Rhopalothrix subspatulata

Longino and Boudinot (2013) - This species occurs in lowland rainforest, from 50–800m elevation. Of the approximately 50 workers known, one was collected in a Malaise trap sample and the rest were in Berlese or Winkler samples. The Winkler samples were of sifted litter and rotten wood on the forest floor; the Berlese samples were cores of forest floor litter and about 5–10cm of the mineral soil beneath. At La Selva Biological Station, 3% of 208 Berlese samples and 2% of 640 miniWinkler samples contained workers. Given that each miniWinkler sample covered an area about 60 times greater than a Berlese sample (1 sq. m versus 165 sq. cm), R. subspatulata was far more abundant in Berlese samples. This suggests that R. subspatulata, and perhaps Rhopalothrix in general, are subterranean, nesting and foraging in mineral soil, and perhaps only rarely venturing up into the litter layer. The pale color and greatly reduced eyes also suggest subterranean habits.

Alate queens were collected in three of 50 canopy fogging samples from the ALAS project at La Selva: 8 October and 10 November 1994 and 28 December 1999 (mid to late wet season). This suggests that the species mates above ground and has normally dispersing queens.

Identification
Sharing with R. nubilosa and Rhopalothrix weberi a characteristic labrum shape: anterior margin of labrum with two long, bluntly triangular lobes, sinus between them deep, length of anterolateral lobe longer than or about equal to distance from base of sinus to transverse carina at base of labrum; worker hardly differing from R. weberi, being slightly larger (HW > 0.40) and with larger mandibular teeth; queen differing from R. weberi in stronger facial concavity and carina medial to compound eye; worker differing from Rhopalothrix nubilosa in smaller size (< 0.50) and fewer squamiform setae on first gastral tergite (six versus about twelve).

Key to Rhopalothrix workers

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Nicaragua.

Castes
Males are unknown.

Nomenclature

 *  subspatulata. Rhopalothrix subspatulata Longino & Boudinot, 2013: 316, figs. 1D, 2D, 3B, 4, 12, 16 (w.q.) COSTA RICA.

Worker
HW 0.42–0.49 (n=14); mandible with two closely-spaced short triangular teeth at base, a smaller tooth about mid-distance between basal teeth and base of subapical tooth, reclinate denticle at base of subapical tooth absent, apical tooth short, about 1/3 × length of subapical tooth, intercalary teeth minute; labrum about as long as broad, with two long, bluntly triangular lobes, sinus between them deep, length of anterolateral lobe longer than or about equal to distance from base of sinus to transverse carina at base of labrum; erect setae on leading edge of scape stiff but narrow, hardly clavate, unlike the squamiform setae typical of many other species; arcuate promesonotal groove and metanotal groove moderately impressed; propodeal tooth right angled, infradental lamella thin, evenly and shallowly concave; first gastral tergite with four squamiform setae on posterior margin, two at mid-disk.

Queen
HW 0.51–0.53 (n=2); mandible and labrum similar to worker; face shape similar to worker but with large, shallow, circular concavity medial to compound eye, separated from eye by distinct slightly elevated carina that partially covers eye in full face view; compound eye longer than maximum width of scape; ocelli small, cuticle adjacent to ocelli marked with black pigment spots on evenly light brown background; shape of propodeal tooth, infradental lamella, petiole and postpetiole similar to worker; katepisternum and anepisternum large, convex, separated by thin groove; pubescence layer of abundant, short, curved setae covers mandible, face, scapes, legs, dorsal mesosoma and metasoma; abundant stiff erect setae on face, anterior edge of scape, side of head, dorsal mesosoma, dorsal gaster.

Fore wing: pterostigma placed about 3/5 the length of the costal margin; veins Sc+R, M+Cu, 1A, and crossvein 2rs-m tubular; 2rs-m terminating posteriorly as a node; veins Rs, M, and Cu nebulous; Rs+M spectral; vannal region vestigial; only basal and submarginal 1 cells enclosed by tubular or nebular veins. Hind wing: only veins C+Sc+R and 1A tubular, and only for a very short length of the remigium; veins Sc+R, M+Cu, R, Rs and crossvein 2rs-m nebulous; no cells are closed; vannal region vestigial.

Type Material
Holotype worker: Costa Rica, Heredia: La Selva Biological Station, 10.43333 -84.01667 ±1.5 km, 50 m, 1 Feb 1994, rainforest, ex Berlese of litter and soil (ALAS#B/05/381), unique specimen identifier INBIOCRI001259541. Paratypes (workers): same data as holotype, INBIOCRI001259538; , INBIOCRI001259539; , INBIOCRI001259540; , INBIOCRI001259542; same data but 15 Apr 1993 (ALAS#B/05/053) , INBIOCRI002281441.

Etymology
Referring to the sparse spatulate setae on the gaster.