(Figs 118–121)

Type material

Holotype female (on slide, QMBA): AUSTRALIA, Western Australia, Kodjinup Nature Reserve, 34°22.6'S, 116°39.4'E, 19.xi.2002, G. Platner, sweeping forest, UCR PEET #02-0364.

Paratypes: AUSTRALIA: same data as holotype [1 male on slide and 1 female, 1 male on points, UCRC].

Description

FEMALE (holotype). Body mostly dark brown (gaster slightly lighter than head and mesosoma); petiole and appendages (except distal tarsomeres) light brown.

Vertex with scattered weak setae. Antenna (Fig. 118) a little shorter than body. Scape smooth, short, about as long as F2; F1 shorter than pedicel; F2 the longest funicle segment; F2–F6 more or less subequal in length (F5 slightly shorter), F6 the widest funicle segment; longitudinal sensilla only on F6 (1); clava a little longer than combined length of F4–F6, with 7 longitudinal sensilla.

Pronotum very short, the collar with 2 rows of strong setae on each lobe. Mesoscutum much wider than long, notauli not meeting posteriorly. Axillar seta not too strong. Scutellum as long as mesoscutum. Metanotum entire (Fig. 119).

Forewing (Fig. 120) about 4.1 x as long as wide, with 3 or 4 rows of setae behind venation; hypochaeta extending to posterior margin, longest marginal cilia about 4/5 forewing width; blade slightly infumate.

Metasoma about as long as mesosoma. Petiole about 2 x as long as wide. Ovipositor very short, not exserted beyond apex of gaster; ovipositor length: metatibia length about 0.7:1.

Measurements (holotype): Body: 693. Mesosoma: 303; mesoscutum: 106; scutellum: 109; petiole: 61; ovipositor: 206. Antenna: scape (excluding radicle): 61; pedicel: 46; F1: 40; F2: 64; F3: 48; F4: 48; F5: 45; F6: 51; clava: 170. Forewing: 800/197; longest marginal cilia: 155. Hind wing: 640/24. Legs (given as coxa, femur, tibia, tarsus): fore: 67, 157, 167, 209; middle: 70, 170, 251, 212; hind: 70, 206, 297, 248.

MALE (paratypes). Similar to female except for normal sexually dimorphic features, such as antenna (scape about as long as each of F2–F11 but longer than F1), genitalia (Fig. 121), and the following. Gaster dark brown, concolorous with head and mesosoma; petiole and appendages brown. Metasoma much shorter than mesosoma.

Diagnosis

This species is not similar to any other Australian members of the subgenus B. (Prosto) and differs significantly from the only other known species from the aligherini group, B. (P.) aligherini, in lacking the mediolongitudinal division of the metanotum and in the different arrangement of longitudinal sensilla on the female funicular segments, as indicated in the key. However, the following similarities between these two species allow for their inclusion in the same species group: the position of the scutellar placoid sensilla at the very anterior margin of the scutellum and especially the almost identical anatomy of the male genitalia, which are elongate.

Etymology "Nigugu" (treated here as a noun in apposition) stands for "keeping silent" in Russian.