Acropyga bakwele

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Acropyga bakwele
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. bakwele
Binomial name
Acropyga bakwele
LaPolla & Fisher, 2005

Acropyga bakwele casent0104123 dorsal 1.jpg

Acropyga bakwele casent0104123 profile 1.jpg

Specimen Label

Only known from the type material, collected from leaf litter in rainforest.

Identification

LaPolla and Fisher (2005) - 8-toothed mandible; mandibular apical tooth about twice as along as other teeth; median ocellus present; total length > 3 mm.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Gabon (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about Acropyga bakwele. 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

Queens and Males of the species are unknown.

Worker

Nomenclature

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

  • bakwele. Acropyga bakwele LaPolla & Fisher, 2005: 602, figs. 1-4 (w.) GABON.

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

Description

Worker

(Holotype worker) TL: 3.24; HL: 0.902; HW: 0.870; SL: 0.751; ML:1.069; GL: 1.272; CI: 96.45; SI: 86.32.

Overall appearance similar to Acropyga arnoldi and Acropyga silvestrii, see LaPolla (2004) for details of these two species. Head: reddish-yellow; head slightly longer than wide; covered in a thick layer of appressed hairs, with short erect hairs along posterior margin; posterior margin slightly concave medially; median ocellus present; eyes relatively large for an Acropyga (ca. 10 facets) and placed at lower ¼ of head; 11-segmented, incrassate antennae; scape surpasses posterior margin by about half length of pedicel; scape with thick layer of appressed hairs, scattered erect hairs throughout; clypeus slightly convex medially; mandible broad, with six distinct teeth; mandibular basal angle distinct, but not forming seventh tooth; apical tooth twice as long as other teeth. Mesosoma: reddish-yellow; in lateral view, pronotum with short anterior shelf; dorsum covered in layer of appressed hairs, with scattered erect to suberect hairs throughout; metanotal area distinct; propodeum rounded; declivity steep. Gaster: petiole think and erect, with erect hairs; gaster reddish-yellow, with thick layer of appressed hairs and scattered erect to suberect hairs throughout.

Etymology

The species epithet, bakwele, is in honor of the Bakwele pygmies who assisted BLF during his fieldwork in Gabon.

References

LaPolla, J.S. and Fisher, B.L. 2005. A remarkable new species of Acropyga from Gabon, with a key to the Afrotropical species. Proceedings of the California Academy of Sciences. 56(4):601-605. PDF (page 602, figs. 1-4 worker described)