Key to Brachyponera nigrita species group workers
This worker key is based on: Yamane, S. 2007. Pachycondyla nigrita and related species in southeast Asia (pp. 650-663). In Snelling, R.R., Fisher, B.L. and Ward, P.S. (eds). Advances in ant systematics: homage to E.O. Wilson – 50 years of contributions. Memoirs of the American Entomological Institute. 80:690 pp.
Yamane stated the following in regards to the key and the species it treats: In the present paper I deal with the large-sized species, which can be separated from the others by a combination of the following character states in the worker caste: 1) Head width over 0.9 mm in workers from mature colonies, 2) the number of ommatidia along the long axis of eye more than 10 (usually around 12; Figs. 1-3), 3) antennal scape long, in full-face view surpassing the posterior border of head by more than 1/4 of its length (Figs. 4-8; only in Brachyponera flavipes scape shorter), 4) all the flagellar segments of antenna longer than broad (this condition also applies to some medium- and small-sized species such as Brachyponera chinensis-complex), and 5) petiole relatively thick, with more or less flat dorsal surface in profile (transitional states between thick and thin petioles are found in other species). Among these the character states 2 to 5 may be associated with body size. I have primarily adopted the state 2 to separate the large-sized species from the others.
The Southeast Asian forms may be assigned to the three groups as follows:
Large-sized species: Brachyponera nigrita (continental Asia and Taiwan), Brachyponera wallacei (Sulawesi, Lombok and Bali), Brachyponera flavipes (Myanmar), Brachyponera pilidorsalis (Malay Peninsula and Borneo), and Brachyponera batak (N. Sumatra).
Medium-sized species: Brachyponera chinensis (widely distributed in S. E. Asia and temperate eastern Asia) and a few new forms.
Small-sized species: Brachyponera luteipes (continental Asia), Brachyponera jerdonii (N. India), and some new forms. Prof. P. S. Ward (personal communication) suggested that Brachyponera obscurans may also belong to this group.
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- Pronotal side, metapleuron above, propodeum extensively with rather strong rugae. Pronotal dorsum finely striate (Sulawesi, Lombok and Bali) . . . . . Brachyponera wallacei
- Mesosoma only weakly microsculptured . . . . . 2
return to couplet #1
- Antennal scape shorter (Fig. 5), surpassing the posterior margin of head by less than 1/4 of its total length. Legs yellowish brown to orangish, contrasting with jet black mesosoma (Myanmar) . . . . . Brachyponera flavipes
- Antennal scape longer, surpassing the posterior margin of head by more than 1/4 of its total length (Figs, 4, 6-8). Legs brown to dark brown, contrast with body color weaker . . . . . 3
return to couplet #2
- Mesosomal dorsum without standing hairs; standing hairs if any very few and shorter than width of funicular segment 1 of antenna (Sumatra) . . . . . Brachyponera batak
- Mesosomal dorsum usually with more than ten standing hairs, some of which are as long as width of funicular segment 1 . . . . . 4
return to couplet #3
- Mesopleuron often with a transverse groove; the groove sometimes incomplete but at least scar visible. Posterior faces of propodeum and petiole more strongly punctate. Gastral tergite 1 usually with more than ten standing hairs (Borneo; Malay Peninsula) . . . . . Brachyponera pilidorsalis
- Mesopleuron usually without such a groove; the groove if any vestigial. Posterior face of propodeum medially and petiole entirely smooth or very weakly punctate. Gastral tergite 1 with fewer standing hairs, the number, excluding those on the posterior margin of the tergite, being usually less than ten (Thailand, Vietnam, Myanmar) . . . . . Brachyponera nigrita