Key to Tetramorium cognatum species complex

This worker key is based on: Hita Garcia, F. & Fisher, B.L. 2014. The hyper-diverse ant genus Tetramorium Mayr (Hymenoptera, Formicidae) in the Malagasy region ‑ taxonomic revision of the T. naganum, T. plesiarum, T. schaufussii, and T. severini species groups. ZooKeys 413, 1–170 (doi: 10.3897/zookeys.413.7172).

You may also be interested in:

• Tetramorium schaufussii species group (species list, diagnosis, distribution, etc.)
• Key to Malagasy Tetramorium species groups
• Tetramorium

1

• Mesosoma without any long, standing hairs (Fig. 21A) [Madagascar] . . . . . Tetramorium freya

• Mesosoma always with few to numerous pairs of standing hairs (Fig. 21B, C) . . . . . 2

Hita Garcia and Fisher, 2014. Figure 21.

2

return to couplet #1

• Petiolar node strongly squamiform, in profile 2.8 to 3.0 times higher than long (LPeI 33–36) and in dorsal view around 2.3 to 2.4 times wider than long (DPeI 228–238) (Fig. 22A) [Madagascar] . . . . . Tetramorium camelliae

• Petiolar node never strongly squamiform as above, in profile 1.6 to 2.7 (usually 1.6 to 2.2) times higher than long (LPeI 37–62) and in dorsal view between 1.1 to 1.7 times wider than long DPeI 111–171) (Fig. 22B, C, D) . . . . . 3

Hita Garcia and Fisher, 2014. Figure 22.

3

return to couplet #2

• Eyes relatively small (OI 19–20) (Fig. 23A) [Madagascar] . . . . . Tetramorium gladius

• Eyes always much larger than above (OI 24–31) (Fig. 23B, C, D) . . . . . 4

Hita Garcia and Fisher, 2014. Figure 23.

4

return to couplet #3

• Larger species (HW 0.58–0.81; WL 0.85–1.07); frontal carinae moderately well to strongly developed, noticeably raised, and usually approaching or ending at posterior head margin (Fig. 24A, B) . . . . . 5

• Smaller species (HW 0.43–0.55; WL 0.56–0.81); frontal carinae usually weakly developed, faintly raised, and mostly ending or fading into surrounding sculpture halfway between posterior eye margin and posterior head margin (Fig. 24C, D) . . . . . 7

Hita Garcia and Fisher, 2014. Figure 24.

5

return to couplet #4

• Usually significantly larger species (HW 0.65–0.81; WL 0.92–1.07); mesosoma usually with five or six pairs of long, standing hairs on pronotum and mesonotum (Fig. 25A) [Madagascar] . . . . . Tetramorium proximum

• Usually smaller species (HW 0.58–0.70; WL 0.76–0.94); mesosoma always with only two pairs of long, standing hairs, one pair on anterior pronotum and one on anterior mesonotum (Fig. 25B, C) . . . . . 6

Hita Garcia and Fisher, 2014. Figure 25.

6

return to couplet #5

• Antennal scapes shorter (SI 66–70); petiolar node higher, around 1.8 to 2.2 times higher than long (LPeI 45–54); postpetiole in dorsal view around 1.5 to 1.7 times broader than petiolar node (PPI 148–167) (Fig. 26A, B) [Madagascar] . . . . . Tetramorium tenuinode

• Antennal scapes longer (SI 74–76); petiolar node lower, around 1.6 to 1.7 times higher than long (LPeI 58–60) postpetiole in dorsal view only around 1.3 to 1.4 times broader than petiolar node (PPI 133–141) (Fig. 26C) [Madagascar] . . . . . Tetramorium myrmidon

Hita Garcia and Fisher, 2014. Figure 26.

7

return to couplet #4

• Smaller species (HW 0.43–0.49; WL 0.56–0.67); propodeal spines moderately long to long, elongate-triangular to spinose (PSLI 22–26); petiolar node thinly cuneiform and moderately squamiform, in profile around 2.3 to 2.7 times higher than long (LPeI 37–43), in dorsal view around 1.6 to 1.7 times wider than long (DPeI 156–171); colouration always uniformly whitish yellow to light yellowish brown (Fig. 27A) [Madagascar] . . . . . Tetramorium rumo

• Larger species (HW 0.48–0.55; WL 0.65–0.81); propodeal spines short to moderately long, triangular to elongate-triangular (PSLI 12–22); petiolar node high nodiform, in profile around 1.8 to 2.2 times higher than long (LPeI 46–55), in dorsal view 1.3 to 1.6 times wider than long (DPeI 129–161); colouration variable, but rarely yellowish as above (Fig. 27B, C) . . . . . 8

Hita Garcia and Fisher, 2014. Figure 27.

8

return to couplet #7

• Antennal scapes shorter (SI 61–67); propodeal spines reduced and very short (PSLI 12–16), propodeal spines and lobes often of same length or spines even shorter, never strongly directed towards each other; petiolar node in dorsal view around 1.3 to 1.4 times wider than long (DPeI 129–142) (Fig. 28A, B) [Madagascar] . . . . . Tetramorium cognatum

• Antennal scapes longer (SI 68–72); propodeal spines short to moderately long (PSLI 18–22), spines either much longer than lobes or only weakly so and spines and lobes strongly inclined towards each other; petiolar node in dorsal view around 1.5 to 1.6 times wider than long (DPeI 146–161) (Fig. 28C, D) . . . . . 9

Hita Garcia and Fisher, 2014. Figure 28.

9

return to couplet #8

• Eyes smaller (OI 25–27); propodeal lobes always only weakly shorter than propodeal spines, and spines and lobes strongly inclined towards each other; dorsal mesosoma with six or more pairs of long, standing hairs on pronotum and mesonotum, and propodeum usually with one or two pairs anteriorly (Fig. 29A) [Madagascar] . . . . . Tetramorium aspis

• Eyes larger (OI 29–30); propodeal lobes short and triangular, always much shorter than propodeal spines, and spines and lobes never strongly inclined towards each other; dorsal mesosoma with two to four pairs of long, standing hairs on pronotum and mesonotum, standing hairs absent from propodeum (Fig. 29B) [Comoros] . . . . . Tetramorium karthala

Hita Garcia and Fisher, 2014. Figure 29.