Acropyga goeldii

A relatively common species with workers that are morphologically variable across the wide range of the species.

Identification
From Lapolla (2004):

Diagnosis - Worker: 9-11 segmented antennae; scape reaches or surpasses posterior margin; 3-4 teeth on mandible; head as broad or broader than long; clypeus with abundant erect hairs. Queen: as in worker with modifications expected for caste. Male: 12 segmented antennae; parameres rectangular and thin with apex wider reaching a sharp dorsocaudal point. Compare with Acropyga palaga and other members of the goeldii complex, Acropyga decedens, and Acropyga guianensis .

The species boundary of A. goeldii was difficult to ascertain, and there is still some degree of uncertainty surrounding this species and its immediate relatives. The difficulty arises from the fact that workers within the goeldii complex are very difficult to distinguish from each other. A. goeldii workers are virtually indistinguishable from Acropyga palaga (see A. palaga for further discussion), but additionally, Acropyga epedana, Acropyga keira, and Acropyga exsanguis all present difficulties in identification from one another. Listed are characters that can provide some diagnostic help in identifying this species; comments in parentheses are for A. goeldii. From: A. exsanguis (usually wider head, more antennal segments and larger in total length), A. keira (many more erect hairs on mesosoma), A. epedana (more erect hairs on mesosoma and longer, wider head).

Since A. goeldii is such a variable species, the worker caste is unreliable for diagnostic purposes. Worker specimens have been observed, for instance, with a range of mandibular teeth from 3 well-defined teeth, 3 well defined teeth and a smaller more offset basal tooth, to 4 well defined teeth. Additionally, the mesonotal dorsum has been observed to be at the same height as the propodeum in some specimens, but in other specimens the mesonotum rises well above the level of the propodeum. The shape of the worker head is variable as first observed by Bünzli (1935). At this time however I do not believe that the variation observed warrants separate species recognition.

Key to New World Acropyga Workers / Queens / Males

Distribution based on Regional Taxon Lists
Neotropical Region: Barbados, Brazil, Colombia, Costa Rica, Greater Antilles, Guyana, Panama, Paraguay, Suriname, Trinidad and Tobago, Venezuela.

From LaPolla (2004): This species has a wide range across tropical South America, and has been recorded occurring as far north as Barbados and Costa Rica. It is found in Suriname, Panama, Trinidad and Tobago, Paraguay and Colombia.

Biology
LaPolla (2004): Acropyga goeldii is a known trophophoretic species and is associated with at least 4 mealybug species: Capitisetella migrans, Dysmicoccus radicis, Neochavesia sp., and R. coffeae.

Weber (1944) reported this species was found "tending the common Trinidad type of coccids on rootlets of small plants which were interwoven into the husk of a brazil nut fruit lying on the ground. Under the husk was yellow sandy clay soil in which the ants had tunnels." He also reported trying to feed a small nest series he placed in a glass container to observe them while they were alive and found they did not eat pieces of fruit offered to them. As in Acropyga epedana (LaPolla et al., 2002) this species apparently only fed on honeydew produced by the mealybugs, and the nest died within a month (mealybugs were present, but they had no roots to feed on). He did not report if any of the mealybugs had been eaten by the ants, and interestingly carnivory in "starving" nests has not been reported.

This is most likely the species Eberhard (1978) reported as being trophophoretic (identified from specimens deposited at MCZC). He observed several mating swarms of males and females, each consisting of several dozen individuals. The swarms seemed to be either predominantly male or predominantly female. Eberhard (1978) observed that the emergence of reproductives occurs in the day after a recent rainfall and that they come out of the nest through small holes (in this case in a grass lawn). Around the holes several workers were observed on the surface, and this is perhaps the only time that Acropyga workers emerge from their nests to the surface. Predation of alate queens that had recently emerged from nests by the ponerine ant, Ectatomma ruidum was also observed.

Nomenclature

 *  goeldii. Acropyga (Rhizomyrma) goeldii Forel, 1893g: 348 (footnote) (w.) BRAZIL. Combination in Rhizomyrma: Forel, 1912i: 60; in Acropyga (Rhizomyrma): Emery, 1925b: 29. Junior synonym of decedens: Costa Lima, 1931: 7. Revived from synonymy: Wheeler, W.M. 1935f: 322; Weber, 1944: 93. Senior synonym of borgmeieri, columbica, marshalli, pachycera, pickeli, quadriceps, rutgersi, tridentata, trinitatis: LaPolla, 2004a: 49.
 * pachycera. Rhizomyrma pachycera Emery, 1906c: 182 (w.q.) PARAGUAY. Combination in Acropyga (Rhizomyrma): Emery, 1925b: 30. Junior synonym of goeldii: LaPolla, 2004a: 49.
 * columbica. Rhizomyrma goeldii var. columbica Forel, 1912i: 61 (w.) COLOMBIA. Combination in Acropyga (Rhizomyrma): Emery, 1925b: 29. Junior synonym of goeldii: LaPolla, 2004a: 49.
 * tridentata. Rhizomyrma goeldii var. tridentata Forel, 1912i: 61 (q.m.) PANAMA. Combination in Acropyga (Rhizomyrma): Emery, 1925b: 29. Junior synonym of goeldii: LaPolla, 2004a: 49.
 * marshalli. Rhizomyrma marshalli Crawley, 1921: 93, fig. 2 (w.) BARBADOS. Combination in Acropyga (Rhizomyrma): Emery, 1925b: 30. Junior synonym of goeldii: LaPolla, 2004a: 49.
 * pickeli. Acropyga (Rhizomyrma) pickeli Borgmeier, 1927a: 287, figs. 1, 2 (w.q.) BRAZIL. Weber, 1944: 102 (m.). Junior synonym of decedens: Costa Lima, 1931: 7. Revived from synonymy: Borgmeier, 1932a: 238. Junior synonym of goeldii: LaPolla, 2004a: 50. See also: Wheeler, W.M. 1935f: 322; Weber, 1944: 102.
 * rutgersi. Acropyga (Rhizomyrma) rutgersi Bünzli, 1935: 464, figs. 8-11, 12, 14-16, 18, 20, 24 (w.q.m.) SURINAM. Junior synonym of goeldii: LaPolla, 2004a: 50.
 * borgmeieri. Acropyga (Rhizomyrma) borgmeieri Donisthorpe, 1939c: 153 (m.) GUYANA. Junior synonym of goeldii: LaPolla, 2004a: 50.
 * quadriceps. Acropyga (Rhizomyrma) quadriceps Weber, 1944: 113, fig. 5 (w.) TRINIDAD. Junior synonym of goeldii: LaPolla, 2004a: 50.
 * trinitatis. Acropyga (Rhizomyrma) trinitatis Weber, 1944: 117, figs. 7, 8, 17-19 (w.q.) TRINIDAD. Junior synonym of goeldii: LaPolla, 2004a: 50.

LaPolla (2004) - The taxonomy as presented of the decedens species-group relies heavily on male morphology, but males are scarce in collections, thereby making assessment of male variation among and between species difficult. Hence, I have been hesitant to "split" some of the variation observed in workers of this species as separate species. Males have proven exceedingly useful in the ascertaining of most species boundaries in the decedens species-group. However, even males for A. goeldii are, like the workers, morphologically variable. The defining characteristics are found in the penis valve structures. In A. goeldii penis valves possess a rounded ventral extension and the dorsal margin of the penis valves bulge out slightly toward the apodeme. The ventral aspect of the penis valves are also unique to the species. In contrast, the parameres vary considerably and look similar to A. palaga, in that the width of the parameres does not vary much across its length, or they can become narrower caudally from the base and become wide again near the caudal ends. Specimens in which parameres resembled A. palaga but the penis valves fit the A. goeldii type for now are regarded as A. goeldii. Nonetheless, as more worker-associated male specimens of this species become available its status should be reevaluated, because it would not be surprising if there are several species (some of which mayor may not be closely related) "hidden" under what is presently known as A. goeldii. For instance, the workers of Acropyga decedens are difficult to distinguish from A. goeldii, and the latter was even synonymized with A. decedens by Costa Lima (1931). However, despite the morphological similarity of workers, A. decedens and A. goeldii are clearly not closely related once male morphology is compared.

Worker
From LaPolla (2004) - Head: yellow; head about as broad as long; posterior margin slightly concave to entire; covered in a layer of appressed hairs, with several erect hairs usually along posterior margin; 9-11 segmented, incrassate antennae; scapes reaches or slightly surpasses (less than half length of pedicel) posterior margin; clypeus narrow, convex, covered in abundant erect hairs; mandible with variable numbers of teeth; with 4 distinct teeth, 3 distinct teeth and a minute basal tooth, or only 3 distinct teeth with no evidence of a 4th tooth; 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; posteriorly pronotum with many erect hairs; mesonotum covered in a thick layer of appressed hairs, with many scattered erect hairs; mesonotum higher than propodeum; metanotal area often distinct, with one or two sulci present; propodeum rounded with thick layer of appressed hairs, and scattered erect 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.

Measurements (n=12): TL: 2.03-2.57; HW: 0.524-0.623; HL: 0.503-0.616; SL: 0.398-0.473; ML: 0.554-0.714; GL: 0.723-1.32; CI: 94.78-110.81; SI: 64.91-78.63.

Queen
From LaPolla (2004) - As in worker with modifications expected for caste and the following differences: mesosoma with many short, erect hairs.

Measurements (n=2): TL: 3.19-3.21; HW: 0.652-0.669; HL: 0.568-0.613; SL: 0.475-0.529; ML: 1.02-l.05; GL: 1.55-1.6; CI: 109.14-114.79; SI: 72.85-79.07.

Male
From LaPolla (2004) - Head: brown to yellowish-brown, darker at apex around 3 prominent ocelli; head broader than long, though anteriorly, narrowing giving head a roughly triangular appearance; covered in a layer of appressed to erect hairs; eyes large, breaking outline of head in full frontal view; 12 segmented, slightly incrassate antennae, the apical segment about as long as proceeding 2-3 segments; scape surpasses posterior margin by about length of pedicel; clypeus convex medially, covered in thick layer of erect hairs; mandible with 2-3 distinct teeth; when with 2 teeth a wide diastema separates apical and basal tooth; 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 a layer of short appressed to erect hairs; scutellum roughly oval-shaped, covered in longer erect hairs; propodeum rounded into short, steep declivity. Gaster: petiole thick and erect; gaster brownish-yellow, covered in layer of appressed hairs, with scattered erect hairs throughout. Genitalia: in lateral view, parameres long, rectangular, with scattered erect to suberect hairs; shape of parameres variable from thin but expanded at apex to a sharp dorsal point and slightly wider ventral aspect, to thick throughout length and square at apex; cuspis cylindrical; digitus with apices anvil-shaped; digitus meets cuspis dorsally, where both have structures have a series of short, peg-like teeth.

Measurements (n=5): TL: 2.38-2.51; HW: 0.448-0.461; HL: 0.439-0.453; SL: 0.346-0.403; ML: 0.833-0.986; GL: 0.98-1.18; CI: 100-102.9; SI: 76.89-87.42.

Type Material
Acropyga (Rhizomyrma) goeldii Forel, 1893: 348 (w.). 3 syntype workers, BRAZIL: Parahyba, Provo Rio de Janeiro (Goeldi) (MHNG) (AMNH) [examined]. The designated lectotype is a worker specimen labeled JSL TYPE # 108 and is deposited at MHNG. Fore1 1912b: 60, first combination in Rhizomyrma; Emery, 1925: 29, first combination in Acropyga; Costa Lima 1931: 7, junior synonym of Acropyga decedens; W.M. Wheeler, 1935b: 322, revived from synonymy; Weber 1944: 93, description and key.

Rhizomyrma pachycera Emery, 1906: 182 (w.q.). Syntype worker, syntype queen. PARAGUAY: Tacuru Pucu (MCSN) [examined]. Emery, 1925: 29, first combination in Acropyga; Weber, 1944: 95, description and key. NEW SYNONYM.

Rhizomyrma goeldii columbica Forel, 1912b: 61 (w.). Holotype worker, COLOMBIA (no specific locality given) (MHNG) [examined]. NEW SYNONYM. Emery, 1925: 29, first combination in Acropyga; Weber, 1944: 94, description and key.

Rhizomyrma goeldii tridentata Forel, 1912b: 61 (q.m.). 3 syntype males, 3 syntype queens, PANAMA (no specific locality given) (Christopherson) (MHNG) [examined]. Emery, 1925: 29, first combination in Acropyga; Weber, 1944: 94, description and key. NEW SYNONYM.

Rhizomyrma marshalli Crawley, 1921: 93 (w.). Holotype worker, BARBADOS: B.W.I. (J.R. Bovell) (BMNH) [examined]. NEW SYNONYM. Emery, 1925: 30, first combination in Acropyga; Weber, 1944: 101, description and key.

Acropyga (Rhizomyrma) pickeli Borgmeier, 1927: 287 (w.q.). Syntype workers, 2 syntype queens, BRAZIL: Parahyba do Norte (MCZC, queens only; depository for workers unknown) [examined queens only]. NEW SYNONYM. Costa Lima, 1931: 7, junior-synonym of A. decedens; Borgmeier, 1932: 238, revived from synonymy; W.M. Wheeler, 1935b: 322, listed; Weber, 1944: 102, description and key.

Acropyga (Rhizomyrma) rutgersi Bünzli 1935: 464 (w.q.m.). Syntype workers, syntype queens, syntype males, SURINAM: Paramaribo (depository unknown) [not examined]. NEW SYNONYM. Weber, 1944: 104, description and key.

Acropyga (Rhizomyrma) borgmeieri Donisthorpe, 1939: 153 (m.). Holotype male, GUYANA: Forest Settlement, Mazaruni River (BMNH) [examined]. NEW SYNONYM. Weber, 1944: 111, description and key.

Acropyga (Rhizomyrma) quadriceps Weber, 1944: 113 (w.). 4 syntype workers, TRINIDAD: Maracas Valley, B.W.L (N.A. Weber) (MCZC) [examined]. NEW SYNONYM.

Acropyga (Rhizomyrma) trinitatis Weber, 1944: 117 (w.q.). 4 syntype workers, 1 syntype queen, TRINIDAD: between 10-12th mile of Arima-Blanchisseuse Road (N.A. Weber) (MCZC) [examined]. NEW SYNONYM.