Acropyga palaga

According to label data it has been collected at coffee roots. Males were collected in both April and August, apparently from nests.

Identification
LaPolla (2004) - Worker: 9-10 segmented antennae (but see description); metanotal area distinct; mandibles with 3 distinct teeth; otherwise as in Acropyga goeldii. Queen: unknown. Male: 12 segmented antennae; parameres rectangular, about the same width throughout length; penis valves sharply curved ventrally from tip of penis to ventral extension. Compare with A. goeldii and other members of the goeldii complex.

Based on samples I have examined, workers of A. palaga are virtually indistinguishable from Acropyga goeldii. One possible way to distinguish workers is by the shape of the clypeus. In A. goeldii the posterior clypeal margin rises slightly toward the torulae and is wider, whereas in A. palaga the posterior clypeal margin is strictly transverse toward the torulae and is narrower. However, the extent to which both species vary is not possible to assess at this time due to the low number of specimens available for study. Another worker character that appears to be stable for A. palaga is that of the distinct metanotal area (with two sulci present), but A. goeldii may sometimes possess a distinct metanotal area. A. palaga appears to possess fewer hairs on the mesosoma than A. goeldii, but given the variation observed in A. goeldii the utility of this character remains unclear.

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

This species has only been collected from two localities in Costa Rica.

Nomenclature

 *  palaga. Acropyga palaga LaPolla, 2004a: 54, figs. 21, 39, 45 (w.m.) COSTA RICA.

Despite similarities in workers, examination of males suggests at least two species are present (see A. goeldii discussion for more detail). A. palaga males possess rectangular parameres in which width does not change much across their length. This in contrast to A. goeldii males in which the parameres typically decrease in width toward the apex. Once dissected the penis valves are distinct from A. goeldii, with a curved ventral aspect from the penis valve tip through the ventral extension. The dorsal margins of A. palaga penis valves are nearly straight, whereas A. goeldii possesses a humped dorsal margin. Additionally, the penis valves also exhibit a straight margin toward the apodeme from the ventral portion of the ventral extension. Finally, A. palaga possesses a ventral extension that narrows significantly toward the base, unlike A. goeldii.

I did notice some variation in paramere width between the two populations of A. palaga examined. Specimens from Alajuela, Costa Rica had wider parameres than those from Estrella Valley, Costa Rica. The penis valves from the Alajuela specimens were not quite as curved at the penis valve caudal ends as the Estrella specimens. Despite those differences both populations had males with a more or less parallel dorsal margins and narrow, curved ventral extensions. The agreement of those characters with each population has led me to consider them the same species. But as more specimens become available for study, variation can be more accurately addressed and changes may be necessary in the taxonomy.

Worker
(n=8): TL: 1.97-2.5; HW: 0.52-0.608; HL: 0.504-0.6; SL: 0.344-0.472; ML: 0.573-0.706; GL: 0.869-1.18; CI: 99.62-104.65; SI: 66.15-77.76.

Head: yellow; head about as broad as long; posterior margin slightly concave; covered in a layer of short appressed hairs, with several erect hairs usually along posterior margin; 9-10 segmented, incrassate antennae (males have 12 segments, so it is likely this species can have workers with up to 11 segments); scape fails to reach posterior margin by less than half length of pedicel; clypeus convex and narrow, covered with abundant erect hairs; mandible with 3 distinct teeth; gap exists between anterior clypeal margin and inner mandibular margin. Mesosoma: yellow; in lateral view pronotum with a short anterior shelf before rising sharply toward mesonotum; posterior pronotum with many erect hairs; mesonotum covered in a thick layer of appressed hairs, with scattered erect hairs; mesonotum higher than propodeum; metanotal area distinct; propodeum rounded with a thick layer of appressed hairs; declivity steep. Gaster: petiole thick and erect; petiole does not reach level of propodeum; gaster yellow; covered in a layer of appressed hairs, with scattered erect hairs throughout.

Queen
Queens are not known for this species.

Male
(n=8): TL: 2.23-2.46; HW: 0.425-0.473; HL: 0.424-0.494; SL: 0.398-0.426; ML: 0.794-0.854; GL: 0.91-1.24; CI: 86.03-101.5; SI: 89.03-103.29.

Head: brownish-yellow to brown, darkest at apex around 3 prominent ocelli; head longer than broad, becoming broader toward apex; covered in a layer of short appressed hairs; 12 segmented, slightly incrassate antennae, apical segment about as long as proceeding 2 segments; scape surpasses posterior margin by about length of pedicel; clypeus narrow, convex medially, covered in thick layer of erect hairs; mandible with 3 distinct teeth; a gap exists between anterior clypeal margin and inner mandibular margin. Mesosoma: brownish-yellow; pronotum short and collar-like; mesonotum anteriorly rounded, dorsally flat, covered in layer of short appressed hairs, with widely scattered erect hairs; propodeum low, with indistinct declivity. Gaster: petiole thick and erect; gaster brownish-yellow, covered in layer of appressed hairs, with scattered erect hair throughout. Genitalia: in lateral view, parameres long, rectangular, with scattered erect to suberect hairs; cuspi long, cylindrical; digiti with long, stalk-like posterior portion, apices anvil-shaped; digiti meet cuspi dorsally, where both have structures have a series of short, peg-like teeth.

Type Material
Holotype worker, COSTA RICA: Estrella Valley (W.M. Mann) (USNM); 3 paratype workers, 6 paratype males, same locality as holotype (USNM) (MCZC). The holotype is labeled JSL TYPE # 105.

Etymology
The specific epithet palaga is Latin for an ingot of gold, in reference to the yellowish color of the workers.

References based on Global Ant Biodiversity Informatics

 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * LaPolla J.S. 2004. Acropyga (Hymenoptera: Formicidae) of the world. Contributions of the American Entomological Institute 33(3): 1-130.