Tetramorium dalek

The new species is found in the lowland and montane rainforests of eastern Madagascar from the southernmost localities Sandranantitra, Betampona, and Zahamena, north to Anjanaharibe-Sud. In addition, T. dalek has an elevational range from 20 to 1280 m, and seems to live in leaf litter.

Identification
A member of the Tetramorium naganum-species group. Hita Garcia and Fisher (2014) - Tetramorium dalek is easily distinguishable by the following combination of characters: waist segments without long standing hairs, instead with short, appressed to subdecumbent pubescence only, sometimes with one or two short erect to suberect hairs; propodeal spines moderately long to long (PSLI 25–27); first gastral tergite with short, relatively dense, appressed to subdecumbent pubescence and without any standing hairs at all.

Tetramorium dalek is easily distinguishable within the T. naganum species group since it is the only species without long, standing hairs on the waist segments and the first gastral tergite, and in addition, it also has generally shorter propodeal spines (PSLI 25–27) than the other four species (PSLI 27–37). But it is possible to mistake T. dalek with species from other groups. Its general habitus and in particular its lack of standing pilosity on the first gastral tergite could lead to misplacement in the T. schaufussii complex of the T. schaufussii species group or the T. ibycterum complex in the T. ranarum group. Indeed, a misidentification with one species from the latter complex is likely. Tetramorium ibycterum superficially shares many characters with T. dalek, and even most morphometric ranges. However, T. ibycterum has very well developed antennal scrobes with clearly defined margins all around, whereas T. dalek has weaker antennal scrobes without clearly defined margins all around. In addition, T. dalek differs from the species of the Tetramorium schaufussii complex in having a broader head (CI 95–97) and higher and stouter mesosoma (LMI 42–46). Consequently, despite morphological similarities to other species groups, we consider T. dalek best placed in the T. naganum group

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  dalek. Tetramorium dalek Hita Garcia & Fisher, 2014: 15, figs. 1A, 6, 61 (w.) MADAGASCAR.

Worker
(N=12). HL 0.47–0.56 (0.51); HW 0.45–0.54 (0.49); SL 0.31–0.35 (0.33); EL 0.11–0.13 (0.12); PH 0.23–0.30 (0.26); PW 0.34–0.39 (0.36); WL 0.54–0.68 (0.61); PSL 0.12–0.15 (0.13); PTL 0.12–0.14 (0.12); PTH 0.19–0.22 (0.20); PTW 0.13–0.17 (0.15); PPL 0.13–0.16 (0.15); PPH 0.19–0.21 (0.19); PPW 0.18–0.22 (0.20); CI 95–97 (96); SI 63–70 (67); OI 23–24 (24); DMI 54–63 (59); LMI 42–46 (43); PSLI 25–27 (26); PeNI 38–46 (42); LPeI 55–68 (61); DPeI 108–139 (123); PpNI 53–59 (56); LPpI 70–80 (76); DPpI 131–147 (139); PPI 126–138 (133).

Head longer than wide (CI 95–97); posterior head margin weakly concave. Anterior clypeal margin with distinct median impression. Frontal carinae strongly developed, diverging posteriorly, and usually approaching or ending at posterior head margin; antennal scrobe present, but weak, shallow, and without defined posterior or ventral margins. Antennal scapes short, not reaching posterior head margin (SI 63–70). Eyes of moderate size (OI 23–24). Mesosomal outline in profile flat to very weakly convex, relatively high (LMI 42–46), and moderately to strongly marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent. Propodeal spines elongate-triangular to spinose, moderately long to long, and acute (PSLI 25–27); propodeal lobes short, triangular, and blunt or acute, always much shorter than propodeal spines. Petiolar node in profile high, rounded nodiform to weakly rectangular nodiform, with moderately rounded antero- and posterodorsal margins, around 1.5 to 1.8 times higher than long (LPeI 55–68), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about the same height and equally marginate (very rarely posterodorsal margin more rounded and lower than anterodorsal margin), petiolar dorsum flat to very weakly convex; node in dorsal view around 1.1 to 1.4 times wider than long (DPeI 108–139), in dorsal view pronotum between 2.2 to 2.6 times wider than petiolar node (PeNI 38–46). Postpetiole in profile globular, approximately 1.2 to 1.4 times higher than long (LPpI 70–80); in dorsal view around 1.3 to 1.5 times wider than long (DPpI 131–147), pronotum between 1.7 to 1.9 times wider than postpetiole (PpNI 53–59). Postpetiole in profile appearing slightly more voluminous than petiolar node, postpetiole in dorsal view around 1.3 to 1.4 times wider than petiolar node (PPI 126–138). Mandibles distinctly striate; clypeus longitudinally rugose/rugulose, with three to five rugae/rugulae, median ruga always well developed and distinct, lateral rugae/rugulae sometimes weaker and interrupted; cephalic dorsum between frontal carinae with seven to ten longitudinal rugae, rugae running from posterior clypeal margin to posterior head margin, often interrupted or with cross-meshes, especially posteriorly; scrobal area mostly unsculptured; lateral head longitudinally rugose to reticulate-rugose. Ground sculpture on head absent to weakly punctate. Mesosoma laterally and dorsally mostly irregularly longitudinally rugose. Forecoxae unsculptured, smooth and shining. Ground sculpture on mesosoma weak to absent. Waist segments and gaster completely unsculptured, smooth and shining. Head and mesosoma with numerous, moderately long and fine standing hairs; waist segments and first gastral tergite with short, comparatively dense, appressed to subdecumbent pubescence, sometimes several of these short hairs suberect to erect. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae usually with decumbent to suberect hairs. Head, mesosoma, waist segments, and gaster generally orange-brown to chestnut brown, mandibles, antennae, and legs always lighter, usually yellowish brown.

Type Material
Holotype, MADAGASCAR, Toamasina, Montagne d’Anjanaharibe, 19.5 km 27° NNE Ambinanitelo, 15.1783°S, 49.635°E, 1100 m, montane rainforest, sifted litter (leaf mold, rotten wood), collection code BLF08150, 12.–16.III.2003 (B.L. Fisher et al.) (: CASENT0038402). Paratypes, 17 pinned workers with same data as holotype (: CASENT0038394; CAS: CASENT0038369; CASENT0038372; CASENT0038376; CASENT0038390; CASENT0038408; CASENT0038413; CASENT0038416; CASENT0038425; CASENT0038429; CASENT0038443; CASENT0038445; CASENT0038450; CASENT0038456; CASENT0038465; : CASENT0038397; CASENT0038424); and seven workers from MADAGASCAR, Toamasina, Montagne d’Anjanaharibe, 18.0 km 21° NNE Ambinanitelo, 15.1883°S, 49.615°E, 470 m, rainforest, sifted litter (leaf mold, rotten wood), collection code BLF08802, 8.–12.III.2003 (B.L. Fisher et al.) (CAS: CASENT0037833; CASENT0037869; CASENT0037903; CASENT0037909; CASENT0037916; CASENT0037933; CASENT0037936).

Etymology
The name of the new species is taken from the popular British TV show “Dr. Who” and refers to a fictional, extra-terrestrial race of evil mutants. During different stages of the revision we considered placing the material listed here as T. dalek in at least three to four different groups, which caused a significant amount of nuisance, especially to the first author. Naming this species after an evil, extra-terrestrial, and often annoying race was a logical consequence. The species epithet is an arbitrary combination of letters, thus invariant.

References based on Global Ant Biodiversity Informatics

 * Hita Garcia F, and B. L. Fisher. 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.