Dibologonus oedipus, Mesibov, 2025

Dibologonus oedipus sp. nov.

Figs 9 D View Figure 9 , 13 View Figure 13 , 16 A View Figure 16

Type material.

Holotype. Male, Kosciuszko National Park ( NSW), 0.49 km NE of Rennix Gap, site HS 41-O-L 3 , -36.3579, 148.5060 ± 25 m, 1580 m, coll. Nicholas Porch, 2025-02 - 22, 1 m 2 litter sample from open shrubby subalpine grassland, NMV K 16511 GoogleMaps . Paratypes. 8 M, 17 F, details as for holotype, NMV K 16516 GoogleMaps ; 7 M, 2 F, same details but 0.58 km NNE of Rennix Gap, site HS 40-C-L 2 , -36.3561, 148.5046 ± 25 m, 1600 m, coll. Nicholas Porch and Aidan Fitt, 2025-02 - 09, closed shrubby subalpine woodland, NMV K 16526 GoogleMaps ; 1 M, same details but in 95 % EtOH, NMV K 16510 GoogleMaps ; 9 M, 1 F, same details but 0.52 km NNE of Rennix Gap, site HS 40-C-L 3 , -36.3579, 148.5060 ± 25 m, 1595 m, NMV K 16506 GoogleMaps .

Additional material.

16 M, 33 F, 3 J from 16 other sites. See Suppl. material 1 for details.

Diagnosis.

Smaller than D. sladei sp. nov. and D. major sp. nov. Distinguished from D. minor sp. nov. in having the major telopodite division at 1 / 3 telopodite height vs 2 / 3 height; distinguished from D. sladei sp. nov. by the expanded vs non-expanded apex of the solenomere; distinguished from D. major sp. nov. by the solenomere being well-separated from the medial branch, not obscuring it. In most male specimens, distinguished from D. sladei sp. nov., D. major sp. nov. and D. minor sp. nov. by modified right and left legs 13, 15 or 17.

Description.

As for the genus, with the following details. Colour in alcohol uniformly pale yellow, sometimes with fine brown speckling at collum and paranotal margins. Adult male / female approximate measurements: length 9 / 8 mm, midbody diameter 0.9 / 0.8.

Male with antenna almost reaching tergite 3 when manipulated dorsally; relative antennomere lengths 6> 3> 2> (4, 5); 6 widest. Posterior corners of paranota not projecting. Midbody metatergite width ca 1.2 × prozonite width. Midbody leg ca 1.7 × ring diameter. Legpairs 13, 15 or 17 may be greatly modified: prefemur, femur, postfemur and claw reduced in length, tibia and tarsus fused into swollen structure with dense ventral setation (Fig. 13 A View Figure 13 ). Brush setae dense, tapering to slightly curved point, without mid-height notch, on coxa / trochanter, prefemur, femur; sphaerotrichomes with slightly flattened globular base and pointed shaft on postfemur, tibia and tarsus.

Gonopod telopodites (Figs 9 D View Figure 9 , 13 B View Figure 13 ) straight, almost reaching legpair 5 when retracted. Telopodite divided at ca 1 / 3 telopodite height into medial branch and solenomere. Medial branch flattened, with small, tab-like posterolateral extension at ca 1 / 2 branch height; divided at ca 3 / 4 telopodite height into closely appressed medial and lateral processes: medial process shorter, flattened, tapering to blunt point; lateral process subcylindrical, tapering to blunt point a little distal to first division of solenomere. Solenomere well-separated from medial branch, divided at ca 7 / 8 telopodite height into medial and lateral processes, closely appressed, the lateral process tapering and terminating at level of prostatic groove opening on medial process. Medial process divided into leaf-like lateral portion curving medially, with small triangular extension on posterior margin, and well-separated, shorter, medial portion terminating in 3 small teeth, the central tooth having the prostatic groove opening and the most lateral tooth bluntly bifurcate.

Female a little smaller than male and with thinner, legs never modified; epigynum raised medially in low, rounded triangle; cyphopods not examined.

Name.

Noun in apposition, for the mythical king Oedipus of Thebes, whose name means “ swollen foot ”. See Remarks for notes on modified podomeres in this species.

Distribution.

Collected over a ca 125 km linear range from Namadgi National Park in the Australian Capital Territory to Kosciuszko National Park in New South Wales (Fig. 16 A View Figure 16 ), in subalpine woodland and shrubland from 1485 to 1880 m.

Remarks.

Modified legpairs 13, 15 or 17 are found in males across the range of D. oedipus sp. nov. and are not restricted to particular areas. Among the males with modified legs, all specimens with intact legs have modifications on both the left and right posterior legs on a particular ring. Six males have modifications on leg 13 (ring 9), one on leg 15 (ring 10) and 17 on leg 17 (ring 11). A single male (with intact legs) has no leg modifications. Variation in which legs are modified appears within populations: site HS 42-C-L 1 had three males with modified leg 13 and one with modified leg 17, while site HS 47-C-L 2 had one male without modifications, one with modified leg 15 and two with modified leg 17.

Similarly swollen distal podomeres were reported by Shear et al. (2022) in two males of the chordeumatidan Amplaria oedipus Shear, Nosler and Marek, 2022 from Cape Mountain, Oregon, USA. In both specimens the swollen podomeres were on legpairs 5 and 6.