Acropyga romeo

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

Acropyga romeo usnment00441085 p 1 high.jpg

Acropyga romeo usnment00441085 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.

A. romeo was collected from leaf litter samples in Dicymbe dominated forest that also contained Acropyga stenotes, but otherwise nothing is known of its natural history. (LaPolla 2004)

Identification

LaPolla (2004) - Worker: 9 segmented antennae; mandible with 4 teeth; 4th tooth very small and offset from masticatory margin; head longer than broad, becoming narrower toward anterior end; small species (total length: < 1.5 mm). Queen: unknown. Male: unknown. Compare with Acropyga exsanguis, Acropyga keira and Acropyga smithii.

This species can be confused with Acropyga exsanguis and Acropyga keira. In all specimens of A. exsanguis examined in this study, the species always has had only 3 teeth on the mandible, with no sign of a smaller offset basal tooth as seen in A. romeo. A. keira also has only be observed to possess 3 teeth on its mandibles, and it has very short appressed hairs on its mesosoma, as opposed to the longer hairs observed in A. romeo. Finally both A. exsanguis and A. keira are larger species.

This species appears to belong to the decedens species-group, though until males are associated with workers its phylogenetic placement in the genus remains problematic. The combination of a narrow, 4-toothed mandible and a narrow, hairy clypeus suggests placement in the species group. This is among the smallest of the New World Acropyga species, around the same size as Acropyga smithii and Acropyga panamensis.

Key to New World Acropyga Workers

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Guyana (type locality).

Acropyga romeo species is known only from its type locality at the base of Mt. Ayanganna in western Guyana.

Check distribution from AntMaps.

Distribution based on specimens

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

Biology

Little is known about Acropyga romeo. 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.

  • romeo. Acropyga romeo LaPolla, 2004a: 57, figs. 22, 45 (w.) GUYANA.

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: 1.41-1.44; HW: 0.334-0.351; HL: 0.384-0.402; SL: 0.242-0.266; ML: 0.371-0.402; GL: 0.621-0.67; CI: 85.32-90.23; SI: 70.20-79.64.

Head: yellow; covered in a layer of short appressed hairs; head longer than broad, becoming narrower toward anterior end; posterior margin entire; 8-9 segmented, incrassate antennae; scape fails to reach posterior margin by about length of first 2 funicular segments; clypeus narrow, medially convex, covered in a dense layer of hairs; mandible narrow, with 4 teeth; apical tooth often much longer than other teeth; basal tooth very small, offset from masticatory margin; gap exists between anterior clypeal margin and inner mandibular margin. Mesosoma: yellow; in lateral view, pronotum rises steeply toward mesonotum; pronotum with a layer of appressed hairs and scattered erect hairs posteriorly; mesonotum at about same height as propodeum; mesonotum with layer of appressed to erect hairs; metanotal area distinct; propodeum short and flat, with appressed to erect hairs; declivity steep. Gaster: petiole thick and erect, slightly surpassing height of propodeal spiracle; gaster yellow; covered in dense layer of appressed hairs, with scattered erect hairs throughout.

Type Material

Holotype worker, GUYANA: Camp on Potaro River at base of Mt. Ayanganna, N 05" 18.08;W 0590 54.67, elev. 695 m +/-13 m (J.S. LaPolla et al.) (UGBC); 3 paratype workers, same locality as holotype (USNM) (MCZC). The holotype is labeled JSL TYPE # 106.

Etymology

Named in honor of Romeo Williams with admiration and thanks. Romeo is a Guyanese field guide and naturalist who made my 3 month expedition to Guyana in the autumn of 2002 in search of Acropyga and other ants possible. The name is treated as a noun in apposition.

References

  • Biinzli, G.H. 1935. Untersuchungen iiber coccidophile Ameisen aus den Kaffeefelden von Surinam. Mitteilungen der Schweizerischen Entomologischen Gesellschaft 16:455-593.
  • Brown, W.L., Jr. 1945. An unusual behavior pattern observed in a Szechuanese ant. Journal of the West China Border Research Society 15:185-186.
  • Buschinger, J., J. Heinze & K. Jessen. 1987. First European record ofa queen ant carrying a mealybug during her mating flight. NatUlwissenschaften 74:139-140.
  • Eberhard, W.G. 1978. Mating swarms ofa South American Acropygia [sic.] (Hymenoptera: Formicidae). Entomological News 89(1 & 2):14-16.
  • Eisner, T. 1957. A comparative morphological study ofthc proventriculus of ants (Hymenoptera: Formicidae). Bulletin ofthe Museum of Comparative Zoology 116:439-490.
  • Holldobler B . & E.O. Wilson. 1990. The Ants. Belknap Press, Cambridge, Massachusetts, 732 pp.
  • Johnson, c., D. Agosti, J.H. Delabie, K. Dumpert, OJ. Williams, M. von Tschimhaus & U. Maschwitz. 2001 . Acropyga and Azteca Ants with Scale Insects: 20 Million Years ofIntimate Symbiosis. American Museum Noviates 3335:1-18.
  • LaPolla, J.S. 2004a. Acropyga of the world. Contributions of the American Entomological Institute. 33(3):1-130. PDF
  • LaPolla, J.S., S.P. Cover & U.G. Mueller. 2002. Natural history of the mealybug-tending ant Acropyga epedana, with descriptions of the male and queen castes. Transactions of the American Entomological Society 128(3):367-376.
  • Prins, AJ. 1982. Review of Anoplolepis with reference to male genitalia, and notes on Acropyga. Annals of the South African Museum 89:215-247.
  • Weber, N.A. 1944. The Neotropical coccid-tending ants of the genus Acropyga Roger. Annals of the Entomological Society of America 37:89-122.
  • Wheeler, G.C. & J.C. Wheeler. 1953. The ant larvae of the subfamily Formicinae. Annals of the Entomological Society of America 46:126-171.
  • Wheeler, W.M. 1935b. Ants of the genus Acropyga Roger, with description ofa new species. Journal of the New York Entomological Society 43:321-329.
  • Williams, D J . 1998. Mealybugs of the genera Eumyrmococcus Silvestri and Xenococcus Silvestri associated with the ant genus Acropyga Roger and a review of the subfamily (Hemiptera, Coccoidea, Pseudoccidae). Bulletin of the British Museum (Natural History)(Entomology) 67:1-64.