Stenus hippoamicus Janák, 2022

Janák, Jiří, 2022, Four new species and additional records of the genus Stenus of southern Africa (Coleoptera: Staphylinidae: Steninae), Zootaxa 5174 (4), pp. 331-356 : 334-337

Stenus hippoamicus Janák , sp. nov.

( Figs. 1–14, 21–22 , 67–68 , 73–74 )

Type locality. South Africa, KwaZulu-Natal Province, Ndumo Game Reserve .

Type material. Holotype ♂: SOUTH AFRICA: KwaZulu-Natal: “ South Africa, KwaZulu-Natal Province, Ndumo Game Res., Nyamithi pan, 26°54.0´S, 32°16.0´E, 26–27.i.2016, J. Janák lgt.”, “ HOLOTYPUS Stenus hippoamicus sp. nov., J. Janák det. 2021” ( TMSA) . Paratypes: 1 ♂, 1 ♀: same data as holotype ( JJRC) ; 4 ♂, 3 ♀: “ South Africa , KwaZulu-Natal, Isimangaliso Wetl. Park, reeds, Sta. Lucia, 28°22.2´S, 32°24.7´E, 24.i.2016, J. Janák lgt.” (2 ♂, 2 ♀ in TMSA, 2 ♂, 1 ♀ in JJRC). All with additional label “ PARATYPUS Stenus hippoamicus sp. nov., J. Janák det. 2021” .

Description (n = 10). Body length 3.0– 3.6 mm (M 3.3 mm, HT 3.3 mm), fore parts 1.5–1.9 mm (M 1.8 mm, HT 1.8 mm). Macropterous, black, slightly shiny, fore parts coarsely and densely punctate, abdomen moderately finely and moderately sparsely punctate; pubescence distinct, recumbent ( Fig. 1 ). Antennae black. Basal segments of maxillary palpi yellow, apical half of segment 3 brownish, segment 4 dark brown or blackish. Legs black, basal segments of meso- and metatarsi brownish. Clypeus black, labrum black, sparsely pubescent.

Head slightly narrower than elytra (R 0.90–0.98, M 0.99, HT 68.4/68.8 = 0.99), frons broad (average distance between eyes 29–33), with two distinct longitudinal furrows, median part as broad as each of lateral parts, moderately elevated, not extending to level of inner eye margins; punctation moderately coarse and dense, diameters of punctures as large as basal diameter of second antennal segment; antennal tubercles, lateral parts posteriorly and median part narrowly impunctate, slightly shiny, with faint reticulation.Antennae moderately short, when reflexed not extending to posterior margin of pronotum, penultimate segments slightly transverse.

Pronotum strongly convex, slightly longer than broad (R 1.08–1.15, M 1.10, HT 54.4/50.2 = 1.08), broadest slightly before middle, distinctly constricted behind; no distinct impression present; punctation coarse and dense, diameter of average punctures as large as maximal diameter of second antennal segment.

Elytra subquadrate, slightly broader than head, about as long as broad or slightly longer than long (R 0.99–1.07, M 1.02, HT 68.8/68.4 = 1.01), shoulders slightly oblique, sides at first straight or slightly emarginated, then slightly rounded and widened behind, distinctly constricted in posterior two fifths, posterior margin moderately emarginate (sutural length 59–71); sutural and humeral impressions distinct; punctation slightly finer and more densely than on pronotum, diameter of punctures slightly smaller than maximal diameter of second antennal segment, interstices markedly smaller than diameter of punctures.

Abdomen broad, basal constriction of segments deep, tergite 7 with distinct membranous fringe apically; punctation on basal tergite 3 moderately coarse and dense, interstices mostly about as large as diameter of punctures or smaller, on remainder of abdomen fine, but distinct; punctures on tergite 5 as large as one medial eye facet, punctures on tergite 7 markedly finer. Legs moderately slender, metatarsi half as long as metatibiae, segment 1 shorter than segments 2 and 3 combined, slightly shorter than last, segment 4 not bilobed. Pronotum and elytra very shallowly reticulate or only with traces of microsculpture (visible at magnification of 70 x), abdomen densely and shallowly reticulate.

Male. Sternite 6 and 7 medio-posteriorly flattened, sternite 7 in this area finely and slightly more finely punctured as in remaining parts of sternite, sternite 8 with broad subtriangular emargination in about posterior fifth ( Fig. 2 ). Sternite 9 moderately emarginated, with short apicolateral teeth ( Fig. 9 ). Tergite 10 subrounded apicomedially ( Fig. 10 ). Aedeagus 0.68–0.74 mm long (n = 5, M 0.72 mm, HT 0.74 mm), narrowed apically, in about two thirds and before apex slightly emarginated ( Figs. 3–8 ), internal sac unmodified, formed by long, slightly curved tube ( Figs. 13–14 ), parameres not reaching apex of median lobe ( Figs. 3–8 , 21–22 ), slightly widened apically, with numerous (about 15–21) setae.

Female. Sternite 8 slightly emarginated posteriomedially. Tergite 10 slightly emarginated posteriomedially ( Fig. 12 ). Valvifer shortly acute posteriolaterally ( Fig. 11 ).

Differential diagnosis. This new species belongs to the mendicus group (species with not bilobed tarsomere 4, abdomen with paratergites, first abdominal tergites without keels, aedeagus with expulsion hooks).

The general shape of aedeagus of S. hippoamicus Janák , sp. nov. with no traces of ventromedial carinae and with a curved tube in internal sac is similar as in S. galla Rougemont, 1981 (distributed in Ethiopia), S. naivashensis Puthz, 1971 (distributed in Kenya) and S. decellei Puthz, 1971 (distributed in D.R. Congo), but the new species differs from all this species by more parallel body and broader head (width of head/width of elytra ratio: S. hippoamicus Janák sp. nov.: 0.90–0.98, S. galla : 0.80–0.82, S. decellei : 0.86, S. naivashensis : 0.83 by holotype according Puthz (1971) and 0.81 in examined male) and also from: S. galla ( Figs. 15, 18, 23–24 ) by broader apical part of median lobe, narrower parameres, markedly longer expulsion hooks and shorter apicolateral teeth of sternite 9, from S. naivashensis ( Figs. 17, 20 ) by shorter parameres, apicolaterally slightly emarginated sides of median lobe and shorter apicolateral teeth of sternite 9 and from S. decellei ( Figs. 16, 19 ) by laterally rounded and apicolaterally slightly emarginated sides of median lobe.

S. hippoamicus Janák , sp. nov. differs from four species of the S. mendicus group distributed in South Africa ( S. arenicola , S. pretoriensis , S. gerardi , S. separatus ) externally by narrower, more parallel body and mainly by absence of ventromedial carinae of median lobe of aedeagus (this part is more less regularly convex); from S. arenicola also by less shiny, smaller body with more finely punctate pronotum and shorter antennae; from S. pretoriensis also by broader head in relation to elytra and smaller unpunctured area on head; from externally similar S. gerardi also by smaller body, less dense punctation of elytra with not confluent punctures and by S. separatus also by markedly less shiny body and less apically narrowed abdomen.

Material used for comparison:

S. galla : Paratype ♂: ETHIOPIA, Lake Zuaï , Shoa, 27.ix.1971, G. de Rougemont ( SMNS, coll. Puthz); photographs of 2 ♂ paratypes taken by Robert Douglas ( Courtesy of Oxford University Museum of Natural History) ,

S. naivashensis : 1 ♂: Naivasha , Kenia, 15.i.73 ( SMNS, coll. Puthz)

S. decellei : Holotype ♂: COLL. MUS. CONGO, Kalundwe (N. E. Gandajika), riv. Lualu, 25.iii.1959, J. Decelle ( MRAC).

Derivatio nominis. The name of the new species is derived from hippopotamus and amicus, indicating that both type localities are inhabited by rich populations of hippos ( Fig. 67 ).

Distribution. S. hippoamicus Janák , sp. nov. is currently known only from the Ndumo National Reserve and Santa Lucia (part of iSimangaliso Wetland Park) in KwaZulu-Natal Province, South Africa ( Figs. 73–74 ).

Bionomics. The type specimens were found in Ndumo ( Fig. 68 ) and St. Lucia ( Fig. 67 ) by treading of shores of streams.

Figures

FIGURE 73. Distribution of Stenus mendicus group in southern Africa. Empty forms = published records; filled forms = new records;? = uncertain identification.

FIGURE 74. Distribution of Stenus decellei Puthz, S. galla Puthz, S. hippoamicus Janák, sp. nov. and S. naivashensis Puthz.

FIGURES 1–12. Stenus hippoamicus Janák, sp. nov.: 1–3, 9–10, holotype, 4–8, 11–12, paratypes; 1, habitus; 2, abdomen ventral; 3, 7, 8, aedeagus dorsal, transmitted light; 4–6 aedeagus in reflected light (4, dorsal; 5, 1/3 lateral; 6, lateral); 9, male sternite 9; 10, male tergite 10; 11, female, valves; 12, female tergite 10. Scale 1 mm: 1–2; scale 0.5 mm: 3–12.

FIGURES 13–24. 13–14, 21–22: Stenus hippoamicus Janák, sp. nov.: 13–14, 21, holotype; 22, paratype from St. Lucia. 15, 18, 23–24: Stenus galla Rougemont, paratypes. 16, 19: Stenus decellei Puthz, holotype. 17, 20: Stenus naivashensis. 13–14, basal part of aedeagus with internal sac; 15–17, aedeagus dorsal; 18–20, sternite 9, 21–24, apical part of aedeagus and expulsion hooks. Scale 0.1 mm: 13–14, 21–24; scale 0.5 mm: 18–20.

FIGURES 67–72. Localities where Stenus species were collected. S. hippoamicus Janák, sp. nov. (67, St. Lucia; 68, Ndumo); S. volkerputhzianus Janák, sp. nov. (69, Himeville, 70, Tugella river); S. hessei L. Benick, S. capicola L. Benick, S. depressiusculus L. Benick, S. cf. grandipennis L. Benick, 1933 (71, Olifantsbos); S. spiniferoides Janák, sp. nov. (72, Langvlei).