Key to subgenera and species-groups of Crematogaster in the Malagasy region

1. Antennae with 11 segments (including scape)......................................................................................2

– Antennae with 10 segments (including scape)........................................................................................ ......... Crematogaster hova -group (former subgenus Decacrema Forel, 1910; refer to Blaimer 2010)

2. Petiole ovo-rectangular (Fig. 3A), or rectangular (Fig. 3B), with postero-lateral denticles bearing long erect setae; antennae with a 2-segmented club (Fig. 3E).......................................................................... ..............................................................subgenus Orthocrema Santschi, 1918 (refer to Blaimer 2012b)

– Petiole of different shape, but never rectangular or ovo-rectangular (as e.g. in Fig. 3C, D); antennae with a 3-segmented club (as e.g. in Fig. 18A), or antennal club indistinct (as in Fig. 3F)................ 3

3. Median portion of clypeus with a flange (cf) projecting somewhat over mandibles (Fig. 3G); promesonotal suture (pms) present and mesonotum (m) in dorsal view longer than pronotum (p) (Fig. 3H); head round (Fig. 3F); eyes situated distinctly above midline of head in full-face view (Fig. 3F)................................. ... Crematogaster ranavalonae -group (former subgenus Oxygyne Forel, 1901; refer to Blaimer 2012a)

– Median portion of clypeus not protruding as a flange over mandibles (Fig. 4A); promesonotal suture often absent (e.g. as in Figs 7C; 12D; 15C; 18D), if present then mesonotum in dorsal view shorter than pronotum; head shape variable, rounded or quadrate (as e.g. in Figs 6A; 7A; 10A, D; 12A; 13A); position of eyes variable, situated at or above midline of head in full-face view ................... 4

4. Propodeal spines entirely absent (SPI 0.00), at most obtuse tubercules present (as e.g. in Figs 4B; 12C; 13B) .....................................................................................................................................................................5

– Propodeal spines present (SPI> 0.01), from minute dents to distinct spines (as e.g. in Figs 6B; 7B; 8B; 10E; 15B; 17C; 18C; 19C; 20B; 22B) ........................................................................................ 6

5. Mesonotum (m) greatly raised with respect to pronotum and propodeum (Fig. 4B); eyes larger (OI> 0.21); medium to small size (HW 0.66 - 1.03, WL 0.62 - 0.98); color orange or brown..................... .............................................................. C. tsisitsilo Blaimer, 2013 (refer to Blaimer & Fisher 2013)

– Promesonotum not much raised with respect to propodeum (as e.g. in Figs 12C, 13B); eyes small (OI <0.21) (as e.g. Figs 12A, 13A); medium to very large size (HW 0.80 - 1.43, WL 0.86 - 1.48); color brown or black ............................ C. degeeri -species-assemblage (refer to species key in this study)

6. In lateral view promesonotum forming a straight (or at most slightly rounded) plane (Fig. 4D); posterior face of mesonotum (pfm) long, distinctly set off from dorsal face (Fig. 4C), abruptly and steeply sloping into metanotal groove (Fig. 4D); propodeal spines always spiniform, very short to medium-sized (SPI 0.07 - 0.24), situated high on propodeum (pd) (Fig. 4D).......... C. kelleri -group (refer to Blaimer & Fisher 2013)

– Promesonotum variable, but never fitting above description; propodeal spines variable, minute denticles to distinct spines (SPI 0.01 - 0.26), usually situated lower on propodeum (as in Figs 6B; 7B; 8B; 10B, E; 15B; 17C; 18C; 19C) ................. C. degeeri -species-assemblage (refer to species key in this study)