Key to species of Orthostigma (Whartonstigma)

1. Eye in lateral view 1.3 × as wide as temple medially (Fig. 10C). Precoxal sulcus crenulated and reaching posterior margins of mesopleuron (Fig. 10C). Body length 1.5–1.6 mm. Australia ........................ O. (W.) tropicale (Wharton) (♀ ♂)

- Eye in lateral view 1.7–2.0 × as wide as temple medially (Fig. 4B, 6B, 8C). Precoxal sulcus almost smooth and not reaching anterior and posterior margins of mesopleuron (Fig. 4B, 6B, 8C)................................................ 2

2(1). Head in lateral view distinctly and sublinearly narrowed dorsally (Fig. 6B). First flagellomere 3.8 × as long as its maximum width (Fig. 6D). Second flagellomere 3.9 × as long as its maximum width (Fig. 6D). First subdiscal cell of fore wing 3.0 × as long as its maximum width (Fig. 7D). Hind tibia 6.5 × as long its maximum subapical width (Fig. 7B). Body length 1.9–2.0 mm. Papua New Guinea ........................................................ O. (W.) longipede sp. nov. (♀)

- Head in lateral view weakly and roundly narrowed dorsally (Figs 4B, 8C). First flagellomere 2.8–3.2 × as long as its maximum width (Fig. 4D, 8E). Second flagellomere 2.4 × as long as its maximum width (Fig. 4D, 8E). First subdiscal cell of fore wing 3.8–4.0 × as long as its maximum width (Fig. 5D, 9F). Hind tibia 7.7 × as long its maximum subapical width (Fig. 5B, 9 C-D)................................................................................................. 3

3(2). First metasomal tergite 2.0 × as long as its apical width, widened towards apex (Fig. 9E). Mandible 1.1–1.2 × as long as its maximum width (Fig. 8D). Clypeus 2.0 × as wide as high (Fig. 8F). Marginal cell of fore wing 4.0 × as long as its maximum width (Fig. 9F). Propodeum with emerging carina from median longitudinal carina, with short emerging carinae (Fig. 9B). Body length 1.5–1.7 mm. Papua New Guinea ......................................... O. (W.) papuae sp. nov. (♀)

- First metasomal tergite 2.5–2.8 × as long as its apical width, almost parallel-sided (Fig. 5C). Mandible 1.5–1.6 × as long as its maximum width (Fig. 4C). Clypeus 3.0 × as wide as high (Fig. 4E). Marginal cell of fore wing 4.6 × as long as its maximum width (Fig. 5D). Propodeum without emerging carina from median longitudinal carina, without short emerging carinae and not reaching propodeal edges (Fig. 5A). Body length 1.5–1.7 mm. Australia ............... O. (W.) gallowagi (Wharton) (♀ ♂)