Key to Crematogaster species groups of the Malagasy region

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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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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
Fig. 3. A. Petiole ovo-rectangular C. telolafy. B. Petiole rectangular C. rasoherinae. C. Petiole broadly flared C. malahelo. D. Petiole oval C. dentata. E. Antennal club two-segmented C. razana. F. Antenna lacking distinct club C. ranavalonae; G. Median portion of clypeus with flange (cf) C. ranavalonae H. Promesonotal suture (pms) present, mesonotum (m) in dorsal view longer than pronotum (p) C. agnetis.
Fig. 4. A. Median portion of clypeus lacking flange C. kelleri. B. Propodeal spines absent; mesonotum (m) greatly raised with respect to pronotum and propodeum C. tsisitsilo. C. Posterior face of mesonotum (pfm) long; promesonotal suture absent C. kelleri. D. Promesonotum forming a straight plane, posterior face of mesonotum (pfm) abruptly sloping into metanotal groove, propodeal spines situated high on propodeum (pd) C. kelleri. E. Pronotum dorsally with distinct median longitudinal groove C. mafybe. F. Pronotum dorsally without median longitudinal groove C. lobata. G. Propodeum distinctly set off from promesonotum in lateral view C. malahelo. H. Propodeum not distinctly set off from promesonotum in lateral view C. dentata.

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