Acropyga panamensis

A. panamensis has been collected from leaf litter samples, in rotten logs and under stones from both wet and dry forests. Current collections have all been from 300 meters or below in elevation. Alates (both males and queens) were collected in January from Panama. (LaPolla 2004)

Identification
LaPolla (2004) - Worker: 8 segmented antennae; scape fails to reach posterior margin by about the length of first three funicular segments; mandible with an enlarged, rectangular, apically truncated basal tooth; apical segment is much wider than preceding funicular segments giving it a swollen appearance. Queen: As in worker except for modifications expected for caste; scape is slightly longer than in worker. Male: 10 segmented antennae; basal tooth, as in other castes, though not as prominent; antennal shape also as in other castes; digiti long, thick and with rounded apices; cuspi significantly shorter, bending toward digiti at about half of digiti length. This species is unique in its appearance.

A. panamensis is easy to recognize with its distinctively large apical antennal segments, short scapes, and enlarged, rectangular, truncated basal teeth. The basal tooth of A. panamensis is not unique among species in the genus. In the New World, Acropyga tricuspis possesses a large basal tooth similar to A. panamensis, though the former species has 3 distinct cusps on the basal tooth and it is more square in shape than rectangular. Species belonging to the butteli species-group all possess enlarged, rectangular, truncated basal teeth similar to A. panamensis as well, but they do not appear to be closely related.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Guatemala, Guyana, Mexico, Panama.

From LaPolla (2004): This species has been found primarily in Costa Rica and Panama, but its recent collection in Guyana suggests it has a much larger range than is presently known.

Biology
Jack Longio: This species occurs in moist forest habitats of Costa Rica's Pacific lowlands. Longino found two colonies under stones in the "bosque humedo" of Santa Rosa National Park, on 15 July 1985. One nest contained alate queens and males. Workers were also collected in a Winkler sample of sifted leaf litter from Sirena in Corcovado National Park.

Morphology
LaPolla (2004) - The closest relative to A. panamensis is Acropyga ayanganna (see discussion for A. ayanganna for further discussion), a species whose basal tooth is of a more "typical" form. What this suggests is that enlarged basal teeth have evolved at least 3 independent times in the genus. Outside of Acropyga I have also observed a similarly shaped basal teeth in an Afrotropical Pseudolasius species. Why this tooth structure has evolved multiple times in the genus is unclear, and unfortunately our present knowledge of all Acropyga with enlarged basal teeth is very limited.

Nomenclature

 * . Acropyga (Rhizomyrma) panamensis Weber, 1944: 113, fig. 24 (w.) PANAMA (Barro Colorado I.).
 * LaPolla, 2004a: 73 (q.m.).
 * Status as species: Kempf, 1972a: 17; Bolton, 1995b: 58; LaPolla, 2004a: 72 (redescription); Branstetter & Sáenz, 2012: 255.

Worker
LaPolla (2004) - (n=5): TL: 1.39-1.58; HW: 0.315-0.393; HL: 0.41-0.457; SL: 0.21-0.266; ML: 0.39-0.45; GL: 0.546-0.718; CI: 76.83-86.0; SI: 63.35-74.51.

Head: brownish-yellow; head distinctly longer than broad; covered in thick layer of short appressed hairs; posterior margin entire; 8 segmented, extremely incrassate antennae; apical segment more than twice as wide as pedicel and about as long as all other funicular segments combined, giving it a swollen appearance; scape short, fails to reach posterior margin by about the length of the first three funicular segments; clypeus convex medially, with several long erect hairs on surface; mandible broad with 4 teeth; the basal tooth enlarged, rectangular, and apically truncated; inner mandibular margin and anterior clypeal margin parallel. Mesosoma: brownish-yellow; in lateral view entire mesosoma appears roughly rectangular; pronotum in lateral view, with short anterior shelf then rising steeply toward mesonotum; pronotum covered in a dense layer of short hairs; pronotum distinctly rounded posteriorly; entire dorsum nearly flat; mesonotum covered in thick layer of short appressed hairs; propodeum not much lower than mesonotum, with a thick layer of short appressed hairs; propodeum strongly rounded posteriorly with steep declivity. Gaster: petiole thick and erect, roughly triangular in lateral view; gaster brownish-yellow; covered in a layer of short appressed hairs, with scattered suberect to erect hairs throughout.

Queen
LaPolla (2004) - (n=4): TL: 1.97-2.54; HW: 0.391-0.42; HL: 0.474-0.508; SL: 0.313-0.326; ML: 0.566-0.732; GL: 0.899-1.35; CI: 79.8-83.54; SI: 77.62-80.05. As in worker with differences associated with caste and with the following differences: scape slightly longer than in worker, only fails to reach posterior margin by about length of pedicel; mesonotum higher than propodeum which is nearly flat.

Male
LaPolla (2004) -(n=2): TL: 1.65-1.8; HW: 0.297-0.312; HL: 0.345-0.354; SL: 0.191-0.197; ML: 0.561-0.605; GL: 0.739-0.849; CI: 83.89-94.43; SI: 61.22-66.33

Head: brownish-yellow, becoming dark brown around 3 prominent ocelli; covered in short suberect to erect hairs; eyes prominent; 10 segmented, incrassate antennae; apical segment wide, about as long as preceding four segments; scape fails to reach posterior margin by about length of pedicel; clypeus slightly convex medially, with numerous erect hairs on surface; mandible with 2 teeth, the basal tooth as in worker, though not as long and less distinct. Mesosoma: brownish-yellow to brown; pronotum small and collar-like, overarched by mesonotum; mesonotum flat and covered in short hairs; scutellum with longest erect hairs; propodeum small and rounded with short, but distinct declivity. Gaster: petiole thick and erect, short and wide; gaster largely dark brown, covered in a thick layer of appressed hairs, with scattered suberect to erect hairs throughout. Genitalia: parameres taper to points caudally; posterior end (last 1/3 of length) with many long hairs; cuspi short, nearing lower half of digiti, with prominent teeth at apices; digiti much longer than cuspi, thick and rounded apically; near cuspi, digiti with prominent teeth, the last few as high as cuspi teeth;

Type Material
Acropyga (Rhizomyrma) panamensis Weber, 1944: 113. Neotype worker, PANAMA: Barro Colorado Island; Canal Zone; B41 (W.L. Brown and E.S. McCluskey) (MCZC). This species was described by Weber (1944) from a single worker specimen, which has subsequently been lost (though the pin remains the specimen does not). In the interest of nomenclatural stability a neotype is designated. The neotype is from the original type locality. The neotype is labeled JSL TYPE #123.

References based on Global Ant Biodiversity Informatics

 * Basset Y., L. Cizek, P. Cuenoud, R. K. Didham, F. Guilhaumon, O. Missa, V. Novotny, F. Odegaards, T. Roslin, J. Schmidl et al. 2012. Arthropod diversity in a tropical forest. Science 338(6113): 1481-1484.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * 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.
 * Longino J. T. 2013. Ants of Honduras. Consulted on 18 Jan 2013. https://sites.google.com/site/longinollama/reports/ants-of-honduras
 * Longino, J.T. 2010. Personal Communication. Longino Collection Database
 * Silva R.R., and C. R. F. Brandao. 2014. Ecosystem-Wide Morphological Structure of Leaf-Litter Ant Communities along a Tropical Latitudinal Gradient. PLoSONE 9(3): e93049. doi:10.1371/journal.pone.0093049