Orasema sixaolae

Baker, Austin J. & Heraty, John M., 2020, The New World ant parasitoid genus Orasema (Hymenoptera: Eucharitidae), Zootaxa 4888 (1), pp. 1-84 : 43

Orasema sixaolae species group

( Figs 21–25)

Diagnosis. Recognized by the following combination of characters: small-bodied (1.4–2.2 mm), antenna with 7 funiculars in both sexes, funiculars often wide and cup-shaped with a short peduncle, PTL:PTW = 1.6–4.2 (female), 5.0–7.8 (male). Generally, this group has a subcircular head shape, weak reticulate sculpture on the face and mesosoma, and dark body color.

Description. Female. Length 1.4–2.2 mm. Color. Scape, pedicel and anellus pale brown; flagellum brown. Maxilla and labium pale brown. Coxae brown. Wing venation pale brown. Gaster brown. Head. Scrobal depression shallow, laterally rounded, with transverse striae; anterior tentorial pit strongly impressed; anteclypeus distinct, broadly rounded. Occiput imbricate, emarginate in dorsal view. Scape not reaching median ocellus. Flagellum with 7 funiculars. Mesosoma. Notauli deep. Axilla dorsally rounded, on roughly the same plane as mesoscutellum; frenum and axillula smooth. Propodeal disc broadly rounded; callus smooth. Mesepisternum broadly rounded anterior to mid coxa. Upper and lower mesepimeron smooth; transepimeral sulcus distinct. Metepisternum laterally smooth. Propleuron convex. Postpectal carina weak. Hind coxa weakly reticulate. Fore wing marginal fringe relatively long; marginal vein pilose; stigmal vein slightly longer than broad. Metasoma. Petiole cylindrical, linear in profile.

Male. Length 1.5–2.0 mm. Scape pale brown; flagellum with 7 funiculars; anellus disc-shaped. Femora mostly brown, tips pale.

Phylogenetics. Orasema sixaolae and O. nebula , referred to as “nr. sixaolae” by Baker et al. 2020, are the only species molecularly sampled. Specimens of O. sixaolae sampled from Mexico, Costa Rica, Venezuela, and Ecuador are monophyletic with a crown age at about 4–7 MY and an average of 9.3% sequence variation between AHE-sequenced specimens, and O. nebula from Ecuador is the sister species. This species group is sister to O. monstrosa , which seems to share very few morphological similarities with the sixaolae group, warranting placement as its own group.

Key to species of the Orasema sixaolae species group

1) Curvature of eyes in frontal view appearing continuous with the curvature of head ( Figs 24B, 25B); female IOD:EYH>1.5; angle created by mesoscutellum, frenum, and propodeum less obtuse, closer to right angle, in lateral view ( Figs 24C, 25C).. ................................................................................................... 2

- Curvature of eyes in frontal view discontinuous with curvature of head, eyes appearing to bulge from sides of head ( Figs 22B, 23B); female IOD:EYH <1.5; angle created by mesoscutellum, frenum, and propodeum more obtuse in lateral view ( Figs 22C, 23C)............................................................................................... 3

2) Face and mesoscutal midlobe distinctly reticulate ( Fig. 24B, F); frenum in dorsal view <1/4 length of mesoscutellum ( Fig. 24F); female petiole longer/thinner (PTL:PTW = 3.1–4.1) (widespread Neotropical)....... Orasema sixaolae Wheeler & Wheeler

- Face smooth ( Fig. 25B) and mesoscutal midlobe imbricate anteriorly but transitioning to smooth dorsally ( Fig. 25E); frenum in dorsal view>1/4 length of mesoscutellum ( Fig. 25E); female petiole shorter/wider (PTL:PTW = 2.2) ( Ecuador).......................................................................................... Orasema tinalandia n. sp.

3) Flagellomeres 3–8 as wide as long ( Fig. 23D, E); female petiole longer than hind coxa ( Costa Rica and Ecuador)............................................................................................ Orasema nebula n. sp.

- Flagellomeres all longer than wide ( Fig. 22D); female petiole subequal in length to hind coxa ( Brazil).............................................................................................. Orasema brachycephala n. sp.