Tetramorium boltoni

Tetramorium boltoni is a widely distributed and very common rain forest species.

Identification
Tetramorium boltoni can be best distinguished from other members of the species complex by the following character combination: SI 71 - 78; propodeal spines moderately sized to long (PSLI 23 - 29), elongate-triangular with a broad base to spinose; head and mesosoma strongly longitudinally rugose, ground sculpturation generally reduced, smooth and shiny; standing hairs present on first gastral tergite; coloration uniformly very dark brown to black.

A member of the Afrotropical weitzeckeri species complex, which is part of the weitzeckeri species group.

Key to weitzeckeri-group species.

Distribution
Nigeria to Western Kenya and from Sudan to Angola. Known from Angola, Cameroon, Central African Republic, Democratic Republic of Congo, Equatorial Guinea, Gabon, Kenya, Nigeria, Uganda and Sudan This taxon was described from Kenya.

Habitat
Rainforest

Nomenclature

 *  boltoni. Tetramorium boltoni Hita Garcia, Fischer & Peters, 2010b: 66, figs. 10A, 11B, 16B, 17B, 18B, 76-78 (w.) KENYA.

This species was previously identified as Tetramorium weitzeckeri but it is clearly distinctive based on its morphology, habitat preference, and biogeography. Tetramorium boltoni is generally significantly smaller in size (HW 0.644 - 0.744, SL 0.467 - 0.539, PW 0.489 - 0.561, WL 0.778 - 0.911) compared to T. weitzeckeri (HW 0.772 - 0.933, SL 0.789 - 0.944, PW 0.578 - 0.711, WL 0.911 - 1.206). Additionally, several body parts, such as the antennal scapes and the propodeal spines, are distinctly less strongly developed in T. boltoni (SI 71 - 78, PSLI 23 -29) than in T. weitzeckeri (SI 77 - 83, PSLI 32 - 45). Furthermore, T. boltoni is a strict forest species inhabiting the leaf litter stratum of Equatorial rain forests while T. weitzeckeri prefers open habitats in Eastern or Southern Africa. The differentiation of T. boltoni from Tetramorium snellingi is easier since T. snellingi is smaller, distinctly bicoloured and possesses smaller propodeal spines (PSLI 17 - 22). In addition, T. boltoni cannot be confused with the morphologically close Tetramorium renae since this species is usually bicoloured, with the gaster of lighter colour than the mesosoma, and shows a high grade of reduction in mesosomal sculpturation. Also Tetramorium guineense with its conspicuous, strong and dense reticulate-punctate ground sculpture on the head and the longer propodeal spines (PSLI 28 - 43) can be simply separated from T. boltoni. The remaining species of the weitzeckeri complex differ from T. boltoni by their absence of standing hairs on the first gastral tergite.

Worker
HL 0.678 - 0.761 (0.717); HW 0.644 - 0.744 (0.686); SL 0.467 - 0.539 (0.513); EL 0.144 - 0.167 (0.155); PW 0.489 - 0.561 (0.523); WL 0.778 - 0.956 (0.843); PSL 0.167 - 0.217 (0.186); PTL 0.100 - 0.128 (0.112); PTH 0.289 - 0.339 (0.313); PTW 0.256 - 0.306 (0.275); PPL 0.144 - 0.200 (0.176); PPH 0.267 - 0.333 (0.298); PPW 0.289 - 0.356 (0.320); CI 92 - 100 (96); SI 71 - 79 (75); OI 21 - 24 (22); PSLI 23 - 29 (26); PeNI 48 - 60 (53); LPeI 31 - 40 (36); DPeI 226 - 267 (245); PpNI 55 - 65 (61); LPpI 52 - 67 (59); DPpI 167 - 200 (182); PPI 105 - 125 (117) (47 measured).

Head slightly longer than wide, sometimes as long as wide (CI 92 - 100). Anterior clypeal margin distinctly medially impressed. Frontal carinae strongly developed, becoming weaker behind level of eye and ending shortly before posterior margin of head. Antennal scrobe narrow, shallow, and without defined ventral margin, ending before posterior margin of head. Antennal scape of medium length (SI 71 - 79). Eyes relatively small to moderate (OI 21 -24), with 7 to 9 ommatidia in longest row. Metanotal groove impressed. Propodeal spines long (PSLI 23 - 29), elongate-triangular to spinose with broad base and acute apex. Propodeal lobes small, elongate-triangular and acute. Node of petiole squamiform, in dorsal view more than 2 times wider than long (DPeI 226 - 260) and in profile 2.5 to 3.2 times higher than long (LPeI 32 - 40). Postpetiole in dorsal view distinctly wider than long (DPpI 167 - 200) and much more voluminous than petiole. In lateral view postpetiole weakly to moderately squamiform and thicker compared to petiole, only slightly antero-posteriorly compressed, between 1.5 to 1.9 times higher than long (LPpI 52 - 67). Mandibles distinctly longitudinally striate. Clypeus usually with 3 to 5 longitudinal rugae, median ruga always strongly developed and unbroken, while lateral rugae variable. Head longitudinally rugose with widely spaced rugae, dorsum usually with 7 to 10 longitudinal rugae between frontal carinae, almost all running unbroken to posterior margin of head. Spaces between rugae with very weak, nearly effaced ground sculpture or completely unsculptured, generally shiny. Scrobal area with reduced punctate ground sculpture or unsculptured. Mesosoma dorsally and laterally with coarse, mostly longitudinal, widely spaced rugulation. Spaces between rugae and propodeal declivity unsculptured, smooth and shiny. Petiole, postpetiole and gaster completely unsculptured, smooth and shiny. All dorsal surfaces of head, mesosoma, both waist segments and gaster with abundant, long, fine, and simple suberect to erect hairs. Fine pubescence on tibiae appressed, on antennal scapes appressed to decumbent. Head, mesosoma, petiole, postpetiole, and gaster uniformly very dark brown to black, appendages often of lighter colour.

Type Material
Holotype worker, KENYA, Western Province, Kakamega Forest, Salazar, Transect 6, 00° 19' 36 N, 34° 52' 14.6 E, 1650m, 21.VI.2007, Kakamega 2007 survey, primary rain forest, pitfall trap, leg. M. Peters ( - ZFMK_HYM_2009_6145). Paratypes, 40 workers with same data as holotype (: 8 workers ZFMK_HYM_2009_6163, ZFMK_HYM_2009_6164, ZFMK_HYM_2009_6165, ZFMK_HYM_2009_6166, ZFMK_HYM_2009_6167; : 6 workers ZFMK_HYM_2009_6248, ZFMK_HYM_2009_6249, ZFMK_HYM_2009_6250; : 1 worker ZFMK_HYM_2009_6251; : 1 worker ZFMK_HYM_2009_6252; : 2 workers ZFMK_HYM_2009_6149, ZFMK_HYM_2009_6150; : 2 workers ZFMK_HYM_2009_6254; NMK: 3 workers ZFMK_HYM_2009_6146, ZFMK_HYM_2009_6147, ZFMK_HYM_2009_6148; : 1 worker ZFMK_HYM_2009_6253; : 16 workers ZFMK_HYM_2009_6151, ZFMK_HYM_2009_6152, ZFMK_HYM_2009_6153, ZFMK_HYM_2009_6154, ZFMK_HYM_2009_6155, ZFMK_HYM_2009_6156, ZFMK_HYM_2009_6157, ZFMK_HYM_2009_6158, ZFMK_HYM_2009_6159, ZFMK_HYM_2009_6161, ZFMK_HYM_2009_6162, ZFMK_HYM_2009_6168, ZFMK_HYM_2009_6169, ZFMK_HYM_2009_6170, ZFMK_HYM_2009_6171).

Etymology
The new species is dedicated to Barry Bolton, Isle of Wight, United Kingdom, to honour his lifetime dedication on myrmecology. Most actual taxonomic and systematic works would not be possible without his fundamental publications of the last decades.