Acropyga keira

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Acropyga keira
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. keira
Binomial name
Acropyga keira
LaPolla, 2004

Acropyga keira casent0619182 p 1 high.jpg

Acropyga keira casent0619182 d 1 high.jpg

Specimen Labels

Workers and males were collected from a nest in July, but otherwise nothing is known of its natural history.

Identification

Lapolla (2004) - Worker: 9 segmented antennae (but see description); mesosoma with short, appressed hairs, giving it a bare appearance; mandible with 3 teeth. Queen: unknown. Male: 11 segmented antennae; parameres roughly rectangular, covered in hairs of varying lengths, with thickest concentration toward the middle. Compare with Acropyga exsanguis and Acropyga romeo.

The short appressed hairs that cover A. keira are the main distinguishing characteristic of the worker. Nonetheless, A. keira workers can be difficult to distinguish from other members of the goeldii complex, especially from Acropyga exsanguis workers. A. keira has very few erect to suberect hairs on the mesosoma, and when present they are only found on the posterior region of the pronotum, whereas A. exsanguis always has abundant erect to suberect hairs on the mesosoma. The head of A. keira is also typically longer than broad, while in A. exsanguis the head is typically broader or at least as broad as long.

The best way to confirm A. keira is with male specimens, which are very distinct from A. exsanguis and other closely related species. The penis valve of A. keira is unique in that it is shorter (as measured from apodeme to caudal tip) than other goeldii complex members, and the laterally expanded, flattened tips are distinctly large relative to the whole structure.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Costa Rica (type locality).

This species is known only from its type locality in Costa Rica.

Check distribution from AntMaps.

Distribution based on specimens

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

Biology

Little is known about Acropyga keira. 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.

  • keira. Acropyga keira LaPolla, 2004a: 53, figs. 21, 39, 45 (w.m.) COSTA RICA.

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

Description

Worker

(n=4): TL: 2. 14-2.23; HW: 0.491-0.513; HL: 0.532-0.543; SL: 0.39-0.413; ML: 0.588-0.609; GL: 1.02-1.1; CI: 90.9-95.5; SI: 76.8-82.1.

Head: yellow; head longer than broad; covered in layer of short appressed hairs; posterior margin slightly concave; 9 segmented, incrassate antennae (note that males have 11 segments suggesting workers could have up to 10 segments); scape reaches or fails to reach posterior margin by about half length of pedicel; clypeus narrow, convex and covered in thick layer of suberect to erect hairs of varying lengths; mandible with 3 teeth; gap exists between anterior clypeal margin and inner mandibular margin. Mesosoma: yellow; pronotum in lateral view rises steeply toward mesonotum; covered in thin layer of short appressed hairs, except along posterior end where several erect hairs are present; mesonotum nearly at level of propodeum, covered in layer of short appressed hairs; metanotal area distinct; propodeum with layer of short appressed hairs; declivity steep. Gaster: petiole thick and erect; gaster yellow; covered in appressed hairs, with scattered erect hairs throughout, especially along posterior segmental margins.

Queen

Queens are not known for this species.

Male

(n=2): TL: 1.93-2.09; HW: 0.369-0.378; HL: 0.406-0.407; SL: 0.35-0.354; ML: 0.624-0.741; GL: 0.901-0.947; CI: 90.9-93.0; SI: 92.6-95.9

Head: brownish-yellow, darker toward apex around 3 prominent ocelli; head about as broad as long; posterior margin broadly rounded, with rounded posterolateral comers; eyes large, breaking outline of head in full frontal view; 11 segmented antennae; scape surpasses posterior margin by about half length of pedicel; clypeus slightly convex, covered in a dense layer of suberect to erect hairs; mandible typically with 2 teeth separated by a diastema; occasionally a small tooth develops near apical tooth, making mandible 3-toothed; a gap exists between anterior clypeal margin and inner mandibular margin. Mesosoma: yellow; pronotum collar-like, overarched by mesonotum, which is rounded anteriorly; mesonotum flat covered with layer of short appressed hairs; propodeum broadly rounded into an indistinct declivity. Gaster: petiole thick and erect; gaster yellow; covered in layer of short appressed hairs. Genitalia: parameres rectangular, coming to a point dorsocaudally; parameres mostly covered in layer of hairs of varying lengths, longest near middle of parameres, and then parameres bare toward base; cuspi cylindrical, bending toward apices with a number of short, peg-like teeth; digiti anvil-shaped, bent toward cuspi, meeting them dorsally, where there are a series of short peg-like teeth.

Type Material

Holotype worker, COSTA RICA: Heredia, La Selva Biological Station, elev. 50-150 m, 10026' N, 840 I' W (J. Longino) (INBC); 1 paratype worker, 1 paratype male, same locality as holotype (MCZC). The holotype is labeled JSL TYPE # 102.

Etymology

The specific epithet keira is Greek for cut short, in reference to the distinctly short hairs that are found on the head and mesosoma.

References