38– 0.51 (♂ ♀) mm, movable chelal finger length 0.225–0.34 (♂ ♀) mm; both fixed and movable chelal fingers at level of est-ist and st-t with 8–11 (♂ ♀) teeth occupying 0.05 mm; chelicerae without or with 1–2 lateral microsetae..................... 10

9’ Anterior margin of carapace with 4 macrosetae and 2 preocular microsetae on each side; medium sized hypogean species: chela length 0.88–1.0 (♂) mm, movable chelal finger length 0.595–0.68 (♂) mm; both fixed and movable chelal fingers at level of est-ist and st-t with 8–11 (♂) teeth occupying 0.1 mm; chelicerae with 3 lateral microsetae. (IT: Apulia; hypogean species)....................................................................................... C. inguscioi n. sp.

10 Chelicerae without lateral microsetae; eyes reduced, the anterior ones with flat lens; chela length 0.40–0.51 (♂ ♀) mm, movable chelal finger length 0.275–0.34 (♂ ♀) mm; movable chelal finger with coupled sensilla pc not on a tubercle. (GR, IL, LB, ES, PT, RO, TR; IT: from Latium to Basilicata, Sicily, Sardinia; epigean species).................... C jonicus Beier, 1931

10’ Chelicerae with 1–2 lateral microsetae; no eyes; length of chela 0.38–0.40 (♂ ♀) mm, movable chelal finger length 0.225–0.265 (♂ ♀) mm; movable chelal finger with coupled sensilla pc lodged on a noticeable tubercle. (IT: Sardinia; epigean species)...................................................................................... C. leoi Callaini, 1988

11 Medium-sized halophilic species: chela length 0.505–0.62 (♂ ♀) mm, movable chelal finger length 0.34–0.41 (♂ ♀) mm; anterior eyes reduced, with flat lens; chelicerae without lateral microsetae; anterior margin of carapace without preocular microsetae; posterior margin of carapace mainly with 6 (rarely 5–8) macrosetae; movable chelal finger with coupled sensilla pc not on a tubercle. (FR, GB, IE, PT; IT: Liguria, Latium, Sicily, Sardinia; epigean species)................ C. halberti Kew, 1916

11’ Small species of wooded and scrub habitat: chela length 0.31–0.43 (♂ ♀) mm, movable chelal finger length 0.21–0.28 (♂ ♀) mm; no eyes; chelicerae with 1–2 lateral microsetae; anterior margin of carapace mainly with 1 preocular microseta on each side (rarely without); posterior margin of carapace mainly with 6 (rarely 4) macrosetae; movable chelal finger with coupled sensilla pc on a weak tubercle. (IT: Liguria, Sicily, Sardinia; epigean species).................... C. caprai Gardini, 1977

12 Large hypogean species, eyes absent or reduced; chela length 1.0–1.76 (♂ ♀) mm, movable chelal finger length 0.68–1.20 (♂ ♀) mm; fixed chelal finger with 60–97 teeth; ratio of pedipalpal femur/carapace 1.35–1.9 (♂ ♀)........................ 13

12’ Medium-sized epigean species, anterior eyes with convex lens; chela length 0.57–0.84 (♂ ♀) mm, movable chelal finger length 0.39–0.56 (♂ ♀) mm; fixed chelal finger with 47–62 teeth; ratio of pedipalpal femur/carapace 1.0–1.3 (♂ ♀). (AT, DE, HR, SI; IT: from Venezia Giulia to Tuscany; epigean species)........................................ C. alpicola Beier, 1951

13 Anterior margin of carapace with 4 macrosetae and 1 or 2 preocular microsetae on each side; chelicerae with 2–3 (rarely 1) lateral microsetae; chela 6.1–7.5 (♂ ♀) times as long as deep; ratio of pedipalpal femur/carapace 1.35–1.85 (♂ ♀)........ 14

13’ Anterior margin of carapace with 4 macrosetae, without preocular microsetae; chelicerae without lateral microsetae; chela 8.0 (♂) times as long as deep; ratio of pedipalpal femur/carapace 1.9 (♂). (IT: Sardinia; hypogean species).... C. marciai n. sp.

14 Fixed chelal finger with 58–83 (♂ ♀) teeth, movable chelal finger with 39–53 (♂ ♀) teeth; fixed and movable chelal fingers at level of est-ist and st-t, respectively, with 5–9 and 4–7 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.011–0.018 and 0.014–0.023 (♂ ♀) mm respectively; ratio of pedipalpal femur/carapace 1.6–1.85 (♂ ♀)............... 15

14’ Fixed chelal finger with 83–97 (♂ ♀) teeth, movable chelal finger with 60–77 (♂ ♀) teeth; fixed and movable chelal fingers at level of est-ist and st-t, respectively, with 11–12 and 7–10 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.008–0.009 and 0.010–0.014 (♂ ♀) mm respectively; ratio of pedipalpal femur/carapace 1.35–1.55 (♂ ♀). (IT: Sicily; hypogean species).................................................................. .. C. multidentatus Beier, 1963

15 Anterior margin of carapace with 1 preocular microseta on each side; species from mainland Italy.................... 16

15’ Anterior margin of carapace with 2 preocular microsetae on each side; species from Sicily. (IT: Sicily; hypogean species).......................................................................................... C. gallettii n. sp.

16 No eyes; anterior margin of carapace with weak epistome; ratio of pedipalpal femur/carapace 1.7–1.85 (♂ ♀); species from western Alps. (FR; IT: Piedmont, Liguria; hypogean species).................................. C. italicus Beier, 1930

16’ Anterior eyes with flat lens, posterior eyes reduced to a pale cuticular area; anterior margin of carapace with prominent epistome; ratio of pedipalpal femur/carapace 1.6–1.7 (♂ ♀); species from southern Italy. (IT: Basilicata; hypogean species).................................................................................... C. caoduroi Callaini, 1987

17 Posterior margin of carapace with 2 or 4 macrosetae, without lateral microsetae.................................. 18

17’ Posterior margin of carapace with 2 macrosetae and 1–2 lateral microsetae on each side............................ 25

18 Posterior margin of carapace with 2 macrosetae, without lateral microsetae...................................... 19

18’ Posterior margin of carapace with 4 macrosetae (lateral macrosetae sometimes shorter than the median ones)........... 22

19 Anterior margin of carapace with 4 macrosetae, without preocular microsetae.................................... 20

19’ Anterior margin of carapace with 4 macrosetae and 1 (rarely 2) preocular microseta on each side..................... 21

20 Eyes present, epigean species; chelicerae with 1 lateral microseta; chela length 0.72–1.15 (♂ ♀) mm, movable chelal finger length 0.46–0.73 (♂ ♀) mm; chela 4.4–5.75 (♂ ♀) times as long as deep; fixed chelal finger with 24–41 (♂ ♀), movable chelal finger with 25–35 (♂ ♀) teeth; ratio of pedipalpal femur/carapace 1.3–1.45 (♂ ♀). (AT, CH, HR, HU, RO, SI, SK; IT: from Friuli to Trentino; epigean species)....................................................... C. carinthiacus Beier, 1951

20’ Anophthalmous hypogean species; chelicerae with 2 lateral microsetae; chela length 1.36 (♂) mm, movable chelal finger length 0.93 (♂) mm; chela 6.8 (♂) times as long as deep; fixed chelal finger with 52 (♂), movable chelal finger with 47 (♂) teeth; ratio of pedipalpal femur/carapace 1.75 (♂). (IT: Veneto; hypogean species)............................. C. gentianae n. sp.

21 Movable chelal finger with coupled sensilla pc lodged on a noticeable tubercle; chela length 0.56–1.08 (♂ ♀) mm, movable chelal finger length 0.39–0.74 (♂ ♀) mm. (IT: from Friuli to Trentino Alto Adige ; epigean/hypogean species)............................................................................................... C. agazzii Beier, 1966

21’ Movable chelal finger with coupled sensilla pc not on a tubercle; chela length 1.10–1.15 (♀) mm, movable chelal finger length 0.74–0.77 (♀) mm. (IT: Veneto; hypogean species......................................... C. paolettii Beier, 1973

22 Anterior margin of carapace with 1–2 preocular microsetae; chelicerae with 2–4 lateral microsetae; chela length 0.885–1.70 (♂ ♀) mm, movable chelal finger length 0.56–1.09 (♂ ♀) mm; ratio of pedipalpal femur/carapace 1.25–1.6 (♂ ♀)......... 23

22’ Anterior margin of carapace without preocular microsetae; chelicerae without lateral microsetae; chela length 0.45–0.62 (♂ ♀) mm, movable chelal finger length 0.30–0.41 (♂ ♀) mm; ratio of pedipalpal femur/carapace 1.05–1.25 (♂ ♀). (AT, CH, CZ, FR, HU, SK; IT: Liguria , Emilia , Latium; epigean species)......................................... C. ressli Beier, 1956

23 Hypogean species with reduced eyes; fixed chelal finger with 47–64 (♂ ♀) teeth; spinneret weakly raised (♂ ♀)......... 24

23’ Epigean species, both eyes with lens, that of the anterior ones convex; fixed chelal finger with 31–49 (♂ ♀) teeth; spinneret wide and semicircular (♂ ♀). (Europe, imported in SH, US; Italy: all regions; epigean)......... C. ischnocheles ( Hermann, 1804)

24 Fixed and movable chelal fingers at level of est-ist and st-t, respectively, with 3–5 and 4–6 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.018–0.034 and 0.016–0.030 (♂ ♀) mm respectively; chela length 1.09–1.67 (♂ ♀) mm, movable chelal finger length 0.72–1.09 (♂ ♀) mm. (IT: Campania; hypogean species)............. C. stammeri Beier, 1942

24’ Fixed and movable chelal fingers at level of est-ist and st-t, respectively, with 7–9 and 6–8 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.011–0.015 and 0.012–0.016 (♂ ♀) mm respectively; chela length 0.90–1.07 (♂ ♀) mm, movable chelal finger length 0.60–0.72 (♂ ♀) mm. (IT: Sicily; hypogean species)..................... C. nicolosii n. sp.

25 Chelal fingers with scalene triangle-shaped, reclined and apically pointed teeth ( Figs 84–91 , 304–308 ); both fixed and movable chelal fingers at level of est-ist and st-t with 4–8 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.011–0.034 (♂ ♀) mm.................................................................................26

25’ Chelal fingers with long, sharp, slightly reclined and widely spaced teeth ( Figs 203–211 ); 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 (♂ ♀) mm. (IT: Lombardy, Piedmont; hypogean species)............................................. C. horridus Beier, 1934

26 Tergite I with 4 setae; medium sized epigean (locally hypogean) species, anterior eyes with convex lens or with flat lens; chela length 0.715–1.20 (♂ ♀) mm, movable chelal finger length 0.46–0.81 (♂ ♀) mm; fixed chelal finger with 26–54 (♂ ♀) teeth, movable chelal finger with 23–47 (♂ ♀) teeth; ratio of pedipalpal femur/carapace 1.1–1.6 (♂ ♀)...................... 27

26’ Tergite I with 2 setae; large sized hypogean eyeless species; chela length 1.71–1.74 (♂ ♀) mm, movable chelal finger length 1.18–1.20 (♂ ♀) mm; fixed chelal finger with 60–64 (♂ ♀) teeth, movable chelal finger with 49–52 (♂ ♀) teeth; ratio of pedipalpal femur/carapace 1.5–1.85 (♂ ♀). (IT: Piedmont; hypogean species).................................. C. lanai n. sp.

27 Movable chelal finger with coupled sensilla pc lodged on a noticeable tubercle; chelal fingers teeth more widely spaced ( Figs 84–91 ): both fixed and movable chelal fingers at level of est-ist and st-t with 4–6 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.016–0.034 (♂ ♀) mm; anterior margin of carapace with 1 (rarely 2) preocular microseta on each side. (IT: from Lombardy to Liguria; epigean/hypogean species)................................. C. comottii Inzaghi, 1987

27’ Movable chelal finger with coupled sensilla pc not on a tubercle; chelal fingers teeth less widely spaced ( Figs 110–116 ): both fixed and movable chelal fingers at level of est-ist and st-t with 5–8 (♂ ♀) teeth occupying 0.1 mm, distance between successive apices 0.011–0.023 (♂ ♀) mm; anterior margin of carapace with 2 (rarely 1) preocular microsetae on each side. ( CH, FR, SI, HR, BA, AL, GR; IT: all regions except Sardinia ; mainly epigean species)................. C. densedentatus Beier, 1938

Figures

FIGURES 33–40. Chthonius alpicola Beier, 1951, slope of Mt. Matajur (Losaz, Udine). 33, male, right chela, antiaxial view; 34, male, detail of fingers at the chelal tip, antiaxial view; 35, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 36, male, detail of fingers at level of trichobothrium sb, antiaxial view; 37, female, right chela, antiaxial view; 38, female, detail of fingers at the chelal tip, antiaxial view; 39, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 40, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 150–157. Chthonius guglielmii Callaini, 1986, Vajo del Paradiso (Grezzana, Verona). 150, male, right chela, antiax- ial view; 151, male, detail of fingers at the chelal tip, antiaxial view; 152, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 153, male, detail of fingers at level of trichobothrium sb, antiaxial view; 154, female, right chela, antiaxial view; 155, female, detail of fingers at the chelal tip, antiaxial view; 156, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 157, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 365–372. Chthonius pygmaeus Beier, 1934, near Passo di Tanamea, 6.X.1997 (Lusevera, Udine). 365, male, right chela, antiaxial view; 366, male, detail of fingers at the chelal tip, antiaxial view; 367, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 368, male, detail of fingers at level of trichobothrium sb, antiaxial view; 369, female, right chela, antiaxial view; 370, female, detail of fingers at the chelal tip, antiaxial view; 371, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 372, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 56–59. Chthonius caprai Gardini, 1977, Vernazza (La Spezia). 56, male, right chela, antiaxial view; 57, male, detail of fingers at the distal half of right chela, antiaxial view; 58, male, detail of fingers at level of trichobothrium sb, antiaxial view; 59, female, right chela, antiaxial view.

FIGURES 10–17. Chthonius agazzii Beier, 1966, Buco delle Salamandre (Segusino, Treviso). 10, male, right chela, antiaxial view; 11, male, detail of fingers at the chelal tip, antiaxial view; 12, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 13, male, detail of fingers at level of trichobothrium sb, antiaxial view; 14, female, right chela, antiaxial view; 15, female, detail of fingers at the chelal tip, antiaxial view; 16, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 17, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 245–252. Chthonius ischnocheles (Hermann, 1804), Castiglione delle Stiviere (Mantova). 245, male, right chela, antiaxial view (hand granulation omitted); 246, male, detail of fingers at the chelal tip, antiaxial view; 247, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 248, male, detail of fingers at level of trichobothrium sb, antiaxial view; 249, female, right chela, antiaxial view (hand granulation omitted); 250, female, detail of fingers at the chelal tip, antiaxial view; 251, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 252, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 195–202. Chthonius horridus Beier, 1934, mine of Passobreve, 14.IV.2001 (Sagliano Micca, Biella). 195, male, right chela, antiaxial view; 196, male, detail of fingers at the chelal tip, antiaxial view; 197, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 198, male, detail of teeth at level of trichobothrium sb, antiaxial view; 199, female, right chela, antiaxial view; 200, female, detail of fingers at the chelal tip, antiaxial view; 201, female, detail of fingers at level of trichobothria st-t, antiaxial view; 202, female, detail of teeth at level of trichobothrium sb, antiaxial view.

FIGURES 84–91. Chthonius comottii Inzaghi, 1987, Baite Sedernello (Colzate, Bergamo). 84, male, right chela, antiaxial view; 85, male, detail of fingers at the chelal tip, antiaxial view; 86, male, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 87, male, detail of fingers at level of trichobothrium sb, antiaxial view; 88, female, right chela, antiaxial view; 89, female, detail of fingers at the chelal tip, antiaxial view; 90, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 91, female, detail of fingers at level of trichobothrium sb, antiaxial view.

FIGURES 304–308. Chthonius lanai n. sp. 304, female holotype, right chela, antiaxial view; 305, female holotype, detail of fingers at the chelal tip, antiaxial view; 306, female holotype, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 307, female holotype, detail of fingers at level of trichobothrium sb, antiaxial view; 308, male paratype, right chela, antiaxial view.

FIGURES 203–211. Chthonius horridus Beier, 1934, detail of chelal fingers dentition at level of trichobothria est-it and st-t, antiaxial view (setae omitted). 203, female, Frattura di Panvolio (Settimo Vittone, Turin); 204, female, Cavità del Molin dal Togn (Grignasco, Novara); 205, female, Grotta di Bercovei (Sostegno, Biella); 206, male, Tana del Diavolo (Trivero, Biella); 207, female, Tomba dei Polacchi (Rota d’Imagna, Bergamo); 208, male, id.; 209, female, Stampa dei Pagà (Monasterolo, Bergamo); 210, male, road to Presegno (Brescia); 211, female, Grotta Falsa Squarada (Sormano, Como).

FIGURES 110–116. Chthonius densedentatus Beier, 1938, Grotta Zinzulusa, 3.IV.2001 (Castro, Lecce) (unless otherwise stated). 110, female, right chela, antiaxial view; 111, female, detail of fingers at the right chelal tip, antiaxial view; 112, female, detail of fingers at level of trichobothria est-it and st-t, antiaxial view; 113, female, detail of fingers at level of trichobothrium sb, antiaxial view; 114, female holotype, detail of dentition at the left chelal fingers tip, antiaxial view (setae and sensilla af1-2, am1-2 omitted); 115, female holotype, detail of fingers at level of trichobothria est-it and st-t, antiaxial view (setae omitted); 116, female holotype, detail of fingers at level of trichobothrium sb, antiaxial view (setaeomitted).