Key to Crematogaster species groups of the Malagasy region

This worker key is based on: Blaimer, B.B. & Fisher, B.L. 2013. Taxonomy of the Crematogaster degeeri-species-assemblage in the Malagasy region (Hymenoptera: Formicidae). European Journal of Taxonomy 51: 1-64 (DOI 10.5852/ejt.2013.51).

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 * Crematogaster
 * Ants of Madagascar

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
return to couplet #1
 * 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, or antennal club indistinct (as in Fig. 3F) . . . . . 3

3
return to couplet #2
 * 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, if present then mesonotum in dorsal view shorter than pronotum; head shape variable, rounded or quadrate; position of eyes variable, situated at or above midline of head in full-face view . . . . . 4

4
return to couplet #3
 * Propodeal spines entirely absent (SPI 0.00), at most obtuse tubercules present (as e.g. in Figs 4B) . . . . . 5


 * Propodeal spines present (SPI > 0.01), from minute dents to distinct spines . . . . . 6

5
return to couplet #4
 * 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 . . . . . Crematogaster tsisitsilo


 * Promesonotum not much raised with respect to propodeum; eyes small (OI < 0.21); medium to very large size (HW 0.80-1.43, WL 0.86-1.48); color brown or black . . . . . Crematogaster degeeri-species-assemblage

6
return to couplet #4
 * 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) . . . . . Crematogaster kelleri-species-assemblage


 * 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 . . . . . Crematogaster degeeri-species-assemblage