Octostruma gymnogon Longino

Longino, John T, 2013, A revision of the ant genus Octostruma Forel 1912 (Hymenoptera, Formicidae), Zootaxa 3699, pp. 1-61 : 33

Octostruma gymnogon Longino , sp. nov.

(Figs 1E, 3D, 5D, 24, 42)

Type material. Holotype worker: COSTA RICA, Alajuela: Casa Eladio, Rio Penas Blancas, 10.31667, -84.71667, ± 2 km, 800 m, 26 Apr 1987, primary wet forest, sifted leaf litter (J. Longino#1579-s) [INBC, unique specimen identifier CASENT0627379]. Paratype workers, queen: same data [INBC, CASENT0627380]; same data except (J. Longino#1578-s) [CAS, LACM ENT 143374; USNM, LACM ENT 143375]; 27 Apr 1988 (J. Longino#2015-s) [MCZC, LACM ENT 143379; MZSP, LACM ENT 143380]; 10 May 1989 (J. Longino#2529-s) [UVGC, INBI0CRI001281404; EAPZ, INBI0CRI001281422]; 23 May 1990 (J. Longino#2701-s) [UCDC, INBI0CRI001282517]; 2 Mar 2004 (J. Longino#5278-s) [CAS, JTLC000005383; JTLC, JTLC000005390].

Geographic range. Guatemala to Panama.

Diagnosis. 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. 5D, lacking erect setae on posterolateral margins of head (present in O. balzani, O. megabalzani , and O. trithrix ) and on the posteromedian margin (present in O. amrishi ); mesosomal dorsum lacking a pair of erect setae (present in O. balzani, O. megabalzani , and O. trithrix ); metanotal groove not impressed in profile view (impressed in O. balzani and O. megabalzani ).

Description. Worker. HW 0.62-0.68, HL 0.56-0.59, WL 0.62-0.68, CI 109-114 (n=6). Matching in almost every respect the description for O. balzani , except the differences outlined in the Diagnosis and key. Octostruma gymnogon is generally darker brown than either O. amrishi or O. balzani .

Queen. HW 0.66, HL 0.60, WL 0.79, CI 110 (n=1). Similar in all respects to O. balzani .

Biology. Octostruma gymnogon is a montane species. It occurs mostly in mature cloud forest. On the Barva Transect in Costa Rica it shows a sharp elevationally parapatric distribution with O. amrishi and is restricted to elevations above 400 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. See additional comments under O. balzani .

Etymology. The name refers to the lack of a spatulate seta on the posterolateral vertex margin. It is a noun in apposition and thus invariant.