Eotrechus kerberos, Tran & Zettel & Sites, 2023

Tran, Anh Duc, Zettel, Herbert & Sites, Robert W., 2023, Revision of the genus Eotrechus Kirkaldy (Hemiptera, Heteroptera, Gerridae), with descriptions of six new species, Deutsche Entomologische Zeitschrift 70 (1), pp. 69-111 : 69

Eotrechus kerberos sp. nov.

Figs 8 , 9 , 10 , 26

Material examined.

Holotype: Laos • ♂ (apterous); Luang Prabang, Tham Seua, Tham Nam Lot, near cave entrance at wall; 19°26.095'N, 102°26.157'E; 4 Feb. 2005; H. Steiner leg.; 109/05; N-Lao-Europ. Cave Project 2005; NHMW.

Paratypes: Laos • 3 ♀♀ (apterous); same locality data as holotype; NHMW .

Description.

Size: apterous male (holotype), length 7.92, width 2.12; apterous females, length 8.00-8.17, width 2.28-2.38.

Colour (Fig. 8 ). Dorsum generally dark-brown to black, covered with golden pubescence. Anterolateral sides and posterior margin of head with yellow marks. Pronotum with three longitudinal yellow stripes (one median and two sublateral) all not reaching posterior margin of pronotum. Mesonotum with longitudinal yellow stripe tapering posteriorly but not reaching posterior margin, and two sublateral yellow marks confluent with median stripe on anterior third. Propleuron black, with a longitudinal yellow mark. Meso- and metacetabula black. Proacetabulum, mesopleuron, meso- and metacetabula with patch of reflective silvery pubescence. Antennae brown to dark-brown. All legs chiefly yellowish-brown. Venter of head mainly pale-yellowish, with a variably distinct brown marking in middle. Prosternum light-coloured. Mesosternum and anterior metasternum chiefly dark-brown to black, posterior metasternum brown. Abdominal venter brown and lateral sides of abdominal dark-brown to black.

Structural characteristics: Apterous male: Head width across eyes 1.58; interocular width 0.57; eye kidney-shaped in dorsal view, length of eye 0.48. Antennae ca. 0.9 × body length (7.36: 7.92), lengths of segments I-IV: 2.10: 1.81: 1.58: 1.87; segment I with four black spines in apical part. Pronotum broader than long, shorter than head length (0.98: 1.24). Lengths of mesosternum and metasternum: 2.20 and 0.63. Lengths of leg segments (femur: tibia: tarsal segment I: tarsal segment II) as follows: fore leg: 2.80: 2.75: 0.29: 0.39; middle leg: 7.17: 7.25: 0.42: 0.44; hind leg: 7.50: 8.75: 0.41: 0.45. Fore leg (Fig. 9A ): trochanter with two long, fine setae; femur strongly incrassate at basal part, with a large basal tubercle bearing a round spot of black, minute setae, and gradually tapering towards apex, length of femur ca. 5.2 × maximum width (2.80: 0.54), flexor side with a row of six long, stout setae; tibia straight at basal part, slightly curved at distal part, with long, brown, stout setae on extensor surface and shorter stout setae on apical margin; tarsus covered with long, soft, yellowish setae (denser on ventral surface). Middle and hind femora slender and slightly shorter than body; middle and hind femora, middle and hind tibiae with scattered short, brown spines. Claws stout, lengths of fore, mid- and hind claws: 0.15: 0.19: 0.18. Abdomen short, total length of abdominal sterna II-VII: 1.76, sterna II-VI medially grooved, the median groove widened in sterna III-V, and indistinct in sternum VI. Sternum VII distinctly longer than the length of two preceding sterna combined (0.67: 0.41), posterior margin with a deep median notch ca. 0.5 × the length of sternum VII (Fig. 10A ). Genitalia (Figs 9B-E , 10B-F ): abdominal segment VIII large; pygophore with lateral tubercles bearing a tuft of long, brownish setae, pygophore with a long, slender caudal projection, with apical third strongly bent dorsad; paramere small and with conical apex; proctiger with pointed posterolateral processes bearing long, brownish setae, ventral surface with short, pale setae.

Apterous female: Head width across eyes 1.61; interocular width 0.57; eye kidney-shaped in dorsal view, length 0.75. Antennae ca. 0.86 × of body length (6.89: 8.00), lengths of segments I-IV: 1.94: 1.66: 1.45: 1.84; segment I with five black spines subapically. Pronotum shorter than head length (0.96: 1.24). Lengths of mesosternum and metasternum: 2.15 and 0.73. Lengths of leg segments (femur: tibia: tarsal segment I: tarsal segment II): fore leg: 2.69: 2.51: 0.29: 0.41; middle leg: 7.08: 7.21: 0.44: 0.44; hind leg: 7.25: 8.29: 0.42: 0.42. Fore trochanter with 1-3 long, fine setae on ventral side (one specimen with an additional stout seta). Fore femur moderately thickened at basal part and gradually tapering towards apex, length ca. 7.5 × maximum width (2.69: 0.36), along flexor side with a row of 13-15 long, stout, black setae of irregular length, all shorter than greatest width of fore femur. Fore tibia straight with many long, stout setae on extensor surface and some shorter, stout setae on apical margin. Fore tarsus covered with long, soft, yellowish setae (denser on ventral surface). Middle and hind femur slender and shorter than body length; middle and hind femora, middle and hind tibiae with scattered short, brown spines. Claws stout, lengths of fore, mid- and hind claws: 0.16: 0.19: 0.18. Total length of abdominal sterna II-VII ca. 0.4 × body length (3.01: 8.00). Sternum VII ca. 1.3 × length of two preceding sterna combined (1.10: 0.84), posterior margin straight. Connexival apex of sternum VII truncate, slightly curved mesad, and lateral margin with a few long golden setae directed laterad (Fig. 10G, H ). Genitalia: not concealed by sternum VII; tergum VIII constricted on posterior part, then produced posterolaterad; proctiger elongate, with pointed apex and directed caudad (Fig. 10G, H ).

Macropterous morph: Unknown.

Remarks.

Eotrechus kerberos sp. nov. can be considered as the sister taxon of E. petraeus from Thailand because of many similarities, especially a very long caudal projection of the pygophore. However, a set of characteristics of the male distinguishes this new species from E. petraeus , as follows. The fore tibia of E. kerberos sp. nov. is slender, straight basally and slightly curved distally, whereas that of E. petraeus is distally thicker and more curved, with flexor side clearly bisinuate. Detailed structure of genitalia also shows a clear distinction between the two species. In E. kerberos sp. nov., the caudal projection of the pygophore is very slender, with the apical part evenly curved dorsad; the setal tufts on the lateral tubercles of the pygophore are pointing more laterally; the lateral processes of the proctiger are acute, pointing posteriorly; the ventral surface of the proctiger has shorter, pale setae; the paramere is short (length ca. 1.5 × width) and ovoid. In E. petraeus , the caudal projection of the pygophore is more triangular, with the apical third strongly bent dorsad; the setal tufts on the lateral tubercles of the pygophore are pointing more dorsad; the lateral processes of the proctiger are rectangular; the ventral surface of the proctiger has very long, dark setae; the paramere is more elongated (length more than 2.0 × width) and tapers apically.

Etymology.

The species is named after Eotrechus kerberos , the dog in Greek mythology that guards the gates of the nether world. The name refers to the collector’s notes, who observed the specimens sitting at a wall of a cave entrance; it is used as a noun in apposition.

Distribution.

Laos: Luang Prabang (Fig. 26 ).

Figures

Figure 8. Eotrechus kerberos sp. nov., habitus. A. Male holotype; B. Apterous female, paratype.

Figure 9. Eotrechus kerberos sp. nov., holotype. A. Left fore leg, ventral view; B, C. Pygophore, lateral and dorsal views; D. Proctiger, dorsal view; E. Paramere, lateral view (B-D. Same scale).

Figure 10. Eotrechus kerberos sp. nov. A-F. Holotype; A. Abdomen of male, ventral view (excluding genitalia); B, C, D. Pygophore, ventral, lateral, and dorsal views; E, F. Proctiger, lateral and dorsal views; G, H. Posterior part of abdomen of female, dorsal and lateral views (B-F. Same scale; G, H. Same scale).

Figure 26. Distribution records of species of Eotrechus. Circles represent E. longipes species group; squares represent E. petraeus species group; stars represent E. vietnamensis species group.