Pseudohercostomus congoensis, Grootaert & Velde, 2021

Grootaert, Patrick & Velde, Isabella Van de, 2021, Understanding the tangled taxonomy of the genus Pseudohercostomus Stackelberg, 1931 (Insecta: Diptera: Dolichopodidae) with description of new species from Singapore and DR Congo, Raffles Bulletin of Zoology 69, pp. 324-335 : 330-333

Pseudohercostomus congoensis , new species

( Figs. 5 , 6A, B )

Paracleius echinatus ( Stackelberg, 1931) sensu Grichanov, 2004: 102 , diagnosis, fig. 67 (male terminalia lateral).

Pseudohercostomus echinatus in Grichanov & Brooks, 2017: fig. 148 (female terminalia dorsal).

Type material. Holotype male: DR CONGO: S.L. Edouard: r. Rwindi (1000 m), 16 February 1936, L. Lippens PARC NAT. ALBERT; det. P. Vanschuytbroeck, 1951: Pelastoneurus diversifemur Parent ; det. I. Grichanov, 2000 as Paracleius echinatus (Stackelberg) ; det. I. Grichanov as Pseudohercostomus echinatus Stackelberg. Male terminalia embedded in epoxy resin on microfilm on pin. (Coll. RMCA).

Paratypes: DR CONGO: 1 female: Embouch. Rutshuru L. Edouard S. 18 January 1936, Dr. H. Damas PARC NAT. ALBERT , det. P. Vanschuytbroeck, 1951: Hercostomus longipilus ; det. I. Grichanov, 2000 as Pseudohercostomus echinatus Stackelberg ; det. S.E. Brooks, 2000 as Pseudohercostomus echinatus . Female ovipositor in glycerine attached in microvial on pin. (prepared by S. Brooks and illustrated; in coll. RBINS) ; 1 female: Congo belge: P.N.U. Mabwe (lac Upemba ) (585 m.), 4 September 1947, Mis. G.F. de Witte, 734a det. P. Vanschuytbroeck, 1952: Hercostomus rhodesiensis Parent ; det. I. Grichanov as Pseudohercostomus echinatus Stackelberg ; det. S.E. Brooks, 2000 as Pseudohercostomus echinatus . Female ovipositor in glycerine attached in microvial on pin (in coll. RBINS) . Other material examined. MOZAMBIQUE: Sofala, Gorongosa Park , small lake, 18°56′39″S 34°26′35″E, 30 m, 19–30 April 2015, M. Hauser, A. Rung; 3 males ( CNC1107737 , CNC1107738 , CNC1107774 ) , 4 females ( CNC1107739 , CNC1107741 , CNC1107742 , CNC1107743 ) in Canadian National Collection; 1 male ( CNC1107740 ) , 2 females ( CNC1107775 , CNC1107776 ) in California State Collection of Arthropods , Sacramento ( CSCA) . All det. S. Brooks.

Description. Male ( Figs. 5 , 6A ). Length body: 4 mm; wing: 4.64 mm.

Head. Frons, face, and occiput grey dusted ( Fig. 5C ). Face entirely metallic green in ground-colour and narrowing towards clypeus.

Antenna. Scape brown, pedicel yellowish, postpedicel yellow on basal ⅓, apical ⅔ brownish yellow. Arista black. Pedicel with an apical crown of black bristles, dorsally with an extra row behind the apical row. A strong dorsal bristle 2× as long as pedicel. Postpedicel triangular (pointed) a little longer than high: 0.22 mm / 0.17 mm.

Thorax. Scutum metallic green in ground-colour, finely grey dusted. Pleura brownish, finely grey dusted. Acrostichals black, quadriserial, and the rows almost reaching to the base of the scutellum. Six dorsocentral bristles, anterior 2–3 rather short, remaining dorsocentrals increasing in length towards scutellum. Scutellum rectangular, longer than in P. singaporensis , new species. Metepimeron large, brownish black in ground colour and finely grey dusted, tough subshiny. Mid coxa anteriorly with a blackish stripe, dorsal part brown ( Fig. 5B ).

Legs yellow, except for mid coxa having a black stripe on anterior margin with dorsal side of coxa, while latter area is brownish. Bristling of legs ( Fig. 5A ) as in P. singaporensis , new species.

Mid coxa anteriorly with a blackish stripe, dorsal part brown ( Fig. 5B ).

Wing brownish grey tinged with dark brown veins. Squama white, with a marginal row of long bristles, black in anterior half, white and shorter in posterior half. Anteriorly with a single black bristle behind the marginal bristles. Haltere white. Abdomen. Tergites metallic green black in ground colour, with a very fine dusting. Bristling as in P. singaporensis , new species.

Male terminalia ( Fig. 6A ). A strong black basoventral epandrial bristle near base of hypandrium. A short apicoventral bristle on a short papilla. Ventral surstylus with a slightly thickened apical bristle and some short ventral bristles. Dorsal surstylus with an apical bristle and a dark subapical spine. Inner lobe of dorsal surstylus long, with a brown apical spine-like protuberance.

Female ( Fig. 6B ). Length: body: 4–5 mm; wing: 4.6–5 mm. Resembling male in most characters like the bristling on the legs. Face parallel-sided and broader than in male.

Female terminalia ( Fig. 6B ). Ovipositor dorsally with at least four rows of very strong black dorsal spines. Row of four strong pale bristles near base of acanthophorite.

Etymology. The new species is named after the type locality, DR Congo.

RAFFLES BULLETIN OF ZOOLOGY 2021

Comments. Pseudohercostomus congoensis , new species, closely resembles P. echinatus and seems to form a species complex with the latter. It differs in having a brown antennal scape, whereas the scape is yellow in P. echinatus . The mesoscutum is metallic green, while it is metallic blue with green reflections in P. echinatus . There are six dorsocentral bristles (anterior most short), while there are only four dorsocentrals in P. echinatus . The marginal bristles on the squama are black in the anterior half and white in the posterior half. In P. echinatus all marginal bristles are black and in addition, there are several long black bristles present behind the marginal bristles like in P. singaporensis , new species. The male terminalia in P. congoensis , new species, are different in having fewer and shorter dorsal bristles on the ventral surstylus, a different shape of the dorsal surstylus, and having a pointed brown tip of the inner lobe of the dorsal surstylus. In P. echinatus , as is illustrated by Brooks (2005: fig. 38), the ventral surstylus bears about eight longer ventral bristles and the inner lobe of the dorsal surstylus is shorter.

Pseudohercostomus congoensis , new species, is distinctly different from P. singaporensis , new species, in having quadriserial acrostichals and a postpedicel being triangular and slightly longer than high. In addition, there are six dorsocentral bristles ( Fig. 5B ) while in P. singaporensis there are only 4–5 dorsocentrals. In contrast to P. singaporensis , P. congoensis has the face entirely metallic green in groundcolour while in P. singaporensis the clypeus is mainly yellowish in ground-colour. The dorsal spines (acanthae) on the ovipositor are much smaller in P. singaporensis , new species ( Fig. 6C ) than in P. congoensis , new species ( Fig. 6B ).

Figures

Fig. 5. Pseudohercostomus congoensis, new species, male. Holotype [Lake Edward, Rwindi r., Albert National Park (Virunga National Park), DR Congo]. A, habitus lateral; B, mesoscutum dorsal; C, head. (RMCA, photo credit: I. Van de Velde)

Fig. 6. Pseudohercostomus. A, P. congoensis, new species, holotype male terminalia lateral view; B, P. congonesis, new species, female left acanthophore and cercus dorsal view, paratype; C, P. singaporensis, new species, acanthophore dorsal view, paratype (Kranji Marshes). Scale bars = 0.1 mm.