Acropyga yaeyamensis

AntWiki - Where Ant Biologists Share Their Knowledge
Jump to: navigation, search
Acropyga yaeyamensis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. yaeyamensis
Binomial name
Acropyga yaeyamensis
Terayama & Hashimoto, 1996
Synonyms

Collected from leaf litter at fairly high elevations (up to 1380 m), but otherwise nothing is known of its natural history.

Identification

LaPolla (2004) - Worker: 10-11 segmented antennae; mandible with 4 teeth; HW: < 0.425 mm. Queen: unknown. Male: 12 segmented antennae; parameres short, and roughly rectangular, coming to a dorsocaudal point. Compare with Acropyga oceanica.

This species most closely resembles Acropyga oceanica in its small size and 4 toothed mandible. It can be easily separated from A. oceanica based on a higher antennal segment count (10-11 segments versus 7-8 segments), and by the fact that the torulae of A. oceanica are extremely closely set together, whereas A. yaeyamensis has torulae positions that are more typical for the genus.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: Nepal.
Palaearctic Region: China, Japan (type locality).

This species has a wide range from Okinawa Island west to Nepal.

Check distribution from AntMaps.

Loading map...

Check specimen data from AntWeb

Biology

Little is known about Acropyga yaeyamensis. 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 have yet to be collected.

Nomenclature

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

  • yaeyamensis. Acropyga (Rhizomyrma) yaeyamensis Terayama & Hashimoto, 1996: 5, figs. 13-15 (w.) JAPAN. Senior synonym of guangxiensis, yunnanensis: LaPolla, 2004a: 74. See also: Terayama, Fellowes & Zhou, 2002: 26.
  • guangxiensis. Acropyga (Rhizomyrma) guangxiensis Terayama, Fellowes & Zhou, 2002: 23, figs. 4-6 (w.) CHINA. Junior synonym of yaeyamensis: LaPolla, 2004a: 74.
  • yunnanensis. Acropyga (Rhizomyrma) yunnanensis Terayama, Fellowes & Zhou, 2002: 27, figs. 20-26 (w.m.) CHINA. Junior synonym of yaeyamensis: LaPolla, 2004a: 74.

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

LaPolla (2004) - The synonyms, A. guangxiensis and A. yunnanensis, based on worker morphology are indistinguishable from each other and A. yaeyamensis. Terayama et al. (2002) discussed differences in mesosomal characters and number of ommattidia to separate the supposed species, but those characters are unreliable. The differences in mesosomal structure, the metanotal area being either distinct or indistinct, could easily be intraspecific variation, as is seen in many other Acropyga species. Terayama et al. (2002) state differences from 1 ommattidium to 4 ommattidia to separate A. guangxiensis and A. yunnanensis repectively, but such small differences in ommatidia number to separate species is unreliable since the extent of variation in that character remains unknown. Nonetheless, it is important to note that the male described in this study as A. yaeyamensis is geographically distant (Nepal) from the type locality. As males of this species are collected from across its range they should be examined with associated worker specimens to make certain there is not in reality more than one species present in a group of morphologically very similar workers. Although I have not examined the male described for A. yunnanensis, the figure provided matches the specimen used in this study for A. yaeyamensis very closely. Until males can be associated with workers and used to distinguish separate species I feel it unwarranted at this time to recognize more than one species.

Description

Worker

LaPolla (2004) - (n=3): TL: 1.28-1.38; HW: 0.378-0.419; HL: 0.43-0.454; SL: 0.244- 0.294; ML: 0.344-0.41; GL: 0.498-0.535; CI: 87.91-92.76; SI: 64.55-71.71.

Head: yellow; head longer than broad; posterior margin entire to slightly concave medially; covered in a thick layer of appressed hairs; 10-11 segmented, incrassate antennae; scape fails to reach posterior margin by about length of pedicel; clypeus narrow, with scattered erect hairs; mandible with 4 approximately similarly sized teeth; 4th tooth sometimes separated from others by a short diastema; slight gap between inner mandibular margin and anterior clypeal margin. Mesosoma: yellow; in lateral view, pronotum with short anterior shelf before rising toward mesonotum; with sparse covering of appressed to erect hairs; mesonotum rounded dorsally, with dense layer of appressed hairs to scattered erect hairs; mesonotum often higher than propodeum; metanotal area often distinct; propodeum rounded dorsally, with layer of appressed hairs; declivity steep. Gaster: petiole thick and erect reaching height propodeal spiracle; gaster yellow, covered in thick layer of appressed hairs, with scattered erect hairs throughout.

Male

LaPolla (2004) - Head: brownish-yellow, darker toward apex around 3 prominent ocelli; head longer than broad; covered in a thick layer of appressed hairs; 12 segmented, incrassate antennae; scape fails to reach posterior margin by about half length of the pedicel; clypeus narrow, slightly convex medially, with scattered erect hairs; mandible with 2 teeth, widely separated by a diastema; a slight gap between inner mandibular margin and anterior clypeal margin. Mesosoma: unfortunately the mesosoma of the single known male specimen was too badly distorted to be described properly. Gaster: brownish-yellow; covered in a thick layer of appressed hairs with scattered erect hairs throughout. Genitalia: in lateral view parameres short, roughly rectangular, dorsocaudally coming to a point; cuspi bent toward digiti, with short, peg-like teeth at apices; digiti about about as long as cuspi, apically anvil-shaped; digiti with short, peg-like teeth where they meet cuspi.

Type Material

LaPolla (2004):

Acropyga (Rhizomyrma) yaeyamensis Terayama and Hashimoto, 1996: 5 (w.). Holotype worker, JAPAN: Urauchi, Iriomote-jima, Yaeyama Is., Okinawa Pref. (M. Terayama) (Museum of Nature and Human Activities) [examined]. Terayama et al., 2002: 26, description and key.

Acropyga (Rhizomyrma) guangxiensis Terayama, Fellowes, and Zhou, 2002: 23 (w.). Holotype worker, CHINA: Guanxi, Huaping (J.R. Fellowes) (ICKH) [not examined]. NEW SYNONYM.

Acropyga (Rhizomyrma) yunnanensis Terayama, Fellowes, and Zhou, 2002: 27 (m.). Holotype male, CHINA: Yunnan, Xishuangbanna, Nangong-shan (Z. Xu) (ISYC) [not examined]. NEW SYNONYM.

References

  • Biinzli, G.H. 1935. Untersuchungen iiber coccidophile Ameisen aus den Kaffeefelden von Surinam. Mitteilungen der Schweizerischen Entomologischen Gesellschaft 16:455-593.*LaPolla, J. S. 2004. Acropyga (Hymenoptera: Formicidae) of the World. The American Entomological Institute 33(3): 1-130 (page 74, fig. 30C, worker, male described; senior synonym of guangxiensis, yunnanensis)
  • 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.
  • Terayama, M.; Fellowes, J. R.; Zhou, S. 2002. The East Asian species of the ant genus Acropyga Roger, 1862 (Hymenoptera: Formicidae: Formicinae). Edaphologia 70: 21-32 (page 26, description and key)
  • Terayama, M.; Hashimoto, Y. 1996. Taxonomic studies on the Japanese Formicidae, part 1. Introduction to this series and descriptions of four new species of the genera Hypoponera, Formica and Acropyga. Nat. Hum. Act. 1: 1-8 (page 5, figs. 13-15 worker described)
  • 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.