Bioacoustics of Stygopholcus skotophilus

Redescription Male ( type locality; ZFMK (Ar 22196)) MEASUREMENTS. Total body length 5.5, carapace width 2.2. Distance PME–PME 160 µm ; diameter PME 150 × 180 µm ; distance PME–ALE 20 µm ; diameter AME 65 µm ; distance AME-AME 30 µm . Leg 1: 51.2 (13.7 + 0.9 + 13.6 + 20.3 + 3.2), tibia 2: 10.0, tibia 3: 8.2, tibia 4: 8.9; tibia 1 L/d: 62. COLOR (in ethanol). Carapace pale whitish to ochre-yellow, posterior half, ocular area, and clypeus slightly darker (light brown); sternum light brown, with dark brown margins and three pairs of dark triangular radial marks; legs pale ochre-yellow to light brown, without dark rings, without dark lines; abdomen pale gray, with distinct dark dorsal marks in posterior third and lateral marks in posterior half; ventrally with light brown genital area, indistinct diffuse purplish marks in front and behind genital area and in front of spinnerets. BODY. Habitus as in Fig. 2 . Ocular area slightly raised. Carapace with deep median pit ( Fig. 61 ) and pair of very shallow indistinct furrows diverging from pit to posterior margin of carapace. Clypeus unmodified. Sternum wider than long (1.50/1.05), unmodified. Abdomen oval, pointed at spinnerets; gonopore with six epiandrous spigots ( Fig. 62 ); ALS with two spigots each ( Fig. 69 ). CHELICERAE. As in Figs 51–52 , with pair of large frontal apophyses set with 2 modified hairs each, with 12 and 13 modified hairs each on frontal face ( Figs 63–64 ); with stridulatory ridges ( Fig. 71 ). PALPS. As in Figs 6–8 ; coxa with low retrolateral hump; trochanter barely modified; femur with distinct retrolateral process proximally, with stridulatory pick (modified hair) proximally on prolateral side ( Fig. 65 ); femur-patella joints shifted towards prolateral (arrows in Fig. 6 ); tibia very large, with two trichobothria; tibia-tarsus joints shifted towards retrolateral (arrows in Fig. 8 ); tarsus with exposed tarsal organ ( Fig. 66 ); procursus dorsally with curved hairs (distal third curved ‘upwards’), with strong hump on prolateral side; procursus tip with projecting dorsal sclerite, strong hinged ventral sclerite, and membranous central part with brush of hair-like processes on retrolateral side ( Figs 67–68 ), with weakly sclerotized cylindrical process on prolateral side bordering ventral sclerite (arrow in Fig. 45 ). Genital bulb ( Figs 47–50 ) with basal sclerite connecting to tarsus, small transparent dorsal process, and main sclerite consisting of retrolateral process and dorsal process; retrolateral process with bifid tip, distal part on ventral side thickened and heavily sclerotized; dorsal process with two finger-shaped tips, ventral tip simple, retrolateral tip with additional strong protrusion on ventral side. LEGS. With short spines ventrally on femur 1 in two rows ( Fig. 73 ), prolateral row ~23 spines, retrolateral row ~28 spines; without curved hairs; few vertical hairs; retrolateral trichobothrium of tibia 1 at 4%; prolateral trichobothrium absent on tibia 1, present on other tibiae; tarsus 1 with irregular platelets rather than with distinct pseudosegments. Male (variation) Males from most other localities paler, without lateral dark marks on abdomen, with fewer median dark marks (restricted to area above spinnerets), rarely without abdominal marks. Tibia 1 (N = 35): 11.1–14.7 (mean 12.8); tibia 2 (N = 37): 8.1–10.8 (mean 9.6); spines on femur 1: 32–58 (mean 52); modified hairs on each cheliceral basis (N = 74): 9–16 (mean 12.3); modified hairs on each cheliceral apophysis (N = 74): 1–5 (mean 2.7); chelicerae maximum width (N = 36): 0.74–0.86 (mean 0.80); procursus length (N = 37): 1.28–1.48 (mean 1.39); bulbal measures A–E: A (N = 20): 0.28–0.31 (mean 0.30); B (N = 20): 0.08–0.10 (mean 0.09); C (N = 20): 0.13–0.15 (mean 0.14); D (N = 20): 0.28–0.33 (mean 0.31); E (N = 15): 0.82–0.90 (mean 0.87); epiandrous spigots (N = 26): 5–8 (mean 6.1). Males from near Sedlari differ slightly in bulbal measure Asmaller (0.25–0.28) and bulbal measure B smaller (0.07–0.08); in addition, the smaller wart on the retrolateral bulbal process (arrow in Fig. 48 ) is more strongly developed. Female In general similar to male, but femur 1 without spines, with pair of indistinct processes posteriorly on carapace and pair of opposing poorly visible plates on abdomen; distance between processes/plates: 1.1. Tibia 1 (N = 36): 10.4–14.3 (mean 12.4); tibia 2 (N = 36): 7.2–10.3 (mean 9.0); epigynum width (N = 36): 1.02–1.46 (mean 1.21); epigynum length (N = 36): 0.54–0.68 (mean 0.61); epigynal measure F (N = 36): 0.42–0.58 (mean 0.47). Epigynum anterior plate semicircular, weakly protruding, with weak transversal furrows ( Figs 55–58 , 76 ), with internal structures visible in uncleared specimens: round anterior structure, short and indistinct parallel sclerites posteriorly wide apart; posterior plate short but wide. Internal genitalia ( Figs 53–54 , 147–148 ) with distinctive ventral arc ( Fig. 154 ; approximately as long as wide), with large pore plates ( Fig. 54 ). Females from near Sedlari differ in having the parallel sclerites posteriorly in the female internal genitalia closer together (epigynal measure F: 0.32–0.36; Figs 59–60 ) and slightly more distinct.