| Acropyga yushi|
Little is known about this Taiwanese Acropyga species.
Terayama (2009) - Resembling Acropyga yaeyamensis but easily separated from the latter by the 11-segmented antenna, large eye consisting of about 10 facets, moderately convex promesonotal dorsum, and straight dorsal margin and concave posterior margin of propodeum.
Distribution based on Regional Taxon Lists
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Distribution based on specimens
Little is known about Acropyga yushi. 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.
Only known from workers, although Teramaya (2009) noted: A possible female of this species was collected in Nanshanxi, Nanfen-Cun, Nantou Pref. (collection date: 21. viii. 1987).
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- yushi. Acropyga yushi Terayama, 2009: 205, figs. 317, 318 (w.) TAIWAN.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
HL 0.70, HW 0.63, SL 0.58, WL 0.75, PL 0.05, PH 0.18, DPW 0.13, TL 2.0.
Holotype worker. Head 1.12 times as long as wide, with concave posterior margin and parallel sides; frons and vertex largely smooth, but very weakly microreticulate. Mandible with 4 acute triangular teeth. Antenna with 11 segments ; scape not reaching posterior margin of head, 3rd to 8th segments each wider than long, 9th and 10th segments each as long as wide; terminal segment 2.3 times as long as wide. Eye consist of about 10 facets; ca. 0.05 rum long. Promesonotum with weakly convex dorsal margin and about 10 erect hairs on the dorsum; metanotum incised dorsally; propodeum with straight dorsal margin and concave posterior margin. Petiole thin and high, dorsum forming acute angle; in frontal view, node with straight dorsal margin and parallel sides.
Color. Head, alitrunk, petiole yellow; gaster brownish.
The specific epithet is the Chinese noun Yushi which is the name of a Taiwanese god.