Tetramorium gollum Hita Garcia & Fisher

Hita Garcia, Francisco & Fisher, Brian 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, pp. 1-170 : 29-31

Tetramorium gollum Hita Garcia & Fisher sp. n. Figs 10D, 11A, 16, 62

Type material.

Holotype, pinned worker, MADAGASCAR, Fianarantsoa, Forêt d’Analalava, 29.6 km 280° W, Ranohira, 22.59167°S, 45.12833°E, 700 m, tropical dry forest, pitfall trap, collection code BLF07381, 1.-5.II.2003 (CAS: CASENT0074849). Paratypes, two pinned workers with same data as holotype (CAS: CASENT0074839, CASENT0074974).

Diagnosis.

The strongly developed sculpture on the basal half of the first gastral tergite and the extremely swollen gaster clearly distinguish Tetramorium gollum from the other species in the group.

Worker measurements

(N=3). HL 0.76-0.90 (0.81); HW 0.74-0.90 (0.80); SL 0.47-0.59 (0.52); EL 0.15-0.18 (0.16); PH 0.48-0.52 (0.50); PW 0.54-0.66 (0.59); WL 0.85-1.03 (0.93); PSL 0.23-0.26 (0.25); PTL 0.20-0.25 (0.23); PTH 0.35-0.42 (0.38); PTW 0.27-0.37 (0.31); PPL 0.24-0.27 (0.25); PPH 0.37-0.43 (0.40); PPW 0.40-0.50 (0.45); CI 97-100 (98); SI 64-66 (65); OI 19-20 (20); DMI 62-64 (63); LMI 50-56 (54); PSLI 29-31 (30); PeNI 50-56 (53); LPeI 57-61 (59); DPeI 130-148 (138); PpNI 75-79 (76); LPpI 63-65 (64); DPpI 167-185 (176); PPI 135-148 (143).

Worker description.

Head weakly longer than wide to as long as wide (CI 97-100); posterior head margin weakly concave. Anterior clypeal margin with distinct median impression. Frontal carinae strongly developed, curving down shortly before posterior head margin, forming dorsal margin of very well-developed antennal scrobes; scrobes moderately shallow; posterior and ventral margins not fully defined, merging with very strong cephalic sculpture. Antennal scapes short, not reaching posterior head margin (SI 64-66). Eyes relatively small (OI 19-20). Mesosomal outline in profile conspicuously convex, rounded, and very high (LMI 50-56), moderately to strongly marginate from lateral to dorsal mesosoma; promesonotal suture and metanotal groove absent. Propodeal spines long (PSLI 29-31), elongate-triangular to spinose, and acute; propodeal lobes short, triangular to elongate-triangular, and acute. Petiolar node in profile high, rectangular nodiform with well-defined antero- and posterodorsal margins, between 1.6 to 1.8 times higher than long (LPeI 57-61), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about the same height, petiolar dorsum flat to weakly convex; node in dorsal view around 1.3 to 1.5 times wider than long (DPeI 130-148), in dorsal view pronotum between 1.8 to 2.0 times wider than petiolar node (PeNI 50-56). Postpetiole in profile anteroposteriorly compressed, approximately 1.5 to 1.6 times higher than long (LPpI 63-65); in dorsal view around 1.7 to 1.9 times wider than long (DPpI 167-185), pronotum only around 1.3 times wider than postpetiole (PpNI 75-79). Postpetiole in profile appearing approximately as voluminous as petiolar node but relatively thinner, postpetiole in dorsal view approximately 1.3 to 1.5 times wider than petiolar node (PPI 135-148). Gaster extremely enlarged and swollen. Mandibles unsculptured, smooth, and shining; clypeus longitudinally rugose, with five to six distinct rugae, median ruga better developed than remainder, rugae without cross-meshes; sculpture on cephalic dorsum between frontal carinae variable: either mainly longitudinally rugose with higher proportion of reticulate-rugose areas towards posterior head margin, or irregularly reticulate-rugose with a higher proportion of longitudinally rugose sculpture restricted anteriorly close to posterior clypeal margin; scrobal area partly unsculptured; lateral head longitudinally rugose to reticulate-rugose. Mesosoma laterally reticulate-rugose to irregularly longitudinally rugose with a few shining areas on mesopleuron and propodeum, dorsally reticulate-rugose to irregularly longitudinally rugose. Forecoxae unsculptured, smooth, and shining. Petiolar node laterally with weak, longitudinally rugose sculpture mostly restricted towards dorsum, dorsum of node mostly unsculptured, smooth, and shiny; sculpture on postpetiole better developed, laterally and dorsally reticulate-rugose. Basal half of first gastral tergite and most of first sternite with very conspicuous and strongly developed reticulate-rugose sculpture superimposed on a reticulate-punctate ground sculpture; remainder of gaster unsculptured, smooth, and shining. Ground sculpture on head, mesosoma, and waist segments weak to moderate, except procoxae with weak but distinct rugulose ground sculpture. Whole body with abundant, long, and fine standing hairs; first gastral tergite with a mix of more abundant, long, erect hairs and much scarcer, shorter, decumbent to subdecumbent hairs. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with decumbent to suberect hairs. Head, mesosoma, and waist segments light to dark brown, mandibles, antennae, and legs light brown to yellow, and gaster much darker brown than remainder of body.

Etymology.

The new species is named after the fictional character “Gollum” from J.R.R. Tolkien’s novels "The Hobbit" and "The Lord of the Rings". The species epithet is an arbitrary combination of letters, thus invariable.

Distribution and ecology.

The new species is only known from the type locality, the Forêt d’Analalava, which is a tropical dry forest located at an elevation of 700 m (Fig. 62). The biology of the species is unknown, but foraging might be undertaken on the ground since the only three known specimens were collected from a pitfall trap. Indicated by this lack of material, Tetramorium gollum probably is one of the more rarely encountered Tetramorium species in Madagascar.

Discussion.

Tetramorium gollum is a very conspicuous species within the Tetramorium plesiarum group and the whole Malagasy Tetramorium fauna. The extremely swollen gaster with strongly developed sculpture on the basal half of the tergite is easily recognisable within the species group. The only other Malagasy species with such conspicuous sculpture clearly extending to half of the tergite or more are Tetramorium jedi in the Tetramorium tortuosum group and Tetramorium sericeiventre in the Tetramorium sericeiventre group. The latter has 12 antennal segments (vs. 11 in Tetramorium gollum ) and Tetramorium jedi has, among other characters, a very differently shaped petiolar node (longer than broad in Tetramorium jedi vs. broader than long in Tetramorium gollum ). Beyond sculpture and the enlarged gaster, Tetramorium gollum is morphologically very similar to Tetramorium bressleri , for example the petiolar node shape is identical in both suggesting a close relationship. However, they both also differ in the shape of the postpetiole, which is much higher and broader in Tetramorium gollum (LPpI 63-65; DPpI 167-185) than in Tetramorium bressleri (LPpI 59-63; DPpI 150-158).