Key to the world species of Masona van Achterberg, 1995

The following key has been modified and expanded from that provided in van Achterberg (1995). Only the males of M. prognatha and M. similis are known. Despite the fact that timpaynei is treated as incertae sedis in the subfamily Neorhacodinae in the present paper, we report it here as [ Masona] timpaynei, and we include it into the following key to facilitate identification.

1. Female winged; head orthognathous; tibia not expanded .................... [M.] timpaynei Quicke, 2019 incertae sedis in Neorhacodinae ( Ichneumonidae)

– Female wingless; head prognathous (Figs 1, 6, 10, 12A); tibia bulbous (Figs 1, 2B, 7A, 8B) ........ 2

2. Scutellum present (Figs 1B, 5A, 7A) ................................................................................................ 3

– Scutellum absent (Figs 10A, 11A) .................................................................................................... 5

3. Propodeum strongly bulbous, with carinate apophyse (Fig. 2A); pronotum with a strongly projecting flange (Fig. 6A); antenna with 14 flagellomeres; body pale yellowish (Fig. 7A); Brazil .................. ....................................................................................................... M. popeye Quicke & Chaul, 2019

– Propodeum not strongly bulbous, without carinate apophyse (Fig. 2B); pronotum without a strongly projecting flange (Fig. 6B); antenna with 11 or 16 flagellomeres; body brown or yellowish (Figs 1, 2B, 5, 6B); USA (Southeast & Puerto Rico) .................................................................................... 4

4. Antenna with 11 flagellomeres; apical flagellomere 5 × as long as wide (Fig. 5A); head in dorsal view not strongly narrowing posteriorly, almost parallel-sided (Fig. 5A); occipital carina simple, not foveolate (Fig. 5A); body pale yellowish (Figs 5, 6B); body length 1.2 mm; Puerto Rico ................ .................................................................................................... M. neon Dal Pos & Martens sp.nov.

– Antenna with 16 flagellomeres; apical flagellomere 2.2 × as long as wide (Fig. 1A); head in dorsal view strongly narrowing posteriorly (Fig. 1B); occipital carina foveolate (Fig. 1B); body dark brown (Figs 1, 2B); body length 1.8 mm; USA (Southeast) ......... M. bulbofemoralis van Achterberg, 1995

5. Length of third flagellomere 1.3–1.5 × its width; antenna as long as combined length of head and mesosoma (Figs 10A, 11A); head in dorsal view more robust, slightly narrowed posteriorly (Figs 10A, 11A); occipital carina short in lateral view, not reaching ventral margin of gena (Fig. 10B); precoxal sulcus present, superficially impressed (Fig. 11B); male pterostigma present, weakly defined (male of M. wow sp. nov. unknown); USA ................................................................................................. 6

– Length of third flagellomere about 2.5× its width; antenna somewhat longer than combined length of head and mesosoma; head in dorsal view less robust, narrowed posteriorly (van Achterberg 1995: figs 735, 741); occipital carina longer in lateral view, almost reaching external ventral margin of gena (van Achterberg 1995: fig. 733); precoxal sulcus absent; male pterostigma absent (male of M. infuscata unknown); Australia ..................................................................................................... 7

6. Head smooth, without processes (Fig. 10); pronotum not projecting into a flange, round (Fig. 10); USA (Southeast) ....................................................................... M. prognatha van Achterberg, 1995

– Head with two processes on the frons, about half the distance between eyes and occipital carina (Figs 11B, 12A); pronotum with a strongly projecting flange (Fig. 11B); USA (Southwest) ............ ................................................................................................... M. wow Dal Pos & Martens sp. nov.

7. Antenna with 12–14 flagellomeres; metasoma completely pale yellowish; fore basitarsus in dorsal view more robust (van Achterberg 1995: fig. 734); head in dorsal view slightly less narrowed posteriorly (van Achterberg 1995: fig. 735); length of body of female 0.9–1.2 mm ............................................ .......................................................................................................... M. similis van Achterberg, 1995

– Antenna with 16 flagellomeres; metasoma (except first tergite) more or less dark brown; fore basitarsus in dorsal view less robust (van Achterberg 1995: fig. 742); head of female in dorsal view slightly more narrowed posteriorly (van Achterberg 1995: fig. 741); length of body of female about 1.7 mm ....... ..................................................................................................... M. infuscata van Achterberg, 1995