Tetramorium intermedium

Collected from forest leaf-litter.

Identification
Tetramorium intermedium can be well distinguished from other species of the complex because it is the only one with an antennal scape of medium length (SI 74 - 81) and head and mesosoma fully packed with widely spaced longitudinal rugae.

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

Distribution based on Regional Taxon Lists
Afrotropical Region: Ghana.

Nomenclature

 *  intermedium. Tetramorium intermedium Hita Garcia, Fischer & Peters, 2010b: 48, figs. 5B, 55-57 (w.) GHANA.

Type Material

 * Paratypes, 8 workers with same data as holotype (: ZFMK_HYM_2009_6114, ZFMK_HYM_2009_6115, ZFMK_HYM_2009_6116, ZFMK_HYM_2009_6121); 9 workers from GHANA, Atewa Forest Reserve, nr. Kibi, ex leaf litter, 26.II.1992, leg. R. Belshaw (: 6 workers ZFMK_HYM_2009_6118, ZFMK_HYM_2009_6120; : 1 worker ZFMK_HYM_2009_6122; : 1 worker ZFMK_HYM_2009_6123; : 1 worker ZFMK_HYM_2009_6119); 3 workers from GHANA, Bunso nr. Tafo, 17.IV.1992, leg. R. Belshaw (: ZFMK_HYM_2009_6117); and 3 workers from GHANA, Kade, X.1992, leg. R. Belshaw (: ZFMK_HYM_2009_6185).
 * Paratypes, 8 workers with same data as holotype (: ZFMK_HYM_2009_6114, ZFMK_HYM_2009_6115, ZFMK_HYM_2009_6116, ZFMK_HYM_2009_6121); 9 workers from GHANA, Atewa Forest Reserve, nr. Kibi, ex leaf litter, 26.II.1992, leg. R. Belshaw (: 6 workers ZFMK_HYM_2009_6118, ZFMK_HYM_2009_6120; : 1 worker ZFMK_HYM_2009_6122; : 1 worker ZFMK_HYM_2009_6123; : 1 worker ZFMK_HYM_2009_6119); 3 workers from GHANA, Bunso nr. Tafo, 17.IV.1992, leg. R. Belshaw (: ZFMK_HYM_2009_6117); and 3 workers from GHANA, Kade, X.1992, leg. R. Belshaw (: ZFMK_HYM_2009_6185).

The new species shows an extraordinary character combination for the muralti complex. Within this complex it is the only species with fully longitudinally rugose head and mesosoma although this character is more typical of the edouardi and weitzeckeri complexes. Another character that divides T. intermedium from the remainder of the muralti complex is the moderately sized antennal scape (SI 74 - 81) that is distinctly longer than in all other muralti complex species that all possess short scapes (SI 63 - 73). This character is also more representative for the other 2 species complexes. A third important character is the shape of the petiolar node which is thickly squamiform (DPeI 179 - 212, LPeI 41 - 45), and not far from being high nodiform, typical for the  edouardi complex. Only T. akengense shows a similarly thick petiole but this species cannot be confused with T. intermedium because of its reduced sculpturation. Nonetheless, T. intermedium is considered to belong to the muralti complex because it shares the key diagnostic character, the well-developed antennal scrobe with distinct and sharp margin all around. Taking into consideration the description of T. intermedium it shares more important characters with the muralti complex than with both other complexes.

Worker
HL 0.528 - 0.578 (0.556); HW 0.494 - 0.533 (0.521); SL 0.367 - 0.422 (0.406); EL 0.117 - 0.133 (0.124); PW 0.394 - 0.422 (0.412); WL 0.622 - 0.700 (0.670); PSL 0.133 - 0.161 (0.146); PTL 0.094 - 0.106 (0.099); PTH 0.222 - 0.244 (0.234); PTW 0.178 - 0.211 (0.193); PPL 0.150 - 0.194 (0.170); PPH 0.200 - 0.244 (0.229); PPW 0.222 - 0.256 (0.241); CI 90 - 96 (94); SI 74 - 81 (78); OI 22 - 25 (24); PSLI 24 - 29 (26); PeNI 45 - 50 (47); LPeI 41 - 45 (43); DPeI 179 - 212 (195); PpNI 56 - 61 (58); LPpI 66 - 84 (74); DPpI 126 - 153 (141); PPI 116 - 131 (125) (19 measured).

Head longer than wide (CI 90 - 96). Anterior clypeal margin entire and generally convex. Frontal carinae strongly developed and sinuate, curving down ventrally shortly before posterior margin of head to form the posterior and ventral margins of antennal scrobe. Scrobe well-developed, broad and relatively deep, with distinct sharp margin all around. Antennal scape moderate (SI 74 - 81). Eyes moderate to large (OI 22 - 25), with 7 to 9 ommatidia in longest row. Metanotal groove in profile not impressed. Propodeal spines long and spinose (PSLI 24 - 29). Propodeal lobes small and triangular and acute. Petiolar node thickly squamiform, in dorsal view between 1.8 to 2.1 times wider than long (DPeI 179 - 212) and around 2.2 to 2.5 times higher than long (LPeI 41 - 45). Postpetiole rounded, in dorsal view between 1.2 and 1.5 times wider than long (DPpI 126 - 153); in profile generally around 1.2 to 1.5 times higher than long (LPpI 66 - 84). Mandibles unsculptured, smooth and shiny. Clypeus with 3 unbroken longitudinal rugae. Head longitudinally rugose, generally with 6 widely spaced rugae between frontal carinae, sometimes interrupted or short, antennal scrobe with median longitudinal carina anteriorly running at most to posterior eye level, spaces between rugae and scrobal area unsculptured and shiny. Mesosoma laterally and dorsally longitudinally rugose, too, with 6 or more rugae on dorsum of mesosoma; ground sculpturation smooth and shiny. Petiole, postpetiole, and gaster completely unsculptured, smooth and shiny. All dorsal surfaces with simple, fine, standing hairs. Fine pubescence on tibiae and antennal scapes appressed to subdecumbent. Colour uniformly brown, appendages much lighter brown.

Etymology
The new species is, as noted above, quite unusual in its character combination, and, although a clear member of the muralti complex, shows some tendencies towards the other two species complexes. The species epithet accounts for this intermediate position.

References based on Global Ant Biodiversity Informatics

 * Hita Garcia F., G. Fischer, and M. K. Peters. 2010. Taxonomy of the Tetramorium weitzeckeri species group (Hymenoptera: Formicidae) in the Afrotropical zoogeographical region. Zootaxa 2704: 1-90.