Octostruma amrishi

Longino, John T, 2013, A revision of the ant genus Octostruma Forel 1912 (Hymenoptera, Formicidae), Zootaxa 3699, pp. 1-61 : 14-16

Octostruma amrishi (Makhan, 2007) Revised Status

(Figs 1E, 3D, 5C, 15, 42)

Pyramica amrishi Makhan 2007:1, figs. 1,2. Holotype worker: Suriname, Kasikasima, 27 Mar 1996 (D. Makhan) [repository unknown; see discussion in Bolton et al., 2008] (not examined). Combination in Octostruma ; junior synonym of Octostruma balzani : Bolton, Sosa-Calvo, et al. 2008: 62. Revised Status.

Geographic range. Honduras to southern Peru and Amazonian Brazil.

Description. Worker. HW 0.54-0.64, HL 0.50-0.60, WL 0.54-0.70, CI 106-110 (n=8). Matching in most respects the description for O. balzani ; mandible with 8 teeth (Fig. 3D), tooth 1 a broad blunt lamella, strongly differentiated from tooth 2, teeth 2-5 acute, similar in shape, with denticles between them; teeth 5-8 forming an apical fork, with 5 and 8 large, 6 and 7 small partially confluent denticles ( O. balzani complex); face setation as in Fig. 5C, lacking erect setae on posterolateral margins of head (present in O. balzani, O. megabalzani , and O. trithrix ), a medial pair present on vertex margin (lacking in O. gymnogon ); mesosomal dorsum usually lacking a pair of erect setae (present in O. balzani, O. megabalzani , and O. trithrix ); metanotal groove usually not impressed in profile view (impressed in O. balzani, O. megabalzani ). When sympatric with O. balzani, O. amrishi is often a lighter red brown.

Queen (previously undescribed). HW 0.60, HL 0.56, WL 0.73, CI 106 (n=1). Similar in all respects to O. balzani .

Biology. Octostruma amrishi is a lowland to lower montane species. It occurs mostly in mature wet forest, less often in second growth forest. In the northern part of the range in Central America, where O. gymnogon does not occur, it extends into cloud forest to 1500 m. In southern Central America, where O. gymnogon occurs, it exhibits an elevationally parapatric distribution with O. gymnogon and is restricted to elevations below 600 m. Almost all collections are from Berlese and Winkler samples of sifted litter and rotten wood from the forest floor. Dealate queens and intercaste workers occasionally occur together with workers in litter samples. One collection was of foragers on clay soil in a rainforest. See additional comments under O. balzani .

Comments. Sampling of Octostruma is less thorough in South America than in Central America, but specimens that match the morphology of O. amrishi occur in lowland to midmontane rainforest in northern South America and throughout the Amazonian lowlands. Specimens from the southern portion of the range, including Amazonian Brazil and the eastern and western foothills of the Ecuadorian Andes, show reduced punctation on the first gastral tergite, becoming smooth and shining on a variable extent of the posterior portion of the tergite. See additional comments under O. balzani .

Although the type of O. amrishi was not examined, if it exists, the characteristic setal pattern can be seen on the figures in the original publication.