Acanthognathus

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Acanthognathus
Temporal range: 19–0 Ma
Burdigalian, Early Miocene – Recent
Acanthognathus ocellatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Acanthognathus
Mayr, 1887
Type species
Acanthognathus ocellatus
Diversity
7 species
1 fossil species
(Species Checklist)

Acanthognathus-ocellatusL.jpg

Acanthognathus ocellatus

Acanthognathus-ocellatusD.jpg

Specimen Label

Species in this Central and South American genus are found in rotten logs, hollow twigs and branches and sections of wood buried in leaf litter. Colony size is rather small, often less than 20 workers. Individual foragers can be seen hunting collembola prey with mandibles wide open on the surface of leaf litter.

At a Glance • Trap-Jaw  
 

Identification

Mandibles linear and elongate, their bases extremely closely approximated and with kinetic mode of action, each with an apical fork of 3 spiniform teeth that interlock at full closure. Preapical dentition sometimes present but often absent. Mandibles at full gape open to 170 degrees or more. Basal process of mandible a long curved spur that is minutely bifurcated apically; when mandibles fully closed the basal processes cross over and are ventral to the labrum and at the apex of the labio-maxillary complex; when fully open the mandibles are braced in that position by opposition of the basal processes alone. Trigger hairs arise from the mandibles (one from each); trigger hairs lie flat against margin when mandible closed, becoming erect as mandibles open. Palp formula 0,1. Labrum extremely reduced to vestigial, represented by a narrow Y-shaped sclerite; labrum not taking part in mandibular locking mechanism. Buccal cavity narrow, parallel-sided anteriorly; labio-maxillary complex narrow.

Keys including this Genus

Keys to Species in this Genus

Distribution

The seven species in this genus are found in Central and South America. The single extinct species is Miocene age from Dominican Republic amber.

World distribution based on political regions. View/Edit Data
Acanthognathus 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

Acanthognathus Species Richness.png

Biology

Ants of the genus Acanthognathus stalk small insects and catch their prey by a strike with their long, thin mandibles. The mandibles close in less than 2.5 ms and this movement is controlled by a specialized closer muscle. In Acanthognathus, unlike other insects, the mandible closer muscle is subdivided into two distinct parts: as in a catapult, a large slow closer muscle contracts in advance and provides the power for the strike while the mandibles are locked open. When the prey touches specialized trigger hairs, a small fast closer muscle rapidly unlocks the mandibles and thus releases the strike. The fast movement is steadied by large specialized surfaces in the mandible joint and the sensory-motor reflex is controlled by neurons with particularly large, and thus fast-conducting, axons.

Morphology

Worker Morphology

 • Antennal segment count 11 • Antennal club 2 • Palp formula 0,1 • Total dental count 3-8 • Spur formula 0, 0 • Eyes present • Scrobes absent • Sting present

Nomenclature

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

  • ACANTHOGNATHUS [Myrmicinae: Dacetini]
    • Acanthognathus Mayr, 1887: 578. Type-species: Acanthognathus ocellatus, by monotypy.

Baroni Urbani & De Andrade (2007) - Synapomorphies resulting from our analysis:

Worker (and gyne) metapleural gland very close to propodeal spiracle. CI 0.62, RI 0.40. This trait appears also in Epopostruma, Microdaceton, Protalaridris, a. o. as coded also by BOLTON (1999, Table 1) for his Dacetonini.

Worker (and gyne) scape straight at base. CI 0.50, RI 0.33. The straight condition of Acanthognathus is shared with Daceton.

Worker (and gyne) antennae 11-jointed. CI 0.20, RI 0.50 for the 11-12 jointed state.

This list, however, does not evidentiate the main synapomorphy for the species of the genus, i.e. our char. #13, state 2, the basimandibular process long and apically bifurcated. The reason for this omission is a purely logical pitfall: since state #2 appears only in Acanthognathus and state #1 is present in all the other genera of the clade, it is impossible to ascertain whether the ancestor of the whole clade presented state #1 or #2 and hence if #2 is exclusive of Acanthognathus or common to Acanthognathus and the hypothetical ancestor of the whole clade.

See also

  • Dalla Torre, 1893: 148 (catalogue)
  • Emery, 1924d: 317 (diagnosis, catalogue)
  • Smith, M.R. 1944c: 150 (all species key)
  • Brown & Kempf, 1969: 89 (diagnosis, all species revision, key)
  • Kempf, 1972a: 9 (catalogue)
  • Bolton, 1994: 106 (synoptic classification)
  • Bolton, 1995a: 1047 (census)
  • Bolton, 1995b: 53 (catalogue)
  • Gronenberg, Brandão, et al. 1998: 227 (mandible mechanism)
  • Bolton, 1999: 1650 (diagnosis, review of genus, phylogeny)
  • Bolton, 2000: 15 (diagnosis, species synopsis)
  • Galvis & Fernández, 2009: 247 (all species key)

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, Acanthognathus in Cryptoceridae, Dacetini)
  • Baroni Urbani, C. 1994b. [Untitled. Strumigenys schleeorum Baroni Urbani n. sp.] Pp. 35-38 in: Baroni Urbani, C., De Andrade, M. L. 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. PDF
  • Baroni Urbani, C. and de Andrade, M.L. 2007. The ant tribe Dacetini: limits and constituent genera, with descriptions of new species. Annali del Museo Civico di Storia Naturale “G. Doria”. 99:1-191.
  • Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 53, catalogue of species)
  • Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). J. Nat. Hist. 3 33: 1639-1689 (page 1650, diagnosis, review of genus, phylogeny)
  • Bolton, B. 2000. The ant tribe Dacetini. Mem. Am. Entomol. Inst. 65: 1-1028 (page 15, diagnosis, species synopsis)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 186, Acanthognathus in Myrmicinae, Dacetini)
  • Brandão, C. R. F. 1991. Adendos ao catálogo abreviado das formigas da região Neotropical (Hymenoptera: Formicidae). Rev. Bras. Entomol. 35: 319-412 (page 391, distribution of species)
  • Brown, W. L., Jr. 1948e. A preliminary generic revision of the higher Dacetini (Hymenoptera: Formicidae). Trans. Am. Entomol. Soc. 74: 101-129 (page 102, Acanthognathus in Myrmicinae, Dacetini)
  • Brown, W. L., Jr.; Kempf, W. W. 1969. A revision of the neotropical dacetine ant genus Acanthognathus (Hymenoptera: Formicidae). Psyche (Camb.) 76: 87-109 PDF (page 87, Revision of genus, key to species)
  • Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 148, Acanthognathus in Myrmicinae)
  • Dietz, B. H.; Brandão, C. R. F. 1993. Comportamento de caça e dieta de Acanthognathus rudis Brown & Kempf, com comentários sobre a evolução da predação em Dacetini (Hymenoptera, Formicidae, Myrmicinae). Rev. Bras. Entomol. 37: 683-692 (page 683, see also)
  • Dietz, B. H., Brandao, C. R. F. 1993. Hunting behavior and diet of Acanthognathus rudis Brown and Kempf, with comments on the evolution of predation by Dacetini ants (Hymenoptera, Formicidae, Myrmicinae). Revista Brasileira de Entomologia 37:683-692.
  • 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, Acanthognathus in Myrmicinae, Dacetini)
  • Emery, C. 1924f [1922]. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [concl.]. Genera Insectorum 174C: 207-397 (page 317, Acanthognathus in Myrmicinae, Dacetini)
  • Forel, A. 1892d. Attini und Cryptocerini. Zwei neue Apterostigma-Arten. Mitt. Schweiz. Entomol. Ges. 8: 344-349 (page 344, Acanthognathus 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, Acanthognathus in Myrmicinae, Dacetini)
  • Forel, A. 1895b. A fauna das formigas do Brazil. Bol. Mus. Para. Hist. Nat. Ethnogr. 1: 89-139 (page 136, Acanthognathus 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, Acanthognathus in Myrmicinae, Dacetini)
  • Galvis, J. P. & Fernández, F. 2009. Ants of Colombia X. Acanthognathus with the description of a new species (Hymenoptera: Formicidae) Revista Colombiana de Entomología 35 (2): 245-249 PDF
  • Gronenberg, W.; Brandão, C. R. F.; Dietz, B. H.; Just, S. 1998. Trap-jaws revisited: the mandibular mechanism of the ant Acanthognathus. Physiol. Entomol. 23: 227-240 (page 227, mandible mechanism)
  • Kempf, W. W. 1972b. Catálogo abreviado das formigas da regia~o Neotropical. Stud. Entomol. 15: 3-344 (page 9, distribution of species)
  • Kempf, W. W. 1975 ("1974"). Report on Neotropical Dacetine ant studies. Revista Brasileira de Biologia 34:411-424.
  • Mayr, G. 1887. Südamerikanische Formiciden. Verhandlungen der k.k. Zoologisch-Botanischen Gesellschaft in Wien 37: 511-632. [(30).ix.1887.] PDF (page 567, 578, diagnosis in key; Acanthognathus as genus)
  • Serna, F. 1999. Hormigas de la zona de influencia del Proyecto Hidroeléctrico Porec II. Unpublished Master’s Thesis, Universidad Nacional de Colombia, xiv + 250 pp.
  • Smith, M. R. 1944c. A key to the genus Acanthognathus Mayr, with the description of a new species (Hymenoptera: Formicidae). Proc. Entomol. Soc. Wash. 46: 150-152 (page 150, key to species)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 141, Acanthognathus in Myrmicinae, Dacetini)
  • 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, Acanthognathus in Myrmicinae, Dacetini)
  • Wheeler, G. C.; Wheeler, J. 1969. The larva of Acanthognathus (Hymenoptera: Formicidae). Psyche (Camb.) 76: 110-113 PDF