Harpegnathos

Harpegnathos is a small ponerine genus of ants found in South and Southeast Asia. They are notable for their jumping ability, complex colony structure, and large to very large workers easily identifiable by their long mandibles and large eyes.[3]

Harpegnathos
Worker H. saltator killing a queen in an inter-colony conflict
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Ponerinae
Tribe: Ponerini
Genus: Harpegnathos
Jerdon, 1851
Type species
Harpegnathos saltator[1]
Jerdon, 1851
Diversity[2]
7 species
Synonyms

Drepanognathus Smith, F., 1858

Taxonomy
Head view of a Harpegnathos saltator worker, showing their characteristic long scythe-shaped mandibles

The genus was established by Thomas C. Jerdon in 1851 to house the single species Harpegnathos saltator, found in India.[4] Believing that the name was unavailable due to homonymy, Smith (1858)[5] incorrectly erected the unnecessary replacement name Drepanognathus (now a synonym of Harpegnathos). For some time, both names were used in publications by other authors until the original name was restored.[3] The most recent species was described in 1963, making the total number of Harpegnathos species seven, with an additional four described subspecies.[2] The genus is closely related to the other genera in its tribe, Ponerini, and is probably a sister to all Ponerini.[3]

Multifunctional mandibles

The ant's mandible exhibits spatially-dependent morphology and bi-axial kinematics, which collectively allows it to perform various daily labors from hunting and attacking to carefully caring for ant eggs.[6] Regarding the spatially-dependent morphology, at the distal-to-middle part, the mandible has double-rowed, non-parallel teeth responsible for powerful clamping. At the proximal part, the mandible has a smooth concavity that is solely used for gently gripping ant eggs.[7] On the other hand, the mandible rotates about two orthogonal axes, changing the mandibular distance and configuration simultaneously.[8] The spatially-dependent morphology and bi-axial kinematics endow the ant mandible multifunctionality.

Hunting behavior

Harpegnathos is an extremely distinctive genus appearance-wise, being very reminiscent of the Myrmecia found in Australia. Like Myrmecia, Harpegnathos has very large eyes, since both hunt mostly by vision and do not lay down pheromone trails like most other ants.[9] Also like Myrmecia, they have large jaws since, owing to their lack of pheromone signals, workers are solitary hunters and must carry food back to the nest in their jaws since they also lack a social stomach.[10]

Colony structure

Harpegnathos has a complex and different colony structure compared to other genera. In the beginning, young winged queens fly out from their natal colony, mate with foreign males and start new colonies independently. What differs from other ants is that, once the short-lived founding queen dies, several daughter workers replace her as reproductives in the colony. Characteristic of several ponerine species, workers can mate (almost always with foreign males) and store sperm in the spermatheca.[3]

In H. saltator, many young workers inbreed with males from the same colony (their brothers). They fight to establish a dominance hierarchy, and a few high-ranking workers become reproductives and lay eggs, so-called gamergates. Every year, new winged queens are reared, and they disperse and start the process again. The combination of queen and gamergate reproduction results in an increased lifespan of colonies, in theory making them immortal.[3][11]

Species
  • Harpegnathos empesoi Chapman, 1963
  • Harpegnathos hobbyi Donisthorpe, 1937
  • Harpegnathos macgregori Wheeler & Chapman, 1925
  • Harpegnathos medioniger Donisthorpe, 1942
  • Harpegnathos pallipes (Smith, 1858)
  • Harpegnathos saltator Jerdon, 1851
  • Harpegnathos venator (Smith, 1858)

References
  1. "Genus: Harpegnathos". antweb.org. AntWeb. Retrieved 13 October 2013.
  2. Bolton, B. (2015). "Harpegnathos". AntCat. Retrieved 5 January 2015.
  3. 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): 1–242. doi:10.11646/zootaxa.3817.1.1. PMID 24943802.
  4. Jerdon, T. C. (1851). "A catalogue of the species of ants found in Southern India". Madras Journal of Literature and Science. 17: 103–127.
  5. Smith, F. (1858). Catalogue of hymenopterous insects in the collection of the British Museum. Part VI. Formicidae. London: British Museum, 216 pp.
  6. Wei, Zhang (2020). "Multifunctional mandibles of ants: Variation in gripping behavior facilitated by specific microstructures and kinematics". Journal of Insect Physiology. 120: 103993. doi:10.1016/j.jinsphys.2019.103993. PMID 31836493. S2CID 209358666.
  7. Wei, Zhang; et, al. (2020). "A mathematical modeling method elucidating the integrated gripping performance of ant mandibles and bio-inspired grippers". Journal of Bionic Engineering. 17 (4): 732–746. doi:10.1007/s42235-020-0065-9. S2CID 220503041.
  8. Wei, Zhang; et, al. (2021). "Double-rowed teeth: design specialization of the H. venator ants for enhanced tribological stability". Bioinspiration & Biomimetics. 16 (5): 055003. doi:10.1088/1748-3190/ac124a. PMID 34233306. S2CID 235768522.
  9. Slone, Jesse D.; Pask, Gregory M.; Ferguson, Stephen T.; Millar, Jocelyn G.; Berger, Shelley L.; Reinberg, Danny; Liebig, Jürgen; Ray, Anandasankar; Zwiebel, Laurence J. (2017). "Functional characterization of odorant receptors in the ponerine ant, Harpegnathos saltator". PNAS. 114 (32): 8586–859. doi:10.1073/pnas.1704647114. PMC 5559025.
  10. Gronenberg, W.; Liebig, J. (1999). "Smaller Brains and Optic Lobes in Reproductive Workers of the Ant Harpegnathos". Naturwissenschaften. 86: 343–345. doi:10.1007/s001140050631.
  11. Peeters, C.; Liebig, J.; Hölldobler, B. (2000). "Sexual reproduction by both queens and workers in the ponerine ant Harpegnathos saltator". Insectes Sociaux. 47 (4): 325–332. doi:10.1007/PL00001724. S2CID 8728206.
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