Oberthuerella nigrescens Benoit

Buffington, Matthew L. & Noort, Simon van, 2012, Revision of the Afrotropical Oberthuerellinae (Cynipoidea, Liopteridae), ZooKeys 202, pp. 1-154 : 48-53

Oberthuerella nigrescens Benoit Figures 23-25

Oberthuerella nigrescens Benoit, 1955: 288

Description.

Coloration of head, mesosoma, and metasoma black to dark brown; legs reddish brown. Sculpture on vertex, lateral surface of pronotum and mesoscutum present, deeply foveate laterally on head, pronotum, mesoscutum.

Head. Broadly triangular, in anterior view. Pubescence on head present, dense setae covering head. Sculpture along lateral margin of occiput absent. Gena (measured from compound eye to posterolateral margin of head) short, ratio of length of gena to length of compound eye in dorsal view <0.3, in dorsal view. Sculpture of gena present, with distinct fovea. Lateral margin of occiput defined by distinctly angled, raised, sharp carina. Occiput (except extreme lateral margin) smooth. Ocelli small, ratio of maximum diameter of a lateral ocellus to shortest distance between lateral ocelli 0.2-0.4. Anterior ocellus close to posterior ocelli, posterior margin of anterior ocellus behind or subcontiguous with a transverse line running through anterior margins of posterior ocelli. Relative position of toruli close to ocelli, ratio of vertical distance between inner margin of torulus and ventral margin of clypeus to vertical distance between anterior ocellus and torulus <2.0. Median keel of face present, short, not extending beyond toruli. Vertical carina adjacent to ventral margin of torulus absent. Facial sculpture almost entirely foveate, with smooth, narrow, dorso-ventral triangular area along midline. Facial impression absent, face flat. Antennal scrobe absent. Anterior tentorial pits large. Vertical delineations on lower face absent. Ventral clypeal margin laterally, close to anterior mandibular articulation, distinctly angled. Ventral clypeal margin medially emarginate. Clypeus horizontally striate. Malar space adjacent to anterior articulation of mandible evenly rounded, foveate. Malar sulcus absent. Compound eye close to posterior ocellus, ratio of distance between compound eye and posterior mandibular articulation to distance between posterior ocellus and compound eye> 1.2. Compound eye, in dorsal view, distinctly protruding from the surface of the head, particularly laterally. Pubescence on Compound eye absent. Orbital furrows absent. Lateral frontal carina of face absent. Dorsal aspect of vertex deeply foveate. Posterior aspect of vertex foveate. Hair punctures on lateral aspect of vertex absent. Posterior surface of head almost flat, not deeply impressed.

Antenna. Articulation between flagellomeres in antenna connate with articles broadly joined. Female antenna composed of 11 flagellomeres. Female F1 shorter than F2; black. Flagellomeres of female antenna cylindrical, not widened towards apex, non-clavate. Placoidal sensilla absent. Distal flagellomeres of female antenna not conspicuously enlarged compared to proximal flagellomeres.

Macrosculpture on lateral surface of pronotum present, dorsomedially foveate, laterally foveate-costate. Pubescence on lateral surface of pronotum present, sparse, consisting of few short hairs. Anterior flange of pronotal plate distinctly protruding anteriorly, smooth. Carinae extending posteriorly from lateral margin of pronotal plate absent. Lateral pronotal carina present. Pronotal crest absent. Dorsal margin of pronotal plate (in anterior view) rounded. Lateral margin of pronotal plate defined all the way to the dorsal margin of the pronotum. Pronotal plate wide, almost as wide as head.

Mesoscutum. Mesoscutal surface convex, evenly curved. Sculpture on mesoscutum present, foveate-punctate, with remnants of transverse costae. Notaulus present, marked by deep furrows, slightly increasing in width posteriorly. Median mesoscutal carina absent. Anterior admedial lines present, flat, indistinct, with adjacent cuticular surface foveate. Median mesoscutal impression present, long, reaching over 1/2 length of mesoscutum. Parascutal carina distinctly sinuate, posteriorly ending in posteroventrally directed projection.

Mesopleuron. Horizontally strigulate, with striae converging on remnant fovea along posterior margin of sclerite. Subpleuron entirely smooth with few long white setae along ventral, posterior margins. Lower mesopleuron medially smooth, setose; costate laterally, ventrally. Epicnemial carina present on ventral half of mesopleuron; shagreened, ventrally bulbous near mesosternum. Lateroventral mesopleural carina present, marking abrupt change of slope of mesopectus. Mesopleural triangle absent. Subalar pit large and well defined, lying in posterior end of subalar groove. Speculum present, smooth anteriorly, microcarinate posteriorly. Mesopleural carina absent.

Scutellum. Dorsal surface of scutellum foveate-areolate. Circumscutellar carina absent. Posterior margin of axillula marked by distinct ledge, axillula distinctly impressed adjacent to ledge. Lateroventral margin of scutellum posterior to auricula entirely smooth. Dorsoposterior part of scutellum produced posteriorly into sharp spine, greater than 1.0 × length of petiole. Dorsal part of scutellum entirely foveate. Scutellar plate absent. Scutellar foveae present, three, each lateral fovea with two longitudinal divisions, central fovea smooth, resulting in transverse row of 7 longitudinally elongate subfovea. Longitudinal scutellar carinae absent. Single longitudinal carina separating scutellar foveae absent. Posterolateral margin of scutellum rounded. Lateral bar distinctly foveate, wide.

Metapectal-propodeal complex. Metapectal cavity anterodorsal to metacoxal base present, ill-defined. Anterior margin of metapectal-propodeal complex separated from mesopleuron by deep, broad, uninterrupted marginal impression. Posteroventral corner of metapleuron (in lateral view) rounded, not drawn out posteriorly. Anterior impression of metepimeron present, narrow, linear impression, not broadened ventrally. Posterior margin of metepimeron distinct, separating metepimeron from propodeum. Subalar area slightly broadened anteriorly, without longitudinal division indicated. Calyptra present, blunt, lobe-like, polished posteriorly with setiferous punctures anteriorly. Dorsellum present, two strong medial fovea, laterally strongly excavated with fine pubescence in lateral depressions. Anterior impression of metepisternum, immediately beneath anterior end of metapleural carina, absent. Pubescence consisting of few scattered hairs on posterior part of metapleuron and lateral part of propodeum. Propodeal spurs present, foveate. Lateral propodeal carinae present, not reaching scutellum. Ventral end of lateral propodeal carina reaching nucha, carinae separated from each other. Inter propodeal carinae space lightly setose, foveate. Petiolar foramen removed from metacoxae, directed posteriorly. Horizontal carina running anteriorly from lateral propodeal carina present. Lateral propodeal carina straight, sub-parallel. Calyptra, in lateral view, elongate. Propodeum relatively short, not drawn out posteriorly. Calyptra, in posterior view, dorsoventrally elongate.

Legs. Pubescence posterolaterally on metacoxa sparse to moderately dense, confined dense hair patch absent. Microsculpture on hind coxa absent. Longitudinal carina on the posterior surface of metatibia absent. Metafemoral spine present, elongate, extending distally as low keel along ventral femoral margin. Ratio of first metatibial segment to remaining 4 segments greater than 1.0.

Forewing. Pubescence of forewing absent on basal half of wing, sparse distally. Apical margin of female forewing rounded. Rs+M of forewing tubular. Mesal end of Rs+M vein situated closer to posterior margin of forewing, directed towards posterior end of basalis. Vein R1 tubular along at least basal part of anterior margin of marginal cell. Basal abscissa of R1 (the abscissa between 2r and the forewing margin) of forewing as broad as adjacent wing veins. Forewing entirely lightly infuscate. Marginal cell of forewing membranous, similar to other wing cells. Areolet present, complete. Hair fringe along apical margin of forewing absent.

Petiole. Slightly elongate, 1.5 –2× longer than wide. Surface of petiole longitudinally costate, ventral keel absent. Posterior part of female petiole not abruptly widened. Ventral flange of annulus of female petiole absent.

Metasoma. Setal band (hairy ring) at base of tergum 3 absent, base of metasoma glabrous. Tergum 3 distinctly smaller than tergum 4. Posterior margin of tergum 3 slightly but distinctly concave. Posterior margin of tergum 4 arcuate. In lateral view, sternum 3 exposed, ventral border of T2-T7 visible. Sculpture on metasomal terga present, dorsally finely punctate, posteriorly with distinct bands of setiferous pits. Syntergum absent, all postpetiolar terga free. Annulus absent. Peg-like setae on T6-T7 absent. Posteroventral cavities of female metasoma T7 present, setose. Female posteroventral margin of T6-T7 gently sinuate. Terebrum and hypopygium (in lateral view) straight, pointing posteriorly.

Ovipositor. First valvula of ovipositor narrowing gradually, not broadened apically, smooth at tip. Ovipositor clip absent.

Diagnosis.

Distinguished from other species of Oberthuerella by having the head, mesosoma and metasoma all dark brown/black (in other species, the metasoma is yellow/orange); the only other species that shares this trait is Oberthuerella kibalensis , and this species can be differentiated based on slight color differences in setae on the hind legs and metasoma, where in Oberthuerella kibalensis the setae are silvery-white, and in Oberthuerella nigrescens , the setae are a golden-yellow. Also, in Oberthuerella kibalensis , the lateral aspect of the pronotum is deeply costate, and in Oberthuerella nigrescens , the same is foveate with remnant traces of costae.

Distribution.

Democratic Republic of Congo. Link to Distribution Map. [http://hol.osu.edu/map-full.html?id=181560]

Material examined.

Holotype, female: DEMOCRATIC REPUBLIC OF THE CONGO: Eala, IX-1935, J. Ghesquière, Mus. Cong. Cyn1-2 (deposited in MRAC).