Acropyga kinomurai

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Acropyga kinomurai
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Acropyga
Species: A. kinomurai
Binomial name
Acropyga kinomurai
Terayama & Hashimoto, 1996
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.

LaPolla (2004) - A dealate queen was found in August. An A. kinomurai nest was taken under a stone. The mealybug Eumyrmococcus kinomurai has been found in the nests of A. kinomurai (Williams and Terayama, 2000).

Identification

LaPolla (2004) - Worker: 10-11 segmented antennae; flattish head distinctly square to rectangular in shape with prominent posterolateral corners and parallel sides; torulae widely separated; mandibles with 4 teeth, dorsum densely covered in hairs. Queen: as in worker with modifications expected for caste. Male: unknown. This species is unique in its appearance.

This is a bizarre looking and easy to recognize species with its uniquely square head and very widely set torulae. The placement of the torulae is particularily interesting because the great distance between the structures is unique among Acropyga. Based on the widely set torulae, A. kinomurai is provisionally placed in the myops species-group, pending discovery of worker-associated male specimens. This species also shares a very similar mesosomal structure (flat dorsum and short pronotum) with Acropyga lauta and Acropyga sauteri, other species in the myops species-group. The outer surface of the worker mandibles are similar to A. lauta in being covered in a dense layer of hairs suggesting a possible relationship between the two species. Unfortunately, A. lauta also is without known male specimens, and it has torulae that are close together, possibly indicating it is not a close relative of A. kinomurai.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Philippines.
Palaearctic Region: Japan (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Little is known about Acropyga kinomurai. 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

Males 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.

  • kinomurai. Acropyga (Rhizomyrma) kinomurai Terayama & Hashimoto, 1996: 7, figs. 16-18 (w.) JAPAN. LaPolla, 2004a: 65 (q.). See also: Terayama, Fellowes & Zhou, 2002: 25.

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

Description

Worker

LaPolla (2004) - (n=1): TL: 2.09; HW: 0.5; HL: 0.438; SL: 0.357; ML: 0.547; GL: 1.1; CI: 114.16; SI: 71.4. Head: yellow; covered in a thick layer of appressed to suberect hairs; head broader than long, distinctly square to rectangular in appearance; posterolateral corners distinct; posterior margin entire to slightly concave medially, with short erect hairs; 10-11 segmented, incrassate antennae; scape reaches to posterior margin; clypeus narrow and flat, with many long hairs (reaching toward apical teeth of closed mandibles) along anterior clypeal margin; torulae widely separated from each other; mandible with 4 teeth; dorsal surface of mandible with dense covering of hairs; gap exists between inner mandibular margin and anterior clypeal margin. Mesosoma: yellow; in lateral view pronotum rises steeply toward mesonotum; pronotum covered in dense layer of appressed to erect hairs; dorsum nearly flat, with propodeum slightly lower than mesonotum; mesonotum flat, covered in a dense layer of appressed to erect hairs; metanotal area indistinct; propodeum flat, covered in a dense layer of appressed to erect hairs; declivity gently sloping. Gaster: petiole thick and erect, with many short erect hairs on surface, reaching height of propodeum; gaster yellow; covered in layer of appressed hairs with scattered erect hairs throughout.

Queen

LaPolla (2004) - (n=1): TL: 3.0; HW: 0.603; HL: 0.525; SL: 0.514; ML: 0.924; GL: 1.55; CI: 114.86; SI: 85.24. As in worker with modifications expected for caste and the following differences: color darker than worker, being brownish-yellow; pronotum very narrow.

Type Material

LaPolla (2004) - Acropyga (Rhizomyrma) kinomurai Terayama & Hashimoto, 1996: 7. Holotype worker, JAPAN: Yoshino, Ishigaki-jima, Yaeyama Is., Okinawa Pref. (K. Kinomura) (Museum of Nature and Human Activities) [not examined). Specimens (worker and queen) examined for this study were from the type locality and had the same date and collector as listed in Terayama & Hashimoto (1996) for the holotype and subsequent paratypes, though the examined specimens were not labeled with any type designation.

References