Crematogaster volamena

Crematogaster volamena is currently known from about 10 localities along the eastern rainforest belt in Madagascar. Here the species occurs in low- to mid-elevation rainforest or littoral forest. Crematogaster volamena appears to be a generalist in terms of nesting preferences, as it has been collected both nesting arboreally in dead twigs and on the ground in rotten logs. Scant natural history information exists, but noteworthy is a size variation in workers of this species that is reminiscent of a major-minor distinction in other ant genera. The larger workers have a distinctly enlarged head and more powerful mandibles compared to regular workers, and they are more rarely seen throughout collections. These individuals do not share the attributes of the intermediates described here for Crematogaster rasoherinae and Crematogaster madecassa, such as presence of ocelli, or a queen-like modified mesosoma. (Blaimer 2012)

Identification
Blaimer (2012) - Workers of C. volamena are diagnosed most easily by their indistinct occipital carinae, the non-protruding and small eyes and the absence of raised, sharp lateral carinae on the propodeum. All these characteristics are shared with the much rarer, but closely resembling Crematogaster mpanjono, from which it cannot be distinguished reliably based on the worker caste. Crematogaster volamena has slightly longer propodeal spines than C. mpanjono, and the propodeum is lacking longer erect pilosity. The two species are not known to co-occur, and therefore their distributions can help in distinguishing between them. Queens of C. volamena are readily separated from C. mpanjono queens by virtue of their well pronounced occipital carinae and a scuto-scutellar suture that is broadly meeting the mesoscutum. From the remaining Malagasy Orthocrema queens, C. volamena queens are differentiated by the absence of propodeal spines and their large size (HW 1.72, WL 2.61).

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  volamena. Crematogaster volamena Blaimer, 2012: 59, figs. 31-32 (w.q.m.) MADAGASCAR.

Worker
(n=20). Holotype: HW 0.62; HL 0.59; EL 0.11; SL 0.50; WL 0.66; SPL 0.06; PTH 0.13; PTL 0.20; PTW 0.20; PPL 0.10; PPW 0.21; LHT 0.49; CI 1.04; OI 0.19; SI 0.85; SPI 0.09; PTHI 0.65; PTWI 0.99; PPI 2.07; LBI 1.35.

Other material. HW 0.66–0.98; HL 0.62–0.95; EL 0.12–0.18; SL 0.50–0.66; WL 0.68–0.92; SPL 0.05–0.09; PTH 0.13–0.19; PTL 0.21–0.30; PTW 0.21–0.30; PPL 0.11; PPW 0.20–0.32; LHT 0.42–0.72; CI 1.03–1.13; OI 0.18–0.22; SI 0.73–0.84; SPI 0.06–0.12; PTHI 0.50–0.72; PTWI 0.82–1.08; PPI 1.43–2.13; LBI 1.25–1.71.

Very small to medium sized species (HW 0.62–0.98, WL 0.66–0.92), with characters of the C. volamena-group, in addition to the following. Clypeus with several (up to 6), irregular vertical carinae.

Mesonotum transversely concave between lateral carinae.

Head sculpture aciculate; longer, erect pilosity absent from propodeum. Color golden yellow or (more rarely) medium brown.

Queen
(n=1). HW 1.72, HL 1.60, EL 0.37, SL 0.90, MSNW 1.28, MSNL 1.59, WL 2.61, SPL 0.00, PTH 0.39, PTL 0.67, PTW 0.61, PPL 0.43, PPW 0.65, LHT 1.21, CI 1.08, OI 0.23, SI 0.56, MSNI 1.64, SPI 0.15, PTHI 0.59, PTWI 0.91, PPI 1.50, LBI 2.16.

Queen description Large (HW 1.72, WL 2.61), with characters of the C. volamena-group, in addition to the following. Antennal scapes reaching to about level of median ocelli; occipital carinae well pronounced; eyes medium-sized (OI 0.23); head wider than long (CI 1.08).

Mesosoma compact (MSNI 1.64, WL 2.61); mesoscutum in dorsal view oval; scuto-scutellar suture broadly meeting mesoscutum; dorsal face of propodeum short but distinct, posterior face sloping abruptly; petiole in dorsal view oval; wings smoky.

Head sculpture carinulate-aciculate. Color brown with yellow markings on meso-, metasoma and legs.

Male
(n=1). HW 0.68, HL 0.52, EL 0.26, SL 0.11, MSNW 0.73, MSNL 0.75, WL 1.44, SPL 0.00, PTH 0.19, PTL 0.31, PTW 0.22, PPL 0.15, PPW 0.26, LHT n.a., CI 1.30, OI 0.50, SI 0.21, MSNI 1.93, SPI 0.62, PTHI 0.62, PTWI 0.71, PPI 1.71, LBI n.a.

Small (HW 0.68, WL 1.44). Masticatory margin of mandibles with 2 teeth; eyes large (OI 0.50) and protruding, situated slightly below midline of head, and not approaching clypeal margin; antennae 11–12-segmented (separation between 3rd and 4th funicular segment is incomplete in the examined specimen), scapes very short (SI 0.21), 2nd funicular segment globular, last 2 or 3 funicular segments compressed (this may be post mortem); head strongly wider than long (CI 1.30), mostly due to lateral extent of eyes; ocellar triangle extending to posterior head margin in full face view like a crown; occipital carinae distinct.

Mesosoma compact (MSNI 1.93, WL 1.44); mesoscutum in dorsal view as wide as long; scutellum with only one long and flat dorsal face, in dorsal view oval-shaped and posteriorly rounded, dorsoposterior margin not carinate; dorsal face of propodeum about as long as posterior face; propodeal spines absent; petiole in dorsal view oval, carinae or denticles absent and all margins rounded, in lateral view petiole anteriorly tapering; anteroventral subpetiolar tooth absent; postpetiole fairly globular, median impression absent; wings clear.

Head sculpture rugulose, mesoscutum aciculate, scutellum longitudinally carinulate, petiole and postpetiole rugulose-shiny; face with fairly abundant longer erect pilosity; mesoscutum with dense long erect pilosity; posterior part of scutellum with sparse long pilosity; petiole and postpetiole without distinct dorsoposterior setae, but abundant erect pilosity laterally. Color dark brown.

Type Material
MADAGASCAR: Toliara: Forêt Ivohibe: -24.56900, 47.20400, 200m, rainforest, malaise trap, 2.-4.xii.2006, B. L. Fisher et al.

Holotype worker: pinned, CASENT0125748, BLF15448, malaise trap; original locality label: MADG’R: Toliara, Forêt Ivohibe, 200m, 24°34.14S, 47°12.24E, 2–4.xii.06, rainforest, Fisher et al. BLF15448; deposited at. 4 paratype workers: #1: pinned, CASENT0128455, BLF15450, sifted litter (leaf mold, rotten wood); same locality data as holotype; deposited at. #2: pinned, CASENT0488904, BLF08006(23), beating low vegetation, rainforest; original locality label: MADG’R: Prov. Toamasina, Mont. Anjanaharibe, 18.0 km, 21° NNE Ambinanitelo 470m 15°11.3'S, 49°36.9'E, 8–12.iii.2003 Fisher et al. BLF8006; deposited at. #3: pinned, CASENT0071334, BLF12557, malaise trap; original locality label: MADG’R: Prov. Toamasina, P.N. Mananara-Nord, 16°27.3'S, 49°47. 25'E, 225m, 14.xi.2005, malaise, rainforest, Fisher et al. BLF12557; deposited at. #4: pinned, CASENT0488765, BLF8251(4), beating low vegetation; original locality label: MADG’R: Prov. Toamasina, Mont. Akirindro 7.6 km 341° NNW Ambinanitelo 15°17.3'S, 49°32.9'E 600m, 17–21.iii.2003, Fisher et al. BLF8251; deposited at.

Etymology
This species is named for the golden yellow coloration that most of its workers possess, as “volamena” means “gold” in Malagasy. This name should be treated as a noun in apposition.