Tetramorium adamsi

Hita Garcia, F. & B. L. Fisher, 2012, The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region - taxonomic revision of the T. kelleri and T. tortuosum species groups., Zootaxa 3592, pp. 1-85 : 66-67

Tetramorium adamsi can be straightforwardly recognised within the T. smaug species complex since it is the only species in which the posterodorsal margin of the petiolar node is situated higher than the anterodorsal margin.

Description

HL 0.94-1.06 (1.01); HW 0.89-1.03 (0.96); SL 0.69-0.82 (0.76); EL 0.17-0.21 (0.19); PH 0.43-0.55 (0.50); PW 0.63-0.78 (0.72); WL 1.13-1.45 (1.30); PSL 0.34-0.51 (0.44); PTL 0.31-0.39 (0.36); PTH 0.34-0.42 (0.38); PTW 0.25-0.31 (0.28); PPL 0.29-0.32 (0.31); PPH 0.34-0.42 (0.38); PPW 0.34-0.39 (0.36); CI 93-97 (95); SI 73-84 (79); OI 18-22 (20); DMI 51-59 (56); LMI 34-40 (38); PSLI 36-50 (43); PeNI 36-41 (39); LPeI 88-97 (93); DPeI 76-84 (79); PpNI 47-54 (50); LPpI 75-86 (81); DPpI 113-126 (117); PPI 116-138 (127) (18 measured).

Head longer than wide (CI 93-97); posterior head margin concave. Anterior clypeal margin medially impressed. Frontal carinae strongly developed, diverging posteriorly, and ending at corners of posterior head margin. Antennal scrobes weakly developed, shallow, and narrow, without defined posterior and ventral margins. Antennal scapes short to moderate in length, not reaching posterior head margin (SI 73-84). Eyes short to moderately sized (OI 18-22). Mesosomal outline in profile flat to weakly convex, moderately marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent; mesosoma comparatively stout and high (LMI 34-40). Propodeal spines very long to extremely long, spinose and acute (PSLI 36-50); propodeal lobes well-developed, triangular to elongate-triangular, and usually acute. Petiolar node in profile rectangular nodiform, approximately 1.0 to 1.1 times higher than long (LPeI 81-88), anterior and posterior faces approximately parallel, posterodorsal margin situated higher than anterodorsal margin, dorsum convex; node in dorsal view approximately 1.2 to 1.3 times longer than wide (DPeI 76-84). Postpetiole in profile subglobular, approximately 1.2 to 1.3 times higher than long (LPpI 75-86); in dorsal view around 1.1 to 1.3 times wider than long (DPpI 113-126). Postpetiole in profile generally appearing less voluminous than petiolar node, in dorsal view between 1.1 to 1.4 time s wider than petiolar node (PPI 116-138). Mandibles striate; clypeus longitudinally rugose/rugulose, with four to eight rugae/rugulae, median ruga usually present and distinct, but rarely more conspicuous than other rugae/rugulae; cephalic dorsum between frontal carinae with eight to 13 longitudinal rugae, most rugae running unbroken from posterior head margin to anterior clypeus, few rugae interrupted and with cross-meshes; lateral and ventral head mostly reticulate-rugose. Mesosoma laterally and dorsally distinctly longitudinally rugose. Forecoxae with well-developed and conspicuous longitudinal rugae. Waist segments strongly rugose. Gaster mostly unsculptured, smooth, and shining, several specimens from higher elevations with dist inct costulae on the basal half of first gastral tergite. Ground sculpture generally faint to absent everywhere on body, better developed at higher elevations, but still weak. All dorsal surfaces with abundant, long, and fine st anding hairs. Anterior edges of antennal scapes with suberect to erect hairs. Body generally uniformly dark brown to black in colour, sometimes appendages of slightly lighter colour.

Notes

The new species is currently only known from Manongarivo and Bemanevika, where it was collected from montane forest leaf litter at elevations from 1175 to 1860 m. Almost all of the material was sampled in Manongarivo while just one specimen from Bemanevika was available.

Tetramorium adamsi shows a remarkable variation in Manongarivo. The examined material was collected from three sub-localities located at different altitudes separated by few kilometres from each other. The lowest was situated at 1175 m, the middle at 1580, and the highest at 1860 m. The specimens from 1175 m had longer antennal scapes (SI 81-84), longer propodeal spines (PSLI 47-50), and a narrower postpetiole in relation to the petiolar node (PPI 116-125) than specimens from the higher elevations (SI 73-78; PSLI 36-41; PPI 129-138). These differences were fairly constant between the series, and we have considered separating the material into two species. However, the only arguments for separation are morphometric divergences, and apart from this there is a great amount of morphological similarity. For these reasons, we have decided against a split. In addition, we found that on half of the workers from the highest elevation at 1860 m, the basal half of the first gastral tergite is distinctly costulate while it is unsculptured and smooth in the remaining specimens. Sculpture on the first gastral tergite is generally of high diagnostic importance in the T. tortuosum group, and could have been a reason to split the T. adamsi material. Nevertheless, no other character could separate the sculptured specimens from those collected at the two higher sub-localities. This has convinced us to keep all the material as one variable, but well-defined species.

Within the T. smaug species complex, it is fairly easy to discriminate T. adamsi from the other species on the basis of the petiolar node shape. The node has the posterodorsal margin situated higher than the anterodorsal margin in T. adamsi, whereas both margins are at about the same height in the rest of the complex.

Etymology

The name of the new species is a patronym in honour of the British writer Douglas Adams best known for "The Hitchhiker's Guide to the Galaxy" series. (1952-2001.

Material examined

MADAGASCAR: Antsiranana, R.S. Manongarivo, 14.5 km 220° SW Antanambao, 13.99833 S, 48.42833 E, 1175 m, montane rainforest, 19.-25.X.1998 (B.L. Fisher); Mahajanga, Bemanevika, Souspref. de Bealanana, forest, 20. X. 1975 (A. Peyrieras); Antsiranana, R.S. Manongarivo 17.3 km 218° SW Antanambao, 14.02167 S, 48.41833 E, 1580 m, montane rainforest, 27.X.1998 (B.L. Fisher); Antsiranana, R.S. Manongarivo, 20.4 km 219° SW Antanambao, 14.04667 S, 48.40167 E, 1860 m, montane rainforest, 3.XI.1998 (B.L. Fisher); Mahajanga, Bemanevika, Soupref. de Bealanana, 20.X.1975 (A. Peyrieras).