Rogeria exsulans

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Rogeria exsulans
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Solenopsidini
Genus: Rogeria
Species: R. exsulans
Binomial name
Rogeria exsulans
Wilson & Taylor, 1967

Rogeria exsulans has been collected only at 600-700m on a single island in the middle of the South Pacific. Most collections specify a rain forest habitat, where it has been found under dead bark, in rotten logs, in moss and ferns on trees and in berlesate of moss on logs and tree trunks.

Identification

Kugler (1994) - creightoni species group. WL 0.68-0.84mm. Eye fairly large, oval. Propodeal spiracle faces posterolaterally. Petiole with lamellate keel and dentate inferior process. Terminal segments of gaster rotated ventrad. Sides of head areolate-rugose; posterior head and promesonotum strongly areolate. Scapes with decumbent and a few short, suberect hairs. No erect hair on extensor surfaces of legs. Mostly abundant decumbent to subdecumbent hair on dorsa of head, mesosoma, nodes and gaster T1 (sparse erect hair on head and mesosoma); not sorting into two distinct kinds of pilosity.

The only other Pacific species, Rogeria stigmatica and Rogeria megastigmatica are easily distinguished from Rogeria exsulans by their lack of a petiolar keel and inferior process, as well as other features listed above.

The species most similar to exsulans is Central American. Rogeria belti has some members with similar size, habitus, eye size, clypeus shape, a distinct petiolar keel, strong areolate sculpture, and intergrading types of hairs on mesosoma. However, belti workers still differ in having generally longer propodeal spines (PSI 0.19-0.24), less prominent petiolar keel, and distinct long/erect and short/decumbent pilosities on the gaster.

Keys including this Species

Distribution

Only known from the island of Upolu, (Samoa).

Distribution based on Regional Taxon Lists

Indo-Australian Region: Samoa (type locality).

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

The following is modified from Kugler (1994): Little is known about these cryptic ants. Collection records typically range from sea level to 1000m, but five species extend higher and two (Rogeria unguispina and Rogeria merenbergiana) can be found at 2000m. Rogeria are generally collected in moist forests (primary or secondary forests, coffee or cacao plantations), but at higher elevations can be found in pastures (Rogeria leptonana, Rogeria merenbergiana). Several species (Rogeria creightoni, Rogeria cuneola, Rogeria foreli) have been found in moist and dry climates. Rogeria foreli is the most unusual, with some members dwelling at over 1800m in the temperate mountains of southern Arizona.

Most species have only been collected as strays or by Berlese or Winkler sampling, from leaf litter and rotten wood, but occasionally among epiphytes and moss (Rogeria belti, creightoni, Rogeria exsulans). Nests of several species (belti, Rogeria blanda, merenbergiana) have been found under the loose bark of rotten logs. Nests of blanda and Rogeria tonduzi have been taken from the trunks of cacao trees. A nest of Rogeria leptonana was found at 1750m under a rock in a pasture.

Nests are rarely found. Males are known for only four species (belti, blanda, leptonana and Rogeria stigmatica) and queens associated through nest series for only nine species.

Castes

Known only from workers.

Nomenclature

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

  • exsulans. Rogeria exsulans Wilson & Taylor, 1967: 74, fig. 60 (w.) SAMOA. See also: Kugler, C. 1994: 64.

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

Description

Worker

Kugler (1994) - TL 2.5-3.0, HL 0.62-0.71, HW 0.52-0.64, EL 0.08-0.11 (20-26 facets), PW 0.37-0.45, WL 0.68-0.84, SpL 0.10-0.15, PetL 0.26-0.33, PpetL 0.15-0.17mm, CI 0.84-0.90, OI 0.19-0.21, SI 0.81-0.85, PSI 0.14-0.19. N=4

Kugler 1994 fig 44-48

Some mandibles with 6 teeth (5 decreasing in size then a large basal), but usually the small penultimate basal tooth is replaced by 2 denticles, or by a gap and 1 denticle. Pal pal formula 3,2. Clypeal apron medially emarginate. Back of head in dorsal view convex or flat medially; temples broadly rounded. Promesonotal profile may be evenly rounded, but more often angular. Metanotal groove usually distinct, producing a step between promesonotum and propodeum, but weak in two specimens. Propodeal spiracles more than one diameter from nearest edge of infradental lamella. Node short, evenly convex. Postpetiolar sternum relatively long, flat; postpetiole from above subtrapezoidal, as in Fig. 51. Sting apparatus as in creightoni-group diagnosis.

Longitudinal rugae of frontal lobes and median head gradually change to strongly areolate on posterior head. Cheeks and laterodorsa longitudinally areolate-rugose. Intervals on head dorsum vaguely undulate, but shiny; intervals on sides and posterior head smooth and shiny. Promesonotum for the most part strongly areolate, but several elongate cells may occupy the midline of the pronotal disc, and often the pronotal sides have weaker areolate sculpture. Meso- and metapleura confused areolate-rugose. Mesosoma microsculpture reduced; intervals in macrosculpture uneven, but very shiny. Petiolar node with weak to vestigial areolate macrosculpture and vague microareolate background. Postpetiolar node shiny, nearly smooth throughout.

Head, mesosoma dark reddish-brown, waist and anterior and posterior ends of gaster somewhat lighter. Mandibles, clypeus, antennae, and legs yellowish-brown.

Type Material

Kugler (1994) - Holotype SAMOA: Upolu (T. E. Woodward) (Holotype Museum of Comparative Zoology; paratypes Australian National Insect Collection, MCZ) [Holotype and 30 paratypes examined].

References

  • Kugler, C. 1994. A revision of the ant genus Rogeria with description of the sting apparatus (Hymenoptera: Formicidae). J. Hym. Res. 3: 17-89 (page 64, see also)
  • Wilson, E. O.; Taylor, R. W. 1967b. The ants of Polynesia (Hymenoptera: Formicidae). Pac. Insects Monogr. 14: 1-109 (page 74, worker described)