Key to the workers of the Crematogaster (Decacrema) -group, Malagasy region

1. Petiole dorsally with postero-lateral tubercles, each bearing a single, stiff and long erect seta (Fig. 21 a); postpetiole distinctly bilobed and broadly medially impressed, with a pair of dorso-posterior stiff, long erect setae (Fig. 21 b); abdominal tergites 4–7 usually with scattered erect pilosity; mandibles with 4 teeth .................................................. 2

- Petiole dorsally lacking postero-lateral tubercle, setae commonly absent, if present (rare) then short and feeble; postpetiole variable, usually without erect setae; erect pilosity absent from abdominal tergites 4–7; mandibles with 4–5 teeth............................................................................................................................................................................... 3

2(1) Lateral portions of promesonotum raised with respect to median portion, and with postero-lateral carinate denticles and lateral carinae bordering metanotal groove, in lateral view promesonotum appearing dorsally flat (Fig. 22, or as in Fig. 37 b); widespread in western and southern dry and spiny forests .......................................................... C. grevei

- Lateral portions of promesonotum not raised with respect to median portion, postero-laterally rounded or angular and metanotal groove without lateral carinae, in lateral view promesonotum forming a more or less convex outline (Fig. 23, or as in Fig. 36 b); rare, montane forests of southern central Madagascar ...................................... C. malala

3(1) Head and promesonotal sculpture well pronounced, deeply costulate (Fig. 11 and 47 a) or areolate (Fig. 9 and 48 a) .. .......................................................................................................C. hova- complex (morphotypes 4, 5, and part of 3)

- Head and promesonotal sculpture less developed, from reduced-aciculate (Fig. 8, or e.g. 44a) to reticulate (Fig. 10), reticulate-areolate (e.g. Fig. 46 a) to weakly costulate .................................................................................................. 4

4(3) Face lacking erect setae except a single pair near frontal carinae; subpetiolar process developed as broad protuberance (Fig. 25 and 38 b); small to medium size (HW 0.86–1.04, WL 0.80–1.05); propodeal spines small to medium size (SPI 0.15–0.20); sculpture on head and promesonotum always reduced-aciculate; northern, northwestern Madagascar and Ambohitantely forest. .......................................................................................................... C. nosibeensis

- Face with additional erect setae (careful, could be abraded) other than those close to frontal carinae; subpetiolar process variable; size highly variable, small to very large (HW 0.74–1.31, WL 0.78–1.34); propodeal spines variable (SPI 0.17–0.40), but commonly SPI> 0.20; sculpture variable. .................................................................................. 5

5(4) Subpetiolar process developed as acute, long tooth (Fig. 24 and 39 b); promesonotal suture usually complete; medium to large size (HW 0.89–1.14, WL 0.91–1.12); propodeal spines small to medium size (SPI 0.17–0.21); head and promesonotal sculpture always reduced-aciculate; rare, known only from montane forests in R. S. Manongarivo ............................................................................................................................................................................. C. sisa

- Subpetiolar process variable, moderately articulated as angular dent (Fig. 26, 41 b, 49b, 50b, 52b and 53b), close to absent (Fig. 27 and 51 b), or rarely as a broad protuberance (Fig. 40 b); promesonotal suture often incomplete, if complete, then large to very large species (HW 1.09–1.21, WL 1.18–1.32); otherwise size highly variable; propodeal spines usually with SPI> 0.20; sculpture variable. ...................................................................................................... 6

6(5) Mesonotum postero-laterally distinctly angular to tuberculate (Fig. 28 b and 30b, or as in 32b–35b); large to very large species (HW 1.09–1.31, WL 1.18–1.34); head usually reduced-aciculate, sometimes reticulate to feebly costulate; uncommon, central, eastern central and southeastern Madagascar. ................................................................... 7

- Mesonotum postero-laterally rounded or slightly tuberculate (Fig. 29, and as in 44b–48b), rarely angular; body size small to large (HW 0.74–1.19, WL 0.78–1.22); head sculpture variable, aciculate, reticulate or reticulate-areolate, if head sculpture reduced and aciculate, then usually at least promesonotal sculpture more developed; widespread throughout humid forests in Madagascar ......................................C. hova- complex (morphotypes 1, 2, and part of 3)

7(6) Mesonotum raised with respect to pronotum and medially at least slightly tuberculate (Fig. 30 a); promesonotal suture usually complete (Fig. 31 a); head and promesonotal sculpture always aciculate. .............................. C. mahery

- Mesonotum usually not raised with respect to pronotum nor medially tuberculate (Fig. 28 a), promesonotal suture usually incomplete (Fig. 31 b) and only laterally impressed; head sculpture and promesonotal sculpture either aciculate or reticulate to weakly costulate............................................................................................................ C. sabatra *