Key to Crematogaster degeeri group workers

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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

  • Propodeal spines absent, reduced to small tubercules or denticles, or short triangular spines with SPI < 0.07; if very rarely propodeal spines spiniform and longer (SPI 0.08-0.10), then small species (HW 0.72-0.88, WL 0.79- 0.91), color dirty-yellow, montane rainforest habitats . . . . . 2
  • Propodeal spines longer, distinctly spiniform and SPI > 0.07; size and color variable; all habitats . . . . . 9

2

return to couplet #1

  • Eyes small (OI < 0.21) and largely confluent with lateral head margin . . . . . 3
  • Eyes larger (OI > 0.20) and distinctly protruding from lateral head margin . . . . . 6

3

return to couplet #2

  • Pronotum dorsally with a distinct median longitudinal groove, medium to large species (HW 0.98-1.43, WL 0.98-1.48) . . . . . Crematogaster mafybe
Crematogaster mafybe casent0141219 p 1 high.jpg
  • Pronotum dorsally without median longitudinal groove, size variable . . . . . 4

4

return to couplet #3

Crematogaster lobata casent0101773 profile 1.jpg
  • Propodeum with short triangular spines or sharp minute denticles . . . . . 5

5

return to couplet #4

  • Antennal scapes very short (SI 0.67-0.75), not reaching head margin; mesonotum usually with posterolateral denticles . . . . . Crematogaster masokely
Crematogaster masokely casent0068954 p 1 high.jpg
  • Antennal scapes variable, but usually longer (SI 0.69-0.82) and about reaching head margin; mesonotum usually without posterolateral denticles . . . . . Crematogaster dentata (in part - also #7) (in part - also #13)
Crematogaster sewellei dentata casent0059574 profile 1.jpg

6

return to couplet #2

  • Eyes very large (OI 0.24-0.29), situated above midline of head in full-face view; antennal scapes mostly longer (SI 0.77-0.87), reaching or surpassing head margin; bicolored: head and thorax yellowish to dark orange, metasoma with A4-7 brown or black . . . . . Crematogaster sewellii
Crematogaster sewellii casent0101599 profile 1.jpg
  • Eyes mostly smaller (OI 0.20-0.26), usually situated at midline of head in full-face view; antennal scapes variable, but often shorter (SI 0.69-0.83), just about or not reaching head margin; color variable . . . . . 7

7

return to couplet #6

  • Propodeum usually distinctly set off from promesonotum in lateral view and often with posterolateral denticles; promesonotum with sparse erect pilosity ( < 8 setae); petiole often much wider than long (PTWI 1.18-1.52), and strongly flared . . . . . 8
  • Propodeum not distinctly set off from promesonotum (in lateral view), never with distinct posterolateral denticles; promesonotum usually with abundant erect pilosity (>8 setae); petiole not much wider than long (PTWI 0.95-1.31), moderately flared . . . . . Crematogaster dentata (in part - also #5) (in part - also #13)
Crematogaster sewellei dentata casent0059574 profile 1.jpg

8

return to couplet #7

  • Medium-sized species (HW 0.86-1.03, WL 0.92-1.08); propodeal spines short and triangular (SPI 0.03-0.07); pronotum with sharp lateral margins . . . . . Crematogaster malahelo
Crematogaster malahelo casent0317768 p 1 high.jpg
  • Small species (HW 0.72-0.88, WL 0.79-0.91); propodeal spines longer (SPI 0.06-0.10); pronotum lacking sharp lateral margins . . . . . Crematogaster alafara
Crematogaster alafara casent0492837 p 1 high.jpg

9

return to couplet #1

  • Predominant color either orange, brown or black . . . . . 11

10

return to couplet #9

  • Medium to large species (HW 0.87-1.03, WL 0.98-1.22); antennal scapes very long (SI 0.91-1.01), easily surpassing head margin . . . . . Crematogaster bara
Crematogaster bara casent0116613 p 1 high.jpg
  • Small species (HW 0.60-0.86, WL 0.66-0.93); antennal scapes short (SI 0.71-0.83), not or about reaching head margin . . . . . Crematogaster maina
Crematogaster maina casent0134845 p 1 high.jpg

11

return to couplet #9

  • Head distinctly broader than long (CI 1.10-1.19); propodeal spines longer (SPI 0.10- 0.26); tricolored: orange-red, yellow and black . . . . . Crematogaster tricolor
  • Head not much broader than long (CI 1.01-1.13); propodeal spines shorter (SPI < 0.16); uniformly colored or bicolored . . . . . 12

12

return to couplet #11

  • Mesonotum often with posterolateral denticles (Fig. 5C); in lateral view distinctly set off from propodeum (Fig. 5C); eyes large (OI 0.22-0.26); propodeal spines longer (SPI 0.10-0.16); erect pilosity on promesonotum often sparse ( < 8 long erect setae) (as e.g. Figs 5C) . . . . . Crematogaster degeeri
  • Mesonotum variable, but more often without posterolateral denticles, and thus in lateral view not as distinctly set off from promesonotum (Fig. 5D); erect pilosity usually more abundant ( > 8 long erect setae) (as in Fig. 5D, E); propodeal spines shorter (SPI < 0.12) . . . . . 13
Figure 5. A. Pronotum with sharp lateral margins C. malahelo. B. Pronotum lacking sharp lateral margin C. alafara. C. Mesonotum with posterolateral denticles C. degeeri. D. Mesonotum without distinct posterolateral denticles C. ramamy. E. Propodeum with distinct short dorsal face and transverse impression, sculpture carinulate C. ramamy. F. Propodeum lacking distinct dorsal face and transverse impression, sculpture rugulose C. dentata.

13

return to couplet #12

  • Propodeum with a distinct short dorsal face, and with a transverse impression (Fig. 5E); sculpture on pronotum carinulate or reticulate (Fig. 5E); petiole oval, fairly slender; (PTWI 0.95-1.14); propodeal spines longer (SPI 0.07-0.12) . . . . . Crematogaster ramamy
Crematogaster ramamy casent0317764 p 1 high.jpg
  • Propodeum usually without a distinct dorsal face, never with transverse impression (Fig. 5F); sculpture on propodeum rugulose or aciculate (Fig. 5F); petiole variable, but often wider (PTWI 0.95-1.31); propodeal spines usually shorter (SPI 0.01-0.10) . . . . . Crematogaster dentata (in part - also #5) (in part - also #7)
Crematogaster sewellei dentata casent0059574 profile 1.jpg