Hylopachyiulus corylorum (Verhoeff, 1907)

Figs 1–3, 8A, B

Micropachyiulus corylorum Verhoeff, 1907: 459 (first description)

Mesoiulus corylorum (naming of the slides)

Hylopachyiulus corylorum— Attems (1926: 257, 258) (new combination)

Hylopachyiulus pygmaeus —Strasser (1966: 44) (synonymization)

Hylopachyiulus likanus Attems, 1926: 244, syn. nov.

Material examined: Micropachyiulus corylorum Verhoeff, 1907 . Lectotype male (herein designated): (ZSM-A- 20041388) Mesoiulus corylorum Verh.: a slide with male parts,: 1.-5. Mundt., 6.-9. B. Gp. (Fig. 2).

Paralectotypes: ZSM-A- 20041272 Micropachyiulus corylorum Verh. Wehrdrüs. (Wehrdrüsen) Muskel: juvenile female mounted in total, without anterior part of the body (Fig. 1F); ZMB/ Myr 4597: adult female in ethanol, Assling (= Jesenice in Slovenia) (Fig. 1 A–C); ZMB/ Myr 13063 a/b: juvenile female structures of the anterior part of the body mounted on a microslides, Assling (= Jesenice in Slovenia) (Fig. 1D, E) .

Hylopachyiulus likanus Attems, 1926 syn. nov. 1 dissected male in 3 body sections and head; 6 females, 1 micro-preparation (NHMW3180), Croatia, Velebit Mountain, Štirovača, leg. Attems.

Non type material: 1 male (NHMW9434), 2 females broken, one missing posterior part (NHMW9435), Croatia, Velebit Mountain, Šatorina, leg. Attems ; 1 female, 1 juvenile (NHMW9436), Croatia, Velebit Mountain, Dundović Padež, leg. Attems ; 2 females (NHMW9437), Slovenia, Ribnica (= Reifnitz), Velika Gora, leg. Attems.

Diagnosis. H. corylorum is habitually similar to H. pygmaeus; both species are characterized by the absence of ommatidia and the presence of a long and acuminate preanal process. H. corylorum can easily be distinguished from H. pygmaeus by the robust preanal process slightly curved ventrad (vs. slender and straight, with thin distal half in H. pygmaeus) and by some gonopod structures viz., promeral lobes of almost the same height (vs. promeral mesal lobe robust and much higher than lateral one in H. pygmaeus), or short and hook-shaped mesomeral process much shorter than opisthomeral one (vs. slender mesomeral process half as long as the posterior gonopod in H. pygmaeus). H. corylorum differs significantly from H. ocellatus sp. nov. in both external and gonopod structures viz., the absence of ommatidia (vs. presence in H. ocellatus sp. nov.), the presence of a long and sharp preanal process (vs. short and blunt in H. ocellatus sp. nov.) and the presence of a short and hook-shaped mesomeral process (vs. short and subtriangular in H. ocellatus sp. nov.). From both congeners, H. corylorum also differs in presence of much more pronounced lateral margin of anterior part of the posterior gonopods, in anterior view.

Synonymization of H. likanus under H. corylorum . After examining and comparison of the type, near topotype and non-type material of H. corylorum and H. likanus, we realize that both species show almost identic gonopods and external characters, viz. characteristic hook-shaped mesomeral process, general shape of the promere with the same height of the promeral lobes, body sizes, as well as a robust preanal process. Since we could not find any differences between these two taxa we synonymise H. likanus under the older name corylorum .

Descriptive notes. Small blind species. Male (NHMW9434): 6.6 mm long, vertical diameter of largest body ring ca. 0.45 mm, body with 34 podous rings + 3 apodous rings + telson. Females 10–13 mm long, vertical diameter of largest body ring 0.6–0.8 mm, body with 40–50 podous rings + 0–2 apodous rings + telson.

Colouration: (Figs 1A, 3A). All specimens pale yellowish.

Head: (Figs 1B, 3B). With two frontal setae, ommatidia absent in all specimens. Antennae 0.71 mm long (male NHMW9434), length 157% of vertical diameter of the largest body ring. Length of antennomeres I–VIII (in mm): 0.05 (I), 0.13 (II), 0.11 (III), 0.14 (IV), 0.14 (V), 0.08 (VI), 0.03 (VII), and 0.03 (VIII).

Body rings: (Figs 1 A–C, 3). With short metazonal setae. Length of midbody setae ca. 15% of vertical diameter of rings.

Telson: (Figs 1C, 3C). Epiproct with a protruding and sharp preanal process, slightly curved ventrad, covered by long dorsal and lateral setae.

Legs: First pair of legs modified, hook-shaped (Fig. 2A). Legs without ventral pads.

Gonopods: (Figs 2B, C, 8A, B). Promere (Figs 2B, 8A) higher than posterior gonopods with a broad base and slightly protruding lateral margin, faintly sinuous, curved posteromesad. Basal half caudally equipped with mesal (ml) and lateral (ll) lobes of the same height. Distal third posteriorly with a thin, lamellar and denticulated ridge (dr). Posterior gonopod (Figs 2C, 8B) with a short, slender, and distally hook-shaped mesomeral process (m). Opisthomeral lamella (l) spoon-shaped, hyaline, presenting strong serrations on the margin and short dense setae on its mesal surface. Solenomere (s) short, protruding from the margin of the lamella and with a bifurcate tip.

Distribution. Slovenia: Jesenice (=Assling) (type locality) (Verhoeff 1908), Velika Gora near Ribnica (= Reifnitz) (Attems 1929), Okroglina, Snežnik, (Strasser 1966a); Italy: Hill near Ragogna, Autonomous region Friuli–Venezia Giulia (Enghoff, pers. comm.); Croatia: Štirovača, Velebit Mountain (type locality of H. likanus syn. nov.) (Attems 1927), Šatorina, Velebit Mountain (Attems 1929), Dundović Padež, Velebit Mountain (present study) (Fig. 9, green circles).

Notes. Verhoeff (1908) stated that he found specimens in Corylus humus. Strasser (1966a) stated that specimens were found in Fagus forest, under the deeply embedded stone.

See discussion for comments on the presence of a small rod-like process (r) (Fig. 8B) in the distal part of the opistomeral process.

Type locality. Jesenice (=Assling), Slovenia.