Gesomyrmex

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Gesomyrmex
Gesomyrmex chaperi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Gesomyrmecini
Genus: Gesomyrmex
Mayr, 1868
Type species
Gesomyrmex hoernesi
Diversity
7 species
11 fossil species
(Species Checklist)

Gesomyrmex-luzonensisLM4.jpg

Gesomyrmex chaperi

Gesomyrmex luzonensis, worker, head.jpg

Gesomyrmex-tobiasi48Label.jpg

Synonyms
Evolutionary Relationships
Formicinae

Myrmelachistini
  (2 genera)




Lasiini
  (9 genera)




Melophorini
  (9 genera)




Formicini
  (8 genera)






Gesomyrmex
  (7 species)



Oecophylla
  (15 species)




Plagiolepidini
  (10 genera)





Gigantiops, Myrmoteras, Santschiella



Camponotini
  (8 genera)








Based on Ward et al. 2016.

A poorly known resident of tree canopies in Oriental tropics, showing a striking diversity of caste morphologies.

Supersoldier, soldier, workers and brood of Gesomyrmex sp. From Danum, Sabah. Photo © Christopher Wilson

Photo Gallery


Identification

Dubovikov (2004) - The workers of this genus have 8-jointed antennae and soldiers of Gesomyrmex chaperi have 9-jointed antennae (Wheeler, 1916), whereas females have 10-jointed antennae.

Distribution

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

Gesomyrmex Species Richness.png

Biology

From Peeters et al. (2017) Gesomyrmex presents an intriguing division of labour: workers are the active hunters, with very distinct mandibles. Queens (and both kinds of soldiers) have different mandibles, indicating that they do not hunt during colony foundation. However, a foundress needs to chew an entrance tunnel through living wood, and then block this nest entrance for many months until the colony is strong enough to produce the first soldiers. Supersoldiers are presumably reared even later in colony ontogeny, because they are more costly. Relatively few supersoldiers are present and they show two queen-like behaviours: they stay inside nest chambers and block the entrances, and they chew entrance holes when starting other nests belonging to the same colony. Supersoldiers also store nutrients (trophic eggs) in their gaster.

Gesomyrmex nest in the very center of the heartwood in living branches of small diameter. Photo by Decha Wiwatwitaya
To access this secure innermost pith, the founding queen needs to chew an entrance tunnel. Photo by Decha Wiwatwitaya
Gesomyrmex nest entrance. Photo by Decha Wiwatwitaya
Supersoldier head blocking the entrance. Photo by Decha Wiwatwitaya

Dubovikov (2004) - Members of this genus are very rare and ancient forms. The population of their nests are small and they live in small branches of trees (Cole, 1949b). Identification key to five living Gesomyrmex species was published by Cole (1949a).

Castes

In addition to winged queens, three sterile castes can be distinguished using discrete morphological traits, morphometry and total body size (Peeters et al. 2017). Observations of behaviour are challenging in tree canopies, and functional morphology can be used to predict the specialised functions of different castes.


Heads of all four castes of Gesomyrmex sp. shown at different scales (A: worker, B: soldier, C: supersoldier (all from Sabah colony); D: queen from Ulu Gombak). Note differences in ocelli, clypeus, mandibles and frontal lobes (covering the antennal sockets). Photo by Mônica Antunes Ulysséa


Morphology

Worker Morphology

 • Antennal segment count 8 in worker, 10 in queen • Antennal club gradual • Palp formula 6,4 • Total dental count 6-10 • Spur formula 1 simple, 1 simple; 0, 0 • Eyes present • Scrobes absent • Caste polymorphic • Sting absent

Male Morphology

 • Antennal segment count 11 • Antennal club 0 • Palp formula 6,4 • Total dental count 1 (from literature)

Nomenclature

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

  • GESOMYRMEX [Formicinae: Gesomyrmecini]
    • Gesomyrmex Mayr, 1868c: 50. Type-species: †Gesomyrmex hoernesi, by monotypy.
    • Gesomyrmex senior synonym of Gaesomyrmex: Forel, 1893a: 167.
    • Gesomyrmex senior synonym of Dimorphomyrmex: Wheeler, W.M. 1929a: 1.
  • DIMORPHOMYRMEX [junior synonym of Gesomyrmex]
    • Dimorphomyrmex André, 1892b: 49. Type-species: Dimorphomyrmex janeti (junior synonym of Gesomyrmex chaperi), by monotypy.
    • Dimorphomyrmex junior synonym of Gesomyrmex: Wheeler, W.M. 1929a: 1.
  • GAESOMYRMEX [junior synonym of Gesomyrmex]
    • Gaesomyrmex Dalla Torre, 1893: 175, unjustified emendation of Gesomyrmex.
    • Gaesomyrmex junior synonym of Gesomyrmex: Forel, 1893a: 167.

Dubovikov (2004) - The genus Gesomyrmex was established by G. Mayr (1868) for a single species from Baltic amber (Lower Oligocene). The four extant species (Gesomyrmex chaperi, Gesomyrmex howardi, Gesomyrmex kalshoveni and Gesomyrmex spatulatus) are known only from workers. Gesomyrmex luzonensis and Gesomyrmex tobiasi were described from lone queens.

References