Acropyga gelasis

AntWiki - Where Ant Biologists Share Their Knowledge
Jump to: navigation, search
Acropyga gelasis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. gelasis
Binomial name
Acropyga gelasis
LaPolla, 2004

Acropyga gelasis casent0903177 p 1 high.jpg

Acropyga gelasis casent0903177 d 1 high.jpg

Specimen Labels

This species is only known from its type locality.

Identification

LaPolla (2004) - Worker: 11 segmented antennae; head and mesosoma brownish-yellow, gaster darker; clypeus broad, with distinct beak-like tip medially; median portion of head and posterior margin with many erect hairs; appressed hairs on head sparse, none on mesosomal dorsum. Queen: unknown. Male: unknown. Compare with Acropyga hystrix.

With a unique "beak-like" medial portion of the anterior clypeal margin, A. gelasis is fairly easy to separate from other species. The structure of the anterior clypeal margin, "the beak", is similar to that of the butteli species-group, though it seems to be a result of convergence rather than indicative of a close relationship. Overall, this species, along with Acropyga hystrix, is darker (brownish-yellow) and with less pilosity than other Acropyga species.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Indonesia (type locality).

Check distribution from AntMaps.

Loading map...

Check specimen data from AntWeb

Biology

Little is known about Acropyga gelasis. 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

Known only from the worker caste.

Nomenclature

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

  • gelasis. Acropyga gelasis LaPolla, 2004a: 62, figs. 25, 46 (w.) INDONESIA (Banggai Archipelago).

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

LaPolla (2004) - The species' placement within the myops species-group is based on the fact that A. gelasis possesses widely separated torulae and mandibles that appear similar to Acropyga myops. Worker morphology suggests A. gelasis is closely related to Acropyga hystrix.

Description

Worker

(n=5): TL: 2.09-2.31; HW: 0.528-0.538; HL: 0.557-0.599; SL: 0.406-0.432; ML: 0.59-0.687; GL: 0.921-1.09; CI: 88.31-96.59; SI: 76.75-81.05.

Head: brownish-yellow, darker toward apex; head longer than broad; posterior margin concave medially; short erect hairs scattered from median portion of head and along posterior margin; 11 segmented, incrassate antennae; scape reaches to nearly reaches (approximately 1/3 length of pedicel) to posterior margin; scape with short erect hairs toward apical end; clypeus broad, convex medially; median portion of anterior clypeal margin projects forward, giving it distinct "beak-like" appearance in full frontal view; mandible with 6 teeth; 3rd tooth from apical often smaller than others; inner mandibular margin uneven. Mesosoma: brownish-yellow; in lateral view, pronotum rises steeply toward mesonotum; pronotum with short erect hairs anteriorly and longer erect hairs posteriorly; mesonotum rounded, with many short and longer erect hairs dorsally; mesonotum slightly higher than propodeum; metanotal area distinct; propodeal dorsum flat, rounding into steep declivity. Gaster: petiole thick and erect, reaching height of upper portion of propodeal spiracle; gaster dark brownish-yellow; with a layer of appressed hairs, scattered longer, erect hairs throughout.

Type Material

Holotype worker, INDONESIA: Banggai Arch., Potil Kecil, I 28'S, 123 34' E (M.J.D. Brendell) (The Natural History Museum); 14 paratype workers (BMNH) (Museum of Comparative Zoology). The holotype is labeled JSL TYPE #109.

Etymology

The specific epithet gelasis is Greek for to laugh, alluding to the odd looking medial point of the anterior clypeal margin.

References