Rhopalothrix

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Rhopalothrix
Rhopalothrix ciliata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Rhopalothrix
Mayr, 1870
Type species
Rhopalothrix ciliata
Diversity
16 species
(Species Checklist)

Rhopalothrix ciliata casent0423544 profile 1.jpg

Rhopalothrix ciliata

Rhopalothrix ciliata casent0423544 dorsal 1.jpg

Specimen Label

Synonyms

The genus Rhopalothrix is a rare inhabitant of wet forest leaf litter and soil.

Identification

Rhopalothrix belong to the tribe Basicerotini. While most basicerotines have triangular mandibles, Rhopalothrix mandibles are arched shafts with an apical fork similar to many dacetines.

The Basicerotini tribe is taxonomically problematic as there is no single accepted classification of its species into genera. Baroni Urbani and de Andrade (2007) synonymized the tribe Basicerotini with Dacetini and proposed that all basicerotine genera be placed in the genus Basiceros. Longino and Boudinot (2013) revised a distinctive Rhopalothrix isthmica clade and recognized 13 species. The Rhopalothrix isthmica clade was defined by two synapomorphies: (1) absence of squamiform setae on the face, and (2) development of shallow arcuate grooves and ridges on the face. All the species share a similar habitus, being small, nearly eyeless, pale brown, with uniformly matte surface, and a characteristically broad, lumpy face. The R. isthmica clade is strictly Neotropical, with the greatest abundance and diversity in Central America. They also noted there were an additional 3 species, outside of this clade, in the genus: Rhopalothrix ciliata from Colombia, Rhopalothrix diadema from New Guinea, and Rhopalothrix orbis from Australia. These latter three species all have squamiform setae on the face and their heads are more elongate and less flattened, more like other basicerotines.

Keys including this Genus

Keys to Species in this Genus

Distribution

World distribution based on political regions. View/Edit Data
Rhopalothrix Distribution.png Worlddistribution legend.jpg

Species richness

Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data

Rhopalothrix Species Richness.png

Biology

Longino and Boudinot (2013) - Knowledge of the biology of the Rhopalothrix isthmica clade of Rhopalothrix is conjectural; a nest has never been recovered and a live specimen never seen. What we know is based on locations and frequencies of capture using various mass-sampling methods. Specimens are known from wet to moderately seasonal forest, from sea level to 2140 m elevation. At higher elevation, they are found in diverse mesophyll forest and in forests with various combinations of Liquidambar and montane oak. In Costa Rica, they are restricted to the wet forests of the Atlantic slope, to 1500 m on the Barva Transect in the Cordillera Volcánica Central and to 800 m in the Cordillera de Tilarán. The genus is unknown from the Monteverde cloud forest at 1500 m, the lowland wet forests of the Osa Peninsula, and the lowland tropical dry forests of Guanacaste, in spite of intensive collecting efforts in these areas. Further north in Central America they can occur at higher elevations.

In quantitative sampling at La Selva Biological Station, in the Atlantic lowlands of Costa Rica, occurrences were relatively more frequent in soil/litter cores than in samples of sifted litter from the soil surface. This suggests that nests are subterranean, with workers only occasionally venturing up into the litter layer. Dealate queens are known for a few species, occurring occasionally in Winkler or Berlese samples. Alate queens of one La Selva species were found in canopy fogging samples, one each in two separate fogging events. Oddly, alate queens have not been found in the many Malaise samples from La Selva. Males remain unknown.

Castes

Nomenclature

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

  • RHOPALOTHRIX [Myrmicinae: Basicerotini]
    • Rhopalothrix Mayr, 1870a: 415. Type-species: Rhopalothrix ciliata, by subsequent designation of Wheeler, W.M. 1911f: 172.
    • Rhopalothrix senior synonym of Acanthidris, Heptastruma: Brown & Kempf, 1960: 230.
    • Rhopalothrix junior synonym of Basiceros: Baroni Urbani & De Andrade, 2007: 88.
  • ACANTHIDRIS [junior synonym of Rhopalothrix]
    • Acanthidris Weber, 1941a: 188. Type-species: Acanthidris isthmicus, by original designation.
    • Acanthidris junior synonym of Rhopalothrix: Brown & Kempf, 1960: 230.
  • HEPTASTRUMA [junior synonym of Rhopalothrix]
    • Heptastruma Weber, 1934a: 54. Type-species: Heptastruma wheeleri (junior secondary homonym in Rhopalothrix, replaced by Rhopalothrix weberi), by original designation.
    • Heptastruma junior synonym of Rhopalothrix: Brown & Kempf, 1960: 230.

Longino and Boudinot (2013) provided the following regarding key characters for the genus:

Species of the R. isthmica clade vary in size, armature of the mandible, shape of the labrum, shape of the propodeal tooth and infradental lamella, and the distribution and abundance of squamiform setae on the gaster. Size is measured as head width (HW), the maximum width of the head capsule in full-face view. There was little variation in allometry among traditional metric characters (head length, scape length, mesosoma length, etc.), obviating the need for extensive measurements. The inner surface of the mandible curves through the masticatory margin and has a variable number of teeth or small denticles. The apical fork is perpendicular to the dorsal surface of the mandible and comprises two long spiniform teeth: the subapical and apical. The subapical tooth is visible as the apparent apex of the mandible in dorsal view; the shorter apical tooth is below it. There are usually two small intercalary denticles between the subapical and apical teeth. A small, usually reclinate denticle occurs on the inner base of the subapical tooth, with a diastema between it and the more basal teeth of the masticatory margin. This denticle varies in size and distinctness and may be extremely minute or absent. In one species it is pronounced and recurved, directed back toward the base of the mandible. The shape of the labrum is highly variable and of great diagnostic value. In some species the apical lobes of the labrum are secondarily divided, thence bilobed; we term these the lateral and medial lobules. When preparing specimens, it helps to open at least one mandible by inserting an insect pin between the mandibles and labrum and wedging open a mandible. This allows clear viewing of the mandibular dentition and the labrum.

The posterior face of the propodeum always has a pair of translucent longitudinal lamellae, of varying width, and with the dorsal portion forming an obtuse, right-angle, or acute tooth. The infradental lamella is the portion of the lamella ventral to the tooth. Varying numbers of squamiform (paddle-shaped) setae occur on the gaster (Fig. 3). Setae are always present on the second through fourth gastral tergites (abdominal segments 5–7, small sclerites at the apex of the gaster). The first gastral tergite, which covers most of the gaster, varies from being devoid of setae to having a dense, even coverage. The setae vary in the length of the stem and the degree of inclination. The meso- and metabasitarsus and the apices of the tibiae also have squamiform setae varying in number and size.

References

  • Ashmead, W. H. 1905c. A skeleton of a new arrangement of the families, subfamilies, tribes and genera of the ants, or the superfamily Formicoidea. Can. Entomol. 37: 381-384 (page 384, Rhopalothrix in Cryptoceridae, Dacetini)
  • Baroni Urbani, C.; De Andrade, M. L. 1994. First description of fossil Dacetini ants with a critical analysis of the current classification of the tribe (Amber Collection Stuttgart: Hymenoptera, Formicidae. VI: Dacetini). Stuttg. Beitr. Naturkd. Ser. B ( (page 32, Rhopalothrix in Myrmicinae, Dacetini)
  • Bolton, B. 1994. Identification guide to the ant genera of the world. Cambridge, Mass.: Harvard University Press, 222 pp. (page 105, Rhopalothrix in Myrmicinae, Basicerotini)
  • Bolton, B. 1998a. Monophyly of the dacetonine tribe-group and its component tribes (Hymenoptera: Formicidae). Bull. Nat. Hist. Mus. Entomol. Ser. 67: 65-78 (page 67, Rhopalothrix in Myrmicinae, Basicerotini)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 185, Rhopalothrix in Myrmicinae, Basicerotini)
  • Brown, W. L., Jr. 1948e. A preliminary generic revision of the higher Dacetini (Hymenoptera: Formicidae). Trans. Am. Entomol. Soc. 74: 101-129 (page 102, Rhopalothrix in Myrmicinae, Dacetini)
  • Brown, W. L., Jr. 1949h. Revision of the ant tribe Dacetini: IV. Some genera properly excluded from the Dacetini, with the establishment of the Basicerotini new tribe. Trans. Am. Entomol. Soc. 75: 83-96 (page 92, Rhopalothrix in Myrmicinae, Basicerotini)
  • Brown, W. L., Jr.; Kempf, W. W. 1960. A world revision of the ant tribe Basicerotini. Stud. Entomol. (n.s.) 3: 161-250 (page 230, Rhopalothrix senior synonym of Acanthidris and Heptastruma, and revision of genus; Rhopalothrix in Myrmicinae, Basicerotini)
  • Chapman, J. W.; Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327 (page 105, Rhopalothrix in Myrmicinae, Dacetini)
  • Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 145, Rhopalothrix in Myrmicinae)
  • Donisthorpe, H. 1943h. A list of the type-species of the genera and subgenera of the Formicidae. [concl.]. Ann. Mag. Nat. Hist. 11(10): 721-737 (page 724, Rhopalothrix in Myrmicinae, Dacetini)
  • Emery, C. 1877b. Saggio di un ordinamento naturale dei Mirmicidei, e considerazioni sulla filogenesi delle formiche. Bull. Soc. Entomol. Ital. 9: 67-83 (page 81, Rhopalothrix in Myrmicidae, Cryptoceridae)
  • Emery, C. 1895l. Die Gattung Dorylus Fab. und die systematische Eintheilung der Formiciden. Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 8: 685-778 (page 770, Rhopalothrix in Myrmicinae, Dacetini)
  • Emery, C. 1914e. Intorno alla classificazione dei Myrmicinae. Rend. Sess. R. Accad. Sci. Ist. Bologna Cl. Sci. Fis. (n.s.) 18: 29-42 (page 42, Rhopalothrix in Myrmicinae, Dacetini)
  • Emery, C. 1924f [1922]. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [concl.]. Genera Insectorum 174C: 207-397 (page 328, Rhopalothrix in Myrmicinae, Dacetini)
  • Forel, A. 1892d. Attini und Cryptocerini. Zwei neue Apterostigma-Arten. Mitt. Schweiz. Entomol. Ges. 8: 344-349 (page 344, Rhopalothrix in Myrmicinae, Dacetini)
  • Forel, A. 1893b. Sur la classification de la famille des Formicides, avec remarques synonymiques. Ann. Soc. Entomol. Belg. 37: 161-167 (page 164, Rhopalothrix in Myrmicinae, Dacetini)
  • Forel, A. 1895b. A fauna das formigas do Brazil. Bol. Mus. Para. Hist. Nat. Ethnogr. 1: 89-139 (page 133, Rhopalothrix in Myrmicinae, Dacetini)
  • Forel, A. 1899d. Formicidae. [part]. Biol. Cent.-Am. Hym. 3: 25-56 (page 41, Rhopalothrix in Myrmicinae, Dacetini)
  • Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 246, Rhopalothrix in Myrmicinae, Dacetini)
  • Mayr, G. 1870a. Formicidae novogranadenses. Sitzungsber. Kais. Akad. Wiss. Wien Math.-Naturwiss. Cl. Abt. I 61: 370-417 (page 415, Rhopalothrix as genus)
  • Taylor, R. W. 1990c. New Asian ants of the tribe Basicerotini, with an on-line computer interactive key to the twenty-six known Indo-Australian species (Hymenoptera: Formicidae: Myrmicinae). Invertebr. Taxon. 4: 397-425 (page 397, Rhopalothrix in Myrmicinae, Basicerotini)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 141, Rhopalothrix in Myrmicinae, Dacetini)
  • Wheeler, W. M. 1911g. A list of the type species of the genera and subgenera of Formicidae. Ann. N. Y. Acad. Sci. 21: 157-175 (page 172, Type-species: Rhopalothrix ciliata, by subsequent designation)
  • Wheeler, W. M. 1922i. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VII. Keys to the genera and subgenera of ants. Bull. Am. Mus. Nat. Hist. 45: 631-710 (page 666, Rhopalothrix in Myrmicinae, Dacetini)