Acropyga rubescens

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Acropyga rubescens
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. rubescens
Binomial name
Acropyga rubescens
Forel, 1894

Acropyga rubescens casent0903175 p 1 high.jpg

Acropyga rubescens casent0903175 d 1 high.jpg

Specimen Labels

Synonyms

Nothing is known about the biology of this ant.

Identification

LaPolla (2004) - Worker: 11 segmented antennae; mandible with 5 teeth and indistinct ridges that run along dorsal surface fading toward median portion of mandibles; scapes > 0.9 mm; many erect hairs on head, mesosoma and gaster giving ant a "spiky appearance." Queen: As in worker with modifications expected for caste. Male: As in Acropyga acutiventris, except hairier and penis valve differences. Compare with Acropyga acutiventris.

This species is the largest known Acropyga species, and is closely related to Acropyga acutiventris.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: India (type locality), Sri Lanka.

Check distribution from AntMaps.

Distribution based on specimens

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

Biology

Little is known about Acropyga rubescens. 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.

  • rubescens. Acropyga acutiventris var. rubescens Forel, 1894c: 418 (w.q.m.) INDIA. Senior synonym of rubens: Emery, 1925b: 28. Raised to species and senior synonym of bugnioni: LaPolla, 2004a: 33.
  • bugnioni. Acropyga acutiventris subsp. bugnioni Forel, 1911i: 226 (w.q.) SRI LANKA. Junior synonym of rubescens: LaPolla, 2004a: 33.
  • rubens. Acropyga acutiventris subsp. rubens Forel, 1911e: 286 (w) no locality stated. [This name most probably in error for rubescens.] Junior synonym of rubescens: Emery, 1925b: 28.

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

LaPolla (2004) - Acropyga rubescens has been elevated to species status based on 6 points of distinction from A. acutiventris: 1) setation of A. rubsecens is distinct: a) much denser hairs in general found across body; b) hairs on posterior margin of head often very long, much longer than seen in A. acutiventris; c) mesosomal hairs longer and denser; 2) A. rubescens larger overall; 3) with longer scapes (higher SI); 4) dorsal mandibular striate sculpture thinner disappearing about mid-way toward mandible articulation point with head; 5) shapes of penis valves differ; 6) both "forms" are sympatric in India/Sri Lanka region.

Description

Worker

LaPolla (2004) - (n=7): TL: 3.39-5.11; HW: 0.891-1.16; HL: 0.915-1.06; SL: 0.914-1.16; ML: 1.07-1.31; GL: 1.35-2.74; CI: 91.53-109.43; SI: 97.39-106.67.

Head: brownish-yellow to reddish-yellow; head about as broad as long; posterior margin concave; covered in a thick layer of appressed hairs, with many scattered, long erect hairs especially along posterior margin; eyes relatively large, placed at lower 114 of head; 11 segmented, incrassate antennae; scape nearly reaches or surpasses posterior margin up to length of pedicel; clypeus broad, slightly convex medially with many erect hairs, the longest ones along anterior clypeal margin; mandible with 5 uneven teeth; 3rd and 5th tooth (from apical to basal) smaller than others; dorsal surface of mandible covered in many erect hairs and with indistinct ridges originating near base of teeth and fading entirely toward middle of mandible; slight gap present between inner mandibular surface and anterior clypeal margin. Mesosoma: brownish-yellow to reddish-yellow; mesosoma covered throughout in dense layer of appressed hairs with scattered erect hairs of varying lengths; pronotum in lateral view typically with short shelf before rising sharply toward mesonotum; mesonotum rounded with many long erect hairs (many times longer than shortest erect hairs); metanotal area distinct; propodeum rounded, below level of mesonotum, propodeal dorsum flat before steep declivity; propodeum with dense layer of erect and appressed hairs. Gaster: brownish-yellow to reddish-yellow, darker than head and mesosoma; petiole thick and erect reaching height of propodeum; yellow to light brownish-yellow; gaster covered in thick layer of appressed hairs with many scattered erect hairs throughout giving a "spiky" appearance.

Queen

LaPolla (2004) - (n= l): TL: 6.16; HW: 1.36; HL: 1.36; SL: 1.34; ML: 2.23; GL: 2.57; CI: 100; SI: 98.53. As in worker with modifications expected for caste.

Male

LaPolla (2004) - (n= l ): TL: 3.52; HW: 0.644; HL: 0.665; SL: 0.611 ; ML: 1.25; GL: 1.6; CI: 96.84; SI: 94.88.

Head: brownish-yellow to reddish-yellow, darker around three prominent ocelli; head about as broad as long; covered in layer of appressed hairs with suberect to erect hairs; eyes large, breaking outline of head in full frontal view; 12 segmented, slightly incrassate antennae; scape surpasses posterior margin by about length of first two funicular segments; clypeus broad, relatively flat, with scattered short erect hairs; mandible with 4 teeth; a gap exists between inner mandibular margin and anterior clypeal margin. Mesosoma: light brownish-yellow to reddish-yellow; pronotum short and collar-like; mesonotum large, rounded anteriorly; mesonotum dorsum flat, with layer of shorter appressed hairs and scattered longer erect hairs throughout; propodeum lower than mesonotum and scutellum; declivity not distinct from propodeum. Gaster: petiole thick and erect; gaster brownish-yellow to reddish-yellow, darker dorsally; covered in dense layer of appressed hairs with scattered erect hairs throughout. Genitalia: in lateral view parameres thick, tapering to a rounded apex; parameres with medial dorsolateral extensions; cuspi short, bent toward approximately middle of digiti, where they meet with short, peg-like teeth at apex; digiti long and erect with short peg-like teeth where cuspi meet, apex rounded.

Type Material

LaPolla (2004):

Acropyga acutiventris rubescens Forel, 1894: 418, (w.q.m.). 10 syntype workers, 2 syntype queens, 3 syntype males, INDIA: Kanara (Bell) (American Museum of Natural History) (The Natural History Museum) (Museum of Comparative Zoology) [examined]. The designated lectotype is a worker labeled JSL TYPE # 111 and is deposited at MCZC.

Acropyga acutiventris bugnioni Forel, 1911c: 226 (w.q.). 2 syntype workers, SRI LANKA: no specific locality given (Naturhistorisches Museum Basel) [examined]. NEW SYNONYM.

Acropyga acutiventris rubens Forel, 19l1a: 286 (w.). Holotype worker, no locality provided (depository unknown) [not examined]. Synonym of A. rubescens by Emery, 1925 [probably a miss-spelling of rubescens (Bolton, 1995)] (here confirmed).

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.
  • Emery, C. 1925d. Hymenoptera. Fam. Formicidae. Subfam. Formicinae. Genera Insectorum 183: 1-302 (page 28, senior synonym of rubens)
  • Forel, A. 1894c. Les Formicides de l'Empire des Indes et de Ceylan. Part IV. J. Bombay Nat. Hist. Soc. 8: 396-420 (page 418, worker, queen, male described)
  • 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., 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.
  • LaPolla, J.S. 2004a. Acropyga of the world. Contributions of the American Entomological Institute. 33(3):1-130. PDF (page 3, raised to species: new status)
  • 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.