Key to species based on the worker caste (except for C. treubi apilis Forel, which was not examined)

1 Clypeus with distinct rugulae. Petiole rectangular, with angular corners in dorsal view (Fig. 3 a). Occipital carina developed as distinct ridge (Fig. 2 a).................................................................................. 2

- Clypeus relatively smooth and shining without distinct rugulae. Petiole broader anteriorly than posteriroly, but without angular corners (Fig. 3 b). Occipital carina undeveloped, without distinct ridge (Fig. 2 b).................................... 3

2 Clypeus with one longitudinal rugula on the median portion and two distinct pairs of longitudinal rugulae laterally. Dorsal promesonotum with dense reticulate sculpture (Fig. 4 a)................................................... brevis

- Clypeus with two distinct pairs of longitudinal rugulae, but lacking median rugula. Dorsal promesonotum with more open reticulate sculpture with shiny interspaces (Fig. 4 b).................................................... overbecki

3 Propodeal spines undeveloped (Fig. 12)................................................................ yappi

- Propodeal spines developed (Fig. 6)....................................................................... 4

4 Postpetiole strongly bilobed behind (Fig. 3 c)........................................................... walshi

- Postpetiole weakly bilobed (Fig. 3 b)....................................................................... 5

5 Metanotal groove distinct and deep (Fig. 5 a).......................................................... bouvardi

- Metanotal groove less distinct and deep (Fig. 5 b)............................................................ 6

6 Propodeal spines short and stout, their length shorter than the diameter of propodeal spiracles (Fig. 5 b)............. kojimai

- Propodeal spines long and slender, their length longer than the diameter of propodeal spiracles (Fig. 5 c)............. treubi