Tetramorium rubrum

Identification
Tetramorium rubrum can be well separated from other species of the complex by the following character combination: CI 87 - 91; clypeus with distinct median longitudinal ruga; antennal scape relatively long (SI 85 - 93); eyes moderate (OI 23 - 26); metanotal groove in profile hardly impressed; whole body with simple subdecumbent to erect pilosity; coloration red-brown.

Distribution
Known from Cameroun, Ghana, Ivory Coast and Nigeria.

This taxon was described from Cameroun.

Nomenclature

 *  rubrum. Tetramorium rubrum Hita Garcia, Fischer & Peters, 2010b: 36, figs. 22B, 23B, 24A, 40-42 (w.) CAMEROUN.

The material described here as T. rubrum has previously been listed as Tetramorium edouardi. Comparison of the West African material with the holotype from Ethiopia revealed great differences that made the description of the West African specimens as T. rubrum necessary. Both species share many morphological similarities and show a low degree of specialized characters within the edouardi complex. Nonetheless, T. rubrum possesses distinctly longer antennal scapes (SI 85 - 93) and head (CI 87 - 91) than T. edouardi (SI 76 - 83, CI 90 - 96). Additionally, the metanotal groove of T. rubrum in profile is at most barely impressed whereas in T. edouardi it is distinctly impressed. Also the coloration seems to be quite different: dark red-brown in T. rubrum as opposed to the dark brown, nearly black, colour in T. edouardi (see note under T. edouardi concerning the colour of the holotype). The same character combination divides T .rubrum from T. robertsoni from Tanzania since the latter and T. edouardi are morphologically relatively close. One could argue that T. rubrum could be only a geographic variation of T. edouardi or T. robertsoni since it occurs only in West Africa while the other two species seem to be restricted to Eastern Africa. However, the morphological, and especially the morphometric, differences are plausible and show a higher degree of dissimilarity than generally observed in the geographic variability of most other weitzeckeri group species.

Furthermore, moderately sized eyes (OI 23 - 26) and an uniform coloration distinguish T. rubrum from T. philippwagneri (OI 21 - 22) and T. schoutedeni (OI 22). In addition, T. rubrum possesses simple long hairs that separate it straightforwardly from T. mkomazi that has no pilosity except on the head, and from the species with bizarrely modified pilosity, T. pinnipilum, T. rogatum, and T. zonacaciae.

Worker
HL 0.867 - 0.994 (0.933); HW 0.756 - 0.900 (0.832); SL 0.656 - 0.778 (0.731); EL 0.189 - 0.222 (0.207); PW 0.600 - 0.689 (0.655); WL 1.044 - 1.238 (1.143); PSL 0.267 - 0.339 (0.299); PTL 0.233 - 0.300 (0.277); PTH 0.356 - 0.422 (0.386); PTW 0.278 - 0.356 (0.321); PPL 0.278 - 0.356 (0.321); PPH 0.322 - 0.411 (0.374); PPW 0.383 - 0.467 (0.432); CI 87 - 91 (89); SI 85 - 93 (88); OI 23 - 26 (25); PSLI 30 - 35 (32); PeNI 44 - 54 (49); LPeI 66 - 79 (71); DPeI 110 - 121 (116); PpNI 62 - 71 (66); LPpI 79 - 92 (86); DPpI 128 - 146 (135); PPI 129 - 145 (135) (33 measured).

Head longer than wide (CI 87 - 91). Anterior clypeal margin with broad median impression. Frontal carinae strongly developed, less strongly developed behind level of eye, ending shortly before posterior margin of head. Antennal scrobe shallow, narrow, and without defined posterior and ventral margins, ending before posterior margin of head. Antennal scape relatively long, not reaching posterior margin of head (SI 85 - 93). Eyes moderate (OI 23 - 26), with 11 to 13 ommatidia in longest row. In profile metanotal groove not or hardly impressed. Propodeal spines long and spinose (PSLI 30 - 35). Propodeal lobes small, triangular and acute. Petiolar node high nodiform, in dorsal view only slightly wider than long (DPeI 110 - 121), in profile between 1.3 and 1.5 times higher than long (LPeI 66 - 79); posterodorsal angle of node weaker developed and more rounded than anterodorsal, dorsum sloping faintly downwards posteriorly. Postpetiole in dorsal view between 1.2 to 1.5 times wider than long (DPpI 128 - 146); in lateral view rounded, around 1.1 to 1.2 times higher than long (LPpI 79 - 92). Mandibles longitudinally rugose. Clypeus usually with 5 or more longitudinal rugae, median ruga always strongly developed and unbroken. Head mostly longitudinally rugose with 9 to 12 (generally 10) widely spaced longitudinal rugae between frontal carinae, rugae near posterior margin of head with many cross-meshes. Mesosoma generally with longitudinal rugulation, in dorsal view anterior pronotum often partly rugo-reticulate, propodeal declivity unsculptured. Ground sculpturation on head and mesosoma smooth and shiny. Petiole and postpetiole rugo-reticulate; postpetiole less strongly sculptured; gaster completely unsculptured, smooth and shiny. All dorsal surfaces of head, mesosoma, both waist segments and gaster with numerous long, simple, suberect to erect hairs. Fine pubescence and antennal scapes appressed to suberect, on tibiae appressed to decumbent. Coloration red-brown, appendages of lighter colour.

Etymology
The species epithet is a Latin adjective and refers to the coloration of the new species which is of an intensive dark red.

Type Material
Holotype worker, CAMEROON, Yaounde, 30.III.1990, leg. A. Dejean, (: ZFMK_HYM_2009_6209). Paratypes, 36 workers with same data as holotype (BMNH: 3 workers ZFMK_HYM_2009_6227, ZFMK_HYM_2009_6228, ZFMK_HYM_2009_6229; CASC: 6 workers ZFMK_HYM_2009_6231, ZFMK_HYM_2009_6232, ZFMK_HYM_2009_6233; : 2 workers ZFMK_HYM_2009_6225, ZFMK_HYM_2009_6226; LACM: 2 workers ZFMK_HYM_2009_6234; MHNG: 4 workers ZFMK_HYM_2009_6219, ZFMK_HYM_2009_6220; NHMB: 3 workers, ZFMK_HYM_2009_6236; NMK: 2workers ZFMK_HYM_2009_6237; SAMC: 2 workers ZFMK_HYM_2009_6235; ZFMK: 12 workers ZFMK- ZFMK_HYM_2009_6210, ZFMK_HYM_2009_6211, ZFMK_HYM_2009_6213, ZFMK_HYM_2009_6214, ZFMK_HYM_2009_6215, ZFMK_HYM_2009_6216, ZFMK_HYM_2009_6217, ZFMK_HYM_2009_6218, ZFMK_HYM_2009_6221, ZFMK_HYM_2009_6222, ZFMK_HYM_2009_6223, ZFMK_HYM_2009_6224).