Acropyga exsanguis

LaPolla (2004) - Bünzli (1935) extensively documented the natural history of A. exsanguis (under the synonym A. paramaribensis). This species is highly polygynous. Bünzli found both pleometrosis (founding of a colony by multiple queens), and the acquisition of young queens by established colonies in A. exsanguis, suggesting multiple possible origins of polygyny. Bünzli found that A. exsanguis possesses large, diffuse nests in the soil (similar to those described by LaPolla et al. (2002) for Acropyga epedana). The species is known to make vertical nest movements in the soil depending on soil conditions. For instance, as the upper layers of soil dry, Bünzli found the ants moved deeper into the ground.

Identification
LaPolla (2004) - Worker: 8-9 segmented antennae; scape typically slightly fails posterior margin; head about a broad as long; head width < than 0.52 mm; mandible with 3 distinct teeth; mesonotum dorsum with a thick layer of hairs, with scattered erect hairs. Queen: as in worker with modifications expected for caste. Male: 9-10 segmented antennae; parameres long and rectangular with many long erect hairs covering lateral surface; parameres often with distinct dorsolateral expansions. Compare with Acropyga keira and Acropyga romeo.

Workers are distinguishable from other species in the decedens species-group by the 8-9 antennal segments and the small head width (<0.52 mm). Worker mandibular dentition seems to be stable at 3 distinct teeth. However Bünzli (1935) reported observing 4 teeth and 7 antennal segments in A. paramaribensis (a junior synonym). Fortunately a large sample of this species was available for study, and I never observed a 4th mandibular tooth or 7 antennal segments among any specimens. Therefore, I suspect that Bünzli was in error or that the latter conditions are extremely rare abberations. He may have confused A. exsanguis with Acropyga smithii, which does have 4 mandibular teeth and can possess as few as 7 antennal segments. This species could be confused with Acropyga romeo, but can be separated from it based on the presence of a 4th smaller basal tooth.

Males of this species are distinct, with dorsolateral expansions of varying degrees found in the parameres (from slight lateral expansions to expansions that completely cover the digiti and cuspi in dorsal view). Variation in the dorsolateral expansion of the parameres at first led me to believe that there were several species present, but after examining multiple male specimens it is clear that the variation is a continuum and the specimens were indeed conspecific. Examination of the penis valves revealed that they are the same structural type regardless of the extent of the dorsolateral expansion.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Belize, Colombia, Costa Rica, Guatemala, Guyana, Honduras, Mexico, Panama, Suriname.

LaPolla (2004): This species has a wide distribution, ranging from central Mexico to northern Argentina.

Biology
Jack Longino: This species inhabits a variety of habitats including lowland rainforest, seasonal dry forest, and montane wet forest. It is most often encountered by looking under stones in moist areas or by sifting leaf litter from the forest floor (Winkler samples).

Twice during the wet season at La Selva Biological Station, 4-Nov-1991 and 22-Oct-1991, Longino observed massive mating swarms of males. While walking from the bridge to the dining hall at dusk, swirling clouds of males were forming above every small shrub in the grassy clearing around the station buildings. Even in the dining hall itself, small groups of males were forming aggregations above the white plates set out on the tables.

Even though Acropyga appear to be relatively rare ants when relying on common collecting methods such as manual search or litter sifting, the great clouds of flying males belie their true abundance in the habitat. Acropyga are entirely subterranean ants that live in the soil, a notoriously difficult microhabitat to sample.

Other Insects
LaPolla (2004) - A number of mealybugs have been recorded living with this species:, , , , , and. Trophophoretic behavior by queens has been observed on at least three separate occasions: queens carrying Rhizoecus coffeae (Bünzli, 1935; Roba, 1936; LaPolla, 2004) and Pseudorhizoecus sp. (Weber, 1957; LaPolla, 2004).

Nomenclature

 * . Rhizomyrma exsanguis Wheeler, W.M. 1909b: 238 (w.) MEXICO (Veracruz).
 * Combination in Acropyga (Rhizomyrma): Mann, 1922: 53.
 * Status as species: Mann, 1922: 53; Emery, 1925b: 29; Wheeler, W.M. 1935f: 327; Donisthorpe, 1936b: 110 (in list); Weber, 1944: 96 (redescription); Kempf, 1972a: 17; Bolton, 1995b: 57; LaPolla, 2004a: 47 (redescription); Branstetter & Sáenz, 2012: 255.
 * Senior synonym of bruchi: LaPolla, 2004a: 47.
 * Senior synonym of paramaribensis: LaPolla, 2004a: 47.
 * Senior synonym of robae: LaPolla, 2004a: 47.
 * Senior synonym of wheeleri: LaPolla, 2004a: 47.
 * bruchi. Acropyga (Rhizomyrma) bruchi Santschi, 1929d: 308 (w.) ARGENTINA (Santa Fe).
 * Status as species: Wheeler, W.M. 1935f: 327; Donisthorpe, 1936b: 110 (in list); Weber, 1944: 103 (redescription); Kempf, 1972a: 17; Bolton, 1995b: 57.
 * Junior synonym of exsanguis: LaPolla, 2004a: 47.
 * paramaribensis. Acropyga paramaribensis Borgmeier, 1933c: 263 (w.q.) SURINAME.
 * Borgmeier, 1934: 111 (m.); Bünzli, 1935: 519 (l.).
 * Combination in Acropyga (Rhizomyrma): Borgmeier, 1934: 109; Kempf, 1972a: 17.
 * Status as species: Borgmeier, 1934: 109 (redescription); Bünzli, 1935: 459 (redescription); Wheeler, W.M. 1935f: 327; Donisthorpe, 1936b: 110 (in list); Weber, 1944: 103 (redescription); Kempf, 1961b: 521; Kempf, 1972a: 17; Bolton, 1995b: 58.
 * Junior synonym of exsanguis: LaPolla, 2004a: 47.
 * robae. Acropyga (Rhizomyrma) robae Donisthorpe, 1936b: 108, figs. 1-3 (w.q.m.) COLOMBIA.
 * Status as species: Weber, 1944: 110 (redescription); Kempf, 1972a: 18; Bolton, 1995b: 58.
 * Junior synonym of exsanguis: LaPolla, 2004a: 47.
 * wheeleri. Acropyga (Rhizomyrma) wheeleri Mann, 1922: 52 (w.q.) HONDURAS.
 * Status as species: Emery, 1925b: 30; Wheeler, W.M. 1935f: 327; Donisthorpe, 1936b: 110 (in list); Weber, 1944: 101 (redescription); Kempf, 1972a: 18; Bolton, 1995b: 58.
 * Junior synonym of exsanguis: LaPolla, 2004a: 47.

Type Material
LaPolla (2004):
 * Rhizomyrma exsanguis W.M. Wheeler, 1909: 238 (w.). 3 syntype workers, MEXICO: Jalapa (F. Silvestri) (MCZC) [examined]. The designated lectotype is a worker labeled JSL TYPE # 118 and is deposited at MCZC. Lectotype is 1 of 3 specimens on the same card. The lectotype is the specimen to the right of the middle specimen if the card is oriented away from an examiner. The worker is raised up slightly off the card and the head is not glued down to the surface.
 * Acropyga (Rhizomyrma) wheeleri Mann, 1922: 52 (w.q.). 8 syntype workers, HONDURAS: Lombardia (Hugrich) (MCZC) (USNM) [examined].
 * Acropyga (Rhizomyrma) bruchi Santschi, 1929: 308 (w.). 3 syntype workers, ARGENTINA: Santa Fe, Rosario (NHMB) [examined].
 * Acropyga (Rhizomyrma) paramaribensis Borgmeier, 1933: 263 (w.q.). Syntype workers, syntype queens, SURINAM: Paramaribo (depository unknown) [not examined].
 * Acropyga (Rhizomyrma) robae Donisthorpe; 1936: 108 (w.q.m.). Holotype worker, COLOMBIA: La Esperanza (R. Roba) (BMNH) [examined]; 7 paratype workers, 5 paratype queens, 1 paratype male, same locality as holotype (BMNH) (MCZC) [examined].

Worker
LaPolla (2004) - (n=22): TL: 1.72-2.38; HW: 0.462-0.511; HL: 0.451-0.522; SL: 0.318-0.380; ML: 0.427-0.592; GL: 0.710-l.32; CI: 94.64-104.7; SI: 67.37-76.14.

Head: yellow; head about as broad as long; covered in a dense layer of appressed hairs, with scattered erect hairs toward posterior margin; posterior margin slightly concave medially; 8-9 segmented, incrassate antennae; apical segment about as long as preceding 4 segments; scape reaches or slightly fails posterior margin; clypeus with dense layer of erect hairs of varying lengths; mandible with 3 distinct teeth; gap exists between inner mandibular margin and anterior clypeal margin. Mesosoma: yellow; in lateral view, pronotum rises steeply toward mesonotum; pronotum with appressed hairs, erect hairs more posteriorly placed; mesonotum usually high and dorsally rounded, covered in dense layer of appressed hairs, with erect hairs scattered throughout; metanotal area distinct; propodeum below level of mesonotum, rounded with appressed and erect hairs; declivity steep. Gaster: petiole thick and erect; petiole reaches about midline of propodeal spiracle; gaster yellow; covered in a dense layer of appressed hairs, with scattered erect hairs throughout.

Queen
LaPolla (2004) - (n=5): TL: 2.17-3.48; HW: 0.52-0.547; HL: 0.508-0.547; SL: 0.367-0.443; SL: 0.367-0.443; ML: 0.828-0.963; GL: 1.14-l.97; CI: 100-107.28; SI: 67.34-82.96. As in worker, with modifications expected for caste and the following differences: scutellum with appressed and erect hairs; two longest hairs (almost as long as scutellum) anterolaterally placed opposite each other.

Male
LaPolla (2004) - (n=6): TL: l.87-2.41; HW: 0.346-0.412; HL: 0.388-0.410; SL: 0.267-0.311; ML: 0.67-0.785; GL: 0.79-1.28; CI: 89.18-105.93; SI: 67.65-75.49.

Head: brownish-yellow anteriorly becoming dark brown around 3 prominent ocelli; head about as broad as long; 9-10 segmented, incrassate antennae; apical segment about as long as preceding 3 segments; scape reaches or slightly surpasses posterior margin; clypeus with dense layer of appressed and erect hairs; mandible with 1-2 teeth; basal tooth, when present, small and indistinct, separated from apical tooth by wide diastema; gap exists between inner mandibular margin and anterior clypeal margin. Mesosoma: pronotum short and collar-like, overarched by mesonotum; anterior mesonotum broadly rounded; mesonotum dorsum flat, covered in a layer of largely short appressed hairs, with scattered longer appressed to erect hairs throughout; propodeum slightly rounded, with appressed hairs; declivity very short, but steep. Gaster: petiole thick and erect; gaster brownish-yellow, dorsum darker. Genitalia: in lateral view, parameres elongate and rectangular, covered in scattered sub erect to erect hairs; parameres with dorsolateral expansions apically, varying from completely covering to only slightly covering digiti and cuspi in dorsal view; cuspi cylindrical, curved apically toward digiti; apices of cuspi with short, peg-like teeth; digiti anvil-shaped apically, meeting cuspi on dorsal surface, where short, peg-like teeth are present.

References based on Global Ant Biodiversity Informatics

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