Acropyga ayanganna

This ant is only known from Mt. Ayanganna in Guyana.

Identification
LaPolla (2004) - Worker: 10 segmented antennae; eyes relatively large; mandible with 4 distinct teeth, and a smaller tooth between 2nd and 3rd teeth; scape surpasses posterior margin by about length of pedicel. Queen: As in worker with modifications expected for caste. Male: 11 segmented antennae; caudally parameres taper to a point; cuspi much shorter than digiti; mandible with 3 distinct teeth and occasionally smaller teeth between apical and 2nd or between 2nd and 3rd teeth. Compare with Acropyga fuhrmanni and Acropyga guianensis.

The worker caste of A. ayanganna closely resembles Acropyga fuhrmanni in overall appearance. Several key features separate workers of the two species, however. Among those characters are the 10 segmented antennae and 5 mandibular teeth of A. ayanganna. A. fuhrmanni is known only from specimens with 8 segmented antennae and 4 mandibular teeth. The greatest similarity is in the head, where both species possess relatively large eyes that are close to the anterior margin of the head. Despite the similarity of the worker caste between A. ayaganna and A. fuhrmanni, they are not closely related. The sister species to A. ayanganna is Acropyga panamensis. This is interesting because based solely on overall worker morphology, they appear very distantly related to each other. However, the males of these two species reveal their close relationship by the presence of similar cuspi and digiti, parameres and penis valves, all of which serve as synapomorphies. The differences observed in the worker morphology between A. ayanganna and A. panamenis underscores the importance of examining males to determine phylogenetic relationships, and not relying strictly upon worker morphology.

Key to New World Acropyga Workers / Queens / Males

Distribution based on Regional Taxon Lists
Neotropical Region: Guyana.

This species is known only from Mount Ayanganna in Guyana.

Biology
La Polla (2004): Acropyga ayanganna forms large nests, with many thousands of workers. Some nests were found along a stream bank in sandy soil, under rocks and root mats. Other nests were found in the surrounding forest under stones and in rotten logs. This species was very abundant at the type locality. Many nests were located and it was often difficult to distinguish where one colony ended, and another began. Several dealate queens were collected along with workers, which suggests the species is polygynous.

The physical structure of the nests was diffuse (no obvious central nesting area), like many other Acropyga species in which nesting habits are known, with many tunnels and chambers where brood and mealybugs were kept. The distinctness of the chambers however stands in contrast to observations of several other Acropyga species, which construct chambers that appear to be little more than slight expansions of tunnels (LaPolla et. al, 2002). When a number of A. ayanganna workers, brood and mealybugs were collected and placed in a petri dish overnight, the ants gathered their brood and mealybugs and placed them into a distinct chamber they constructed from loose dirt in the petri dish, supporting the observation that this species constructs well-defined chambers. Furthermore, mealybugs and brood were kept together in a mixed pile.

Nomenclature

 *  ayanganna. Acropyga ayanganna LaPolla, 2004a: 71, figs. 28, 43, 46 (w.q.m.) GUYANA.

Worker
Head: yellow; covered in a dense layer of appressed hairs; head about as long as broad; posterior margin slightly concave; several erect hairs found at posterolateral corners; eyes relatively large, placed at lower 1/4 side of head; 10 segmented, incrassate antennae; scape surpasses posterior margin by about length of pedicel; scape with many erect hairs scattered throughout; clypeus covered in dense layer of erect hairs; medially clypeus strongly convex; mandible with 4 distinct teeth; a smaller tooth often present between the 2nd and 3rd larger teeth (from apical) making mandible 5-toothed; a short diastema present between 3rd and 4th larger teeth; a gap exist between inner mandibular margin and anterior clypeal margin. Mesosoma: yellow; in lateral view pronotum rises steeply toward mesonotum; covered in layer of appressed hairs, some of them long; pronotum with several, long erect hairs posteriorly; mesonotum with a layer of appressed hairs, several longer erect hairs throughout; mesonotum much higher than propodeum; metanotal area distinct; propodeum with appressed hairs; declivity steep. Gaster: petiole thick and erect reaching base of propodeal spiracle; gaster yellow; covered in thick layer of appressed hairs, with scattered erect hairs thoughout.

Measurements (n=4): TL: 2.28-2.57; HW: 0.598-0.649; HL: 0.591-0.648; SL: 0.483-0.566; ML: 0.665-0.726; GL: 1.02-1.22; CI: 100.15-103.32; SI: 77.53-89.27.

Queen
As in worker with modifications expected for caste.

Measurements (n=1): TL: 3.88; HW: 0.864; HL: 0.830; SL: 0.762; ML: 1.31; GL: 1.74; CI: 88.19; SI: 104.09.

Male
Head: yellowish-brown, darker toward apex around 3 prominent ocelli; head broader than long, becoming narrower toward apex; covered in layer of appressed hairs; posterior margin with several erect hairs; 11 segmented, slightly incrassate antennae; apical segment about as long as proceeding 3 segments; scape surpasses posterior margin by about length of first two funicular segments; clypeus narrow, covered in layer of erect hairs; clypeus slightly convex medially; mandible with 3 distinct teeth; a smaller tooth can sometimes be found between the larger apical and 2nd and/or between 2nd and 3rd teeth, effectively making mandible 4-toothed; a gap exist between inner mandibular margin and anterior clypeal margin. Mesosoma: brownish-yellow; pronotum short and collar-like, overarched by mesonotum; anterior mesonotum broadly rounded; dorsum of mesonotum flat, covered in layer of largely short appressed hairs, with scattered longer appressed to erect hairs throughout; propodeum slightly rounded, with appressed hairs; declivity steep. Gaster: petiole, thick and erect; gaster brownish-yellow, dorsum darker. Genitalia: in lateral view parameres taper to a point at apices; covered with many erect hairs, with many longer hairs posteriorly; volsellar lobes with many short, erect hairs; cuspi short and rounded, with peg-like teeth at apex, not reaching digiti; digiti large, rounded at apices; peg-like teeth on side facing cuspi; digiti much longer than cuspi.

Measurements (n=2): TL: 2.47-2.56; HW: 0.505-0.528; HL: 0.46-0.485; SL: 0.452-0.462; ML: 0.921-0.96; GL: 1.09- 1.11; CI: 108.87-109.78; SI: 85.61-91.49.

Type Material
Holotype worker, GUYANA: Mt. Ayanganna; Falls Camp; 5º 22.332' N, 59º 57.563' W; elev. ca. 1134 m, (J.S. LaPolla et al.) (#JSL 021012-10) (UGBC); 9 paratype workers, 1 paratype queen, 5 paratype males,. The holotype is labeled JSL TYPE # 120.

Etymology
The specific epithet ayanganna refers to Mount Ayanganna, a remote peak in the Pakaraima Mountains in western Guyana, and is the locality where this species was discovered.