Paltothyreus

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Paltothyreus
Paltothyreus tarsatus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Alliance: Odontomachus genus group
Genus: Paltothyreus
Mayr, 1862
Type species
Formica tarsata, now Paltothyreus tarsatus
Diversity
7 species
(Species Checklist)

Pachycondyla tarsata casent0003140 profile 1.jpg

Pachycondyla tarsata casent0003140 dorsal 1.jpg

Specimen labels

A small genus that is widespread in Sub-Saharan Africa. It is sister to Buniapone and is notable for its huge nests, noxious alarm pheromones, chemical recruitment, and prey transfer behavior. Paltothyreus tarsatus, the only valid species name for the genus, has a large number of junior synonyms and subspecies, suggesting the occurrence of significant morphological variation.

At a Glance • Termite specialist  
 

Identification

Schmidt and Shattuck (2014) - Diagnostic morphological apomorphies of Paltothyreus workers include their striate sculpturing, blunt clypeal projection, complex metapleural gland orifice (with both anterior and posterior cuticular flanges), and hypopygium armed with stout setae. This combination of characters does not occur in any other ponerine genus. Striate sculpturing and an armed hypopygium occur in several other ponerine genera, but never together, and never in combination with a blunt clypeal projection or complex metapleural gland orifice. The apomorphies of the clypeus and metapleural gland orifice are shared with Buniapone, but that genus lacks striate sculpturing and an armed hypopygium.

Keys including this Genus

Distribution

Paltothyreus is widespread and common in Sub-Saharan Africa, though it is patchily distributed (Arnold, 1915; Wheeler, 1922b). Wheeler (1922b) gives its range as encompassing all of Africa south of roughly 15° N latitude. Emery (1911) includes Madagascar in the range of the genus, but this has not been reported elsewhere and is presumably in error. (Schmidt and Shattuck 2014)

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

Paltothyreus Species Richness.png

Biology

Schmidt and Shattuck (2014) - Paltothyreus, the African stink ant, is so called because its workers produce powerfully smelly sulfur-containing alarm pheromones in their mandibular glands (Casnati et al., 1967; Crewe & Fletcher, 1974; Crewe & Ross, 1975a, 1975b). Paltothyreus occurs mainly in forests and forest-savannah transition zones. Colonies are relatively large, with as many as 2,500 workers (mean = 926 workers; Braun et al., 1994) but only a single queen. Nests are constructed in the ground or in abandoned termite nests (Kalule-Sabiti, 1980; Déjean et al., 1996, 1997) and are of exceptional size, encompassing surface areas of as much as 1,200 m2, with multiple entrance holes and extensive tunnel systems (Braun et al., 1994). Some colonies inhabit multiple distantly-separated nests connected by underground tunnels, which Braun et al. (1994) characterize as a form of polydomy. The tunnels and multiple nest entrances allow workers to access a large foraging area with minimal time spent in the open. During nest relocations, workers employ a pygidial gland-derived pheromone to recruit nestmates for tandem running (Hölldobler, 1984; Braun et al., 1994). Hölldobler (1980) discovered that Paltothyreus foragers visually navigate through their forest environments by memorizing the canopy overhead.

Paltothyreus are largely termite predators, though they do hunt or scavenge a broad range of other invertebrates, including other ants (Lévieux, 1977; Kalule-Sabiti, 1980; Déjean et al., 1993a, 1993b, 1999). Workers primarily forage singly, but will recruit nestmates to large prey or concentrated termite sources, using a trail pheromone produced by sternal glands (Hölldobler, 1984; Déjean et al., 1993a). Workers often sting their prey upon capture, and when collecting termites will stack multiple individuals between the mandibles for one return trip to the nest (Déjean et al., 1993b; López et al., 2000). Paltothyreus foragers often employ a unique form of group prey retrieval, termed prey chain transfer behavior (López et al., 2000), by which successful foragers (finders) returning to the nest will transfer their termite prey to other workers (receivers) at locations between the prey capture site and the nest. The finders then go back to capture more termites, while the receivers head to the nest, sometimes transferring the prey to yet other workers. López et al. (2000) hypothesize that this behavior increases the efficiency of prey capture and also serves as a simple form of recruitment.

The mating and dispersal behavior of Paltothyreus were studied by Villet et al. (1989). The abdominal glands of Paltothyreus males were studied by Hölldobler & Engel-Siegel (1982). Queens apparently chemically suppress the production of eggs by workers (Braun et al., 1994).

Castes

Queens and workers exhibit a pronounced dimorphism in size. Large numbers of winged gynes and males are produced annually in colonies, and this is a substantial energetic investment that allows independent colony foundation (Peeters et al. 2013).

Nomenclature

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

  • PALTOTHYREUS [Ponerinae: Ponerini]
    • Paltothyreus Mayr, 1862: 735. Type-species: Formica tarsata, by monotypy.
    • Paltothyreus junior synonym of Pachycondyla: Brown, in Bolton, 1994: 164.
    • Paltothyreus revived from synonymy: Schmidt & Shattuck, 2014: 124.

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

Description

Schmidt and Shattuck (2014):

Worker

Very large (TL 17-20 mm; Arnold, 1915) ants with the standard characters of Ponerini. Mandibles triangular and long, with a distinct basal groove. Clypeus with a blunt squarish anteromedial projection. Frontal lobes widely separated anteriorly by an extension of the clypeus. Eyes large, located anterior to head midline. Ocelli sometimes present in workers. Metanotal groove at most present as a faint suture. Propodeum broad dorsally. Propodeal spiracle ovoid. Metapleural gland orifice complex, with a broad cuticular flange posteriorly and a small cuticular flange anteriorly, together forming a deep transverse groove. Metatibial spur formula (1s, 1p). Tarsal claws with a single preapical tooth. Petiole surmounted by a thick scale. Subpetiolar process a deep keel. Sternite of A3 with a large keel-like anteroventral process. Tergite of A3 with blunt dorsolateral angles. Gaster with a moderate girdling constriction between pre- and post-tergites of A4. Hypopygium armed with a row of stout setae on either side of the sting. Head and body striate, with scattered to abundant pilosity and moderate pubescence. Color black.

Queen

Similar to worker but larger (TL 23 mm; Arnold, 1915) and winged.

Male

See descriptions in Emery (1911), Arnold (1915), and Wheeler (1922b).

References

  • Arnold, G. 1915. A monograph of the Formicidae of South Africa. Part I. Ponerinae, Dorylinae. Ann. S. Afr. Mus. 14: 1-159 (page 43, Paltothyreus in Ponerinae, Ponerini)
  • 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 382, Paltothyreus in Pachycondylinae, Ectatommini)
  • Bolton, B. 1994. Identification guide to the ant genera of the world. Cambridge, Mass.: Harvard University Press, 222 pp. (page 164, Paltothyreus as junior synonym of Pachycondyla)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 166, Paltothyreus as junior synonym of Pachycondyla)
  • Braun, U., Peeters, C. & Hölldobler, B. 1994. The giant nests of the African Stink Ant, Paltothyreus tarsatus (Formicidae, Ponerinae). Biotropica 26: 308-311.
  • Dalla Torre, K. W. von. 1893. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus. Vol. 7. Formicidae (Heterogyna). Leipzig: W. Engelmann, 289 pp. (page 32, Paltothyreus in Ponerinae)
  • Emery, C. 1895l. Die Gattung Dorylus Fab. und die systematische Eintheilung der Formiciden. Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 8: 685-778 (page 767, Paltothyreus in Ponerinae, Ponerini)
  • Emery, C. 1911e. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125 (page 62, Paltothyreus in Ponerinae, Ponerini [subtribe Pachycondylini])
  • Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 237, Paltothyreus in Ponerinae, Ponerini)
  • Mayr, G. 1862. Myrmecologische Studien. Verh. K-K. Zool.-Bot. Ges. Wien 12: 649-776 (page 714, Paltothyreus as genus (diagnosis in key))
  • Mayr, G. 1865. Formicidae. In: Reise der Österreichischen Fregatte "Novara" um die Erde in den Jahren 1857, 1858, 1859. Zoologischer Theil. Bd. II. Abt. 1. Wien: K. Gerold's Sohn, 119 pp. (page 15, Paltothyreus in Ponerinae [Poneridae])
  • Peeters, C., Braun, U. & Hölldobler, B. 2013. Large colonies and striking sexual investment in the African stink ant, Paltothyreus tarsatus (subfamily Ponerinae). African Entomology 21(1): 9-14.
  • Schmidt, C.A. & Shattuck, S.O. 2014. The higher classification of the ant subfamily Ponerinae (Hymenoptera: Formicidae), with a review of ponerine ecology and behavior. Zootaxa. 3817, 1–242 (doi:10.11646/zootaxa.3817.1.1)
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 135, Paltothyreus in Ponerinae, Ponerini)
  • 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 647, Paltothyreus in Ponerinae, Ponerini)