Acropyga hystrix

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

Acropyga hystrix casent0903179 p 1 high.jpg

Acropyga hystrix casent0903179 d 1 high.jpg

Specimen Labels

A nest was found in the soil under a log, but otherwise nothing is known of this species' natural history.

Identification

LaPolla (2004) - Worker: 11 segmented antennae; mandible with 6-7 teeth; pronotal and mesonotal dorsa with long erect hairs and a thinner layer of short erect hairs. Queen: As in worker with modifications expected for caste. Male: 12 segmented antennae; parameres broad, tapered to a sharp medial point, with many scattered erect hairs; mandible with 6 teeth. Compare with Acropyga acutiventris and Acropyga gelasis.

This species can be distinguished from Acropyga acutiventris by the lack of ridges on the surface of the mandible, and from Acropyga gelasis by not possessing a prominent "beak-like" median portion of the clypeus. Additionally, the erect mesosomal hairs of A. hystrix are longer than those of A. gelasis. Overall, this species, along with A. gelasis, is darker and with less pilosity than most other Acropyga species.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Borneo (type locality), Indonesia, Malaysia.

This species is known only from Sarawak on Borneo. Check distribution from AntMaps.

Distribution based on specimens

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

Biology

Little is known about Acropyga hystrix. 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.

  • hystrix. Acropyga hystrix LaPolla, 2004a: 63, figs. 25, 41, 46 (w.q.) BORNEO.

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

LaPolla (2004) - The species' placement within the myops species-group is based on the fact that A. hystrix workers possess widely separated torulae, and by the fact that the reproductives are very dark (dark brown to black), as are the reproductives of Acropyga myops. The mandibles of this species are similar to A. myops.

Description

Worker

(n=6): 2.24-2.69; HW: 0.543-0.647; HL: 0.607-0.665; SL: 0.511-0.549; ML: 0.596-0.7; GL: 0.964-1.33; CI: 89.46-96.68; SI: 82.53-90.98.

Head: brownish-yellow; darker brownish-yellow toward apex; head slightly longer than broad; posterior margin entire, with distinct long erect hairs scattered throughout; 11 segmented, incrassate antennae; scape reach or surpasses posterior margin by approximately length of pedicel; scape with erect hairs scattered throughout length; clypeus broad and wide, convex medially, with scattered erect hairs throughout; mandible broad, with 6-7 teeth; 3rd tooth from apical usually smaller than others; if with 7 teeth, 7th tooth at meeting of inner mandibular margin and masticatory margin, often smaller than other teeth. Mesosoma: brownish-yellow; in lateral view, pronotum rises steeply toward mesonotum; mesonotum with sparse covering of appressed hairs, long erect hairs posteriorly; mesonotum rounded, slightly higher than level of propodeum, with distinct long, erect hairs on dorsum; metanotal area distinct; propodeal dorsum flat, with sparse short appressed to erect hairs; declivity steep. Gaster: petiole thick and erect, reaching height of propodeal spiracle; gaster brownish-yellow; gaster dorsum slightly darker than venter; covered in layer of short, appressed hairs, though shinier than most other species; scattered erect hairs throughout.

Queen

(n=2): TL: 3.99-4.00; HW: 0.803-0.813; HL: 0.782-0.799; SL: 0.743; ML: 1.22-1.27; GL: 1.95-1.97; CI: 101.75-102.69; SI: 91.39-92.53. As in worker with modifications expected for caste and the following differences: color much darker than observed in worker, becoming almost black.

Male

(n=1): TL: 2.68; HW: 0.504; HL: 0.514; SL: 0.415; ML: 0.978; GL: 1.19; CI: 98.05; SI: 82.34.

Head: brownish-yellow; darker toward apex around 3 prominent ocelli; covered in layer of appressed hairs; longer, erect hairs along posterior margin; head about as broad as long; posterolateral comers rounded, giving head an overall round appearance; 12 segmented, slightly incrassate antennae; scapes surpass posterior margin by about length of first 3 funicular segments; clypeus broad, convex medially; mandible broad with 6 teeth; inner mandibular margin parallel with anterior clypeal margin. Mesosoma: brownish-yellow; pronotum small and collar-like, overarched by mesonotum; mesosomal dorsum with appressed hairs and scattered erect hairs; propodeum wide, sloping with an indistinct declivity. Gaster: petiole thick and erect; gaster brownish-yellow, covered in layer of appressed hairs with scattered erect hairs throughout. Genitalia: in lateral view, parameres broad, tapered to short medial points at midheight, with many scattered erect hairs; cuspi taper toward apices with peg-like teeth; cuspi slightly bent toward digiti; digiti erect, thick and apically truncated, with short, peg-like teeth on apices where they meet with cuspi.

Type Material

Holotype worker, MALAYSIA: Sarawak, 4th Div., G. Mulu National Park, RGS Expedition, Long Pala, lowland rainforest under a log (B. Bolton) (The Natural History Museum); 14 paratype workers, paratype queens, paratype males (BMNH) (Museum of Comparative Zoology). The holotype is labeled JSL TYPE # 110.

Etymology

The specific epithet hystrix is Greek for porcupine in reference to the long, stout erect hairs on the mesosoma.

References