Acropyga guianensis

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Acropyga guianensis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. guianensis
Binomial name
Acropyga guianensis
Weber, 1944

Acropyga guianensis casent0249920 p 1 high.jpg

Acropyga guianensis casent0249920 d 1 high.jpg

Specimen Labels

Evolutionary Relationships
Acropyga



Acropyga ayanganna




Acropyga donisthorpei



Acropyga panamensis







Acropyga guianensis



Acropyga stenotes






Acropyga fuhrmanni



Acropyga smithii





Acropyga romeo




Acropyga hirsutula




Acropyga dubitata




Acropyga decedens, Acropyga goeldii



Acropyga epedana












Acropyga arnoldi



Acropyga silvestrii






Acropyga kinomurai



Acropyga lauta





Acropyga sauteri




Acropyga acutiventris




Acropyga myops




Acropyga butteli




Acropyga ambigua



Acropyga pallida










Based on Blaimer et al., 2016. Note only selected Acropyga species are included, and undescribed species are excluded.

Specimens have been collected from the leaf litter in rainforest but otherwise nothing is known about the biology of Acropyga guianensis.

Identification

LaPolla (2004) - Worker: 10-11 segmented antennae; head distinctly longer than broad; mandible with 4-5 teeth, a distinct diastema between 3rd and 4th tooth; dorsum of mesosoma rounded in lateral view, with a layer of appressed hairs underneath several prominent erect hairs. Queen: as in worker with modifications expected for caste. Male: unknown. Compare with larger species of the goeldii complex, Acropyga ayanganna, and Acropyga decedens.

At first examination it is possible to confuse the worker of A. guianensis with some members of the goeldii complex of species. Upon closer inspection, however, it is fairly easy to distinguish this species with its head longer than broad and a distinctive mandibular dentition: 4 teeth with basal tooth separated by a diastema, or 5 teeth with a small tooth in the diastema region. The mesosoma is useful for identification as well, with mesosomal shape and the placement of dorsal hairs being diagnostic. Additionally, the clypeus is broad and lacks a dense covering of erect hairs, which are commonly observed many goeldii complex species.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Bolivia, Brazil, Colombia, Ecuador, Guyana (type locality).

LaPolla (2004): This species has a large range, having been collected from northern South America south into Bolivia.

Check distribution from AntMaps.

Distribution based on specimens

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The above specimen data are provided by AntWeb. Please see Acropyga guianensis for further details

Biology

Little is known about Acropyga guianensis. Until further studies reveal more about this species we can infer that its natural history and biology should be similar to other Acropyga. LaPolla published a worldwide revision of the Acropyga in 2004 and the following synopsis is based on this excellent treatment of the genus.

In overall appearance Acropyga are small, robust, yellowish ants possessing a thin, easily collapsible cuticle. The species generally appear rather similar to each other morphologically. In some species workers and queens display an unusual range of phenotypic variation. Antennal segment number, for example, can vary within and between species. Even a single specimen may posses antennae with a different number of antennal segments and workers in numerous species possess one more antennal segment than conspecific males.

The small eyes, reduced antennae segmentation, lightly pigmented cuticle, and hairs covering the cuticle of Acropyga species are suggestive of a completely subterranean existence. Species also display photophobic behavior (Weber, 1944; LaPolla et al., 2002). Acropyga can survive in a wide range of habitats, from deserts to rainforests, though they do not seem able to survive in regions where temperatures below freezing persist for several months at a time. Some species, such as Acropyga pallida and Acropyga silvestrii for example, are found within a very wide range of habitats. Undoubtedly, the Acropyga lifestyle of existing below the surface buffers them against extremes of the outside environment.

Acropyga nests are found in leaf litter, under stones, in rotten wood (lying on or near the soil surface) and in the soil. Observations of nests of various species show the nests are large, consisting of at least several thousand individuals. The nest structure is diffuse with apparently no central nesting location (LaPolla et al., 2002). Tunnels and indistinct chambers stretch out over large areas through the nesting medium. Polygyny has been suggested for several species. The origins of polygyny remains uncertain, but two routes are suggested based on field observations. Biinzli (1935) found both the occurrence of pleometrosis (founding of a colony by multiple queens) and the acquisition of young queens by established colonies in Acropyga exsanguis.

All Acropyga are thought to be hypogaeic (living entirely underground), surviving primarily by "tending" mealybugs (Hemiptera: Pseudococcidae) on underground roots for their exudate (sometimes referred to as "honeydew") (Weber, 1944; Williams, 1998). This mutually beneficial relationship is called trophobiosis (Holldobler and Wilson, 1990).

Acropyga species are all believed to be obligate coccidophiles (dependent on their tended mealybugs for survival). The strength of this trophophitic relationship is clarified by a number of observations. Queens of eleven species have been observed emerging from their nests prior to their mating flight with a mealybug held in their mandibles (Biinzli, 1935; Wheeler, 1935b; Brown, 1945; Eberhard, 1978; Prins, 1982; Buschinger et al., 1987; Williams, 1998; Johnson et al., 2001). The mealybug that each queen carries presumably serves as a "seed individual" from which a new generation of mealybugs will be started in the newly founded ant colony (Weber, 1944; Williams, 1998). This behavior is called trophophoresy (LaPolla et al. 2002) with queens exhibiting this behavior said to be trophophoretic. The mealybugs utilized by Acropyga belong to the subfamily Rhizoecinae, and it is likely that the mealybugs are not able to survive independently of the ants (Williams, 1998). LaPolla et al. (2002) observed that Acropyga epedana keeps mealybugs with their brood. When a nest in captivity was starved, workers refused a variety of food items presented to them, suggestiving that the ants are completely dependent on the mealybugs as a food source. Fossil evidence suggests that the trophobiotic behavior ofAcropyga ants is an ancient one. Johnson et al. (2001) reported that Acropyga queens were discovered in Dominican amber, either holding a mealybug or with a mealybug nearby in the amber matrix. The amber was dated to the Miocene and is at least 15-20 million years old.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • guianensis. Acropyga (Rhizomyrma) guianensis Weber, 1944: 120, fig. 1 (w.) GUYANA. LaPolla, 2004a: 76 (q.).

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

LaPolla (2004) - The lack of a worker-associated male specimen for this species makes its placement within the genus problematic and it therefore remains unplaced in a species-group. Despite its initial appearance to the contrary, I do not think this species belongs in the decedens species-group, for its mandibles, clypeus and mesosomal characters (see above for contrasts) do not suggest placement in that group. The narrow-headed Acropyga stenotes is possibly closely related to A. guianensis based on similar mesosomal characteristics (see A. stenotes discussion section for more details). Once males are discovered for this species a more precise phylogenetic placement will be possible.

Description

Worker

LaPolla (2004) - (n=10): TL: 1.83-2.4; HW: 0.472-0.532; HL: 0.508-0.609; SL: 0.408-0.5; ML: 0.488-0.682; GL: 0.693-1.09; CI: 84.24-95.36; SI: 84.50-96.08.

Head: brownish-yellow; head distinctly longer than broad; covered in appressed hairs; posterior margin entire to slightly concave; suberect to erect hairs often at posterolateral corners; 10-11 segmented, incrassate antennae; scape typically surpasses posterior margin by about the length of the pedicel; clypeus convex medially, surface with numerous long erect hairs; mandible usually with 4 teeth; 4th tooth separated by a short diastema; a smaller tooth can sometimes be found in the diastema region separating the 4th and basal teeth, making the mandible effectively 5-toothed. Mesosoma: brownish-yellow; in lateral view, pronotum rises steeply toward mesonotum; posteriorly pronotum with many long erect hairs; mesonotum with many longer erect hairs and thick layer of appressed hairs underneath; propodeum slightly below layer of mesonotum; mesosomal dorsum rounded from posterior portion of pronotum through the propodeum; declivity steep. Gaster: petiole thick and erect; gaster brownish-yellow; covered with a thick layer of appressed hairs, with many scattered erect hairs throughout, giving gaster a spiky appearance, especially toward posterior end.

Queen

LaPolla (2004) - (n=3): TL: 3.48-3.65; HW: 0.631-0.64; HL: 0.696-0.7; SL: 0.612-0.636; ML: 1.07-1.18; GL: 1.87-1.77; CI: 90.29-91.82; SI: 96.84-100.79.

As in worker except for modifications expected with caste, and with the following differences: overall much darker than worker, becoming brown dorsally in many specimens; mesonotum flat, with abundant suberect to erect hairs and a dense layer of appressed hairs; scutellum with many erect hairs; propodeum low.

Male

Males are not known for this species.

Type Material

Acropyga (Rhizomyrma) guianensis Weber, 1944: 120 (w.). 3 syntype workers, GUYANA: HMPS, Mazaruni River (N.A. Weber) (MCZC) [examined]. The designated lectotype is a worker on the same point as one of the paralectotypes; the lectotype is the specimen raised up slightly off of the point, and is labeled JSL TYPE # 124. The second paralectotype, on another point, has another Acropyga specimen next to it that is clearly not A. guianensis (probably Acropyga smithii), so it is not a paralectotype of this species.

References