Crematogaster

Blaimer, Bonnie B., 2010, Taxonomy and Natural History of the Crematogaster (Decacrema) - group (Hymenoptera: Formicidae) in Madagascar, Zootaxa 2714, pp. 1-39 : 7

Key to the Subgenera of the Crematogaster of the Malagasy region: Workers

1. Antennae 10-segmented................................................................................................................................ Decacrema

- Antennae 11-segmented................................................................................................................................................ 2

2(1) Petiole in dorsal view rectangular, with four angular or acute corners ( Fig. 12 ); very small species (HW <0.75, WL <0.75) ............................................................................................................................................................ Mesocrema

- Petiole in dorsal view variable, but never rectangular; size variable............................................................................ 3

3(2) Petiole in dorsal view ovo-rectangular ( Fig. 13 ), with anterior corners rounded and posterior corners angular or acute, and dorsal face flat; dorso-lateral margins of metanotum carinate ( Fig. 14 ) or angular ( Fig. 15 ), with at least 1 long, flexible seta on either side; very small to small species (HW <0.90, WL <0.90) ............................ Orthocrema

- Petiole shape variable, if ovo-rectangular, then dorsal face concave; dorso-lateral margins of metanotum never carinate; size variable..........................................................................................................................................................4

4(3) Anterior margin of clypeus medially protruding as thin flange over mandibles ( Fig. 18 ), anterior part of clypeus transversely concave; subpetiolar tooth or protrusion absent, petiolar stalk narrow ( Fig. 16 b); petiole shape usually more or less slender and suboval ( Fig. 16 a), rarely flared or oval ................................................................... Oxygyne

- Anterior margin of clypeus never medially protruding over mandibles ( Fig. 19 ), anterior part of clypeus transversely convex; subpetiolar tooth or protrusion mostly present, variable in size and form, if close to absent ( Fig. 17 b), then petiole broadly flared anteriorly ( Fig. 17 a) and distinctly wider than long, never slender and suboval; otherwise petiole shape variable. ................................................................................................................................... Crematogaster

Figures

FIGURES 12 – 19. Key to the ‘ subgenera’ present in Madagascar. 12: petiole in dorsal view rectangular; 13: petiole in dorsal view ovo – rectangular; 14: dorso – lateral margins of mesonotum carinate; 15: dorso-lateral margins of mesonotum angular; 16 a: petiole slender (in dorsal view) and b: petiolar stalk narrow (in lateral view); 17 a: petiole flared (in dorsal view) and b: petiolar tooth absent (in lateral view); 18: mandibles with a single apical tooth, sickle-shaped; 19: mandibles with 5 teeth, broad (this type of mandibles also often with 4 teeth).