Onychomyrmex

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Onychomyrmex
Onychomyrmex hedleyi
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Amblyoponinae
Genus: Onychomyrmex
Emery, 1895
Type species
Onychomyrmex hedleyi
Diversity
4 species
(Species Checklist)

Onychomyrmex hedleyi casent0102176 profile 1.jpg

Onychomyrmex hedleyi

Onychomyrmex hedleyi casent0102176 dorsal 1.jpg

Specimen Label

Synonyms
Evolutionary Relationships
Amblyoponinae

Apomyrma
  (1 species)





Prionopelta
  (22 species)




Amblyopone
  (10 species)



Onychomyrmex
  (4 species)






Fulakora
  (25 species)




Adetomyrma
  (9 species), some Stigmatomma




Myopopone
  (1 species), some Stigmatomma





some Stigmatomma



Xymmer
  (2 species)





Mystrium
  (14 species)



some Stigmatomma









Based on Ward & Fisher, 2016. Note that Stigmatomma is not currently monophyletic and some species are more closely related to those of other genera than to each other.

These uncommon ants have an army-ant life style. They alternate between temporary bivouacs in protected sites on the ground and semi-permanent nests in soil or in rotten logs. Groups of workers forage by forming distinct raiding columns across the surface of the ground. Some species are known to be specialist predators on centipedes. Queens have greatly extended gasters (they are dichthadiiform), and new colonies are formed by the division of established colonies.

At a Glance • Ergatoid queen  • Larval Hemolymph Feeding  
 

Identification

The mandibles are long and slender, with numerous (always more than 3) teeth which vary greatly in size and are scattered along the inner margins, and with a sharp, pointed tooth at their tips which is at least 4 times longer than the next longest tooth. The frontal lobes extend only slightly forward of the antennal sockets and do not cover the clypeus when viewed from the front. The petiole has distinct front and upper faces but lacks a rear face, and its attachment to the gaster is broad and approximately the same height as the petiole so that the upper surfaces of the petiole and gaster are separated by at most a shallow impression. The tibiae of the hind legs usually lack spurs at their tips, but when present they are small, straight and not comb-like (pectinate) (best viewed from the front).

Onychomyrmex workers are most often confused with workers of Amblyopone. However, they differ in having the tooth at the tip of the mandible much longer and in lacking a comb-like spur on the hind tibia.

Keys including this Genus

Keys to Species in this Genus

Distribution

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

Onychomyrmex Species Richness.png

Biology

Wheeler (1916) - The species of Onychomyrmex are far from common even in Queensland, and the few colonies I secured were the reward of many hours of search and of the destruction of many old logs in places where I was frequently attacked by land-leeches and saw quite a number of the deadly black snakes (Pseudechis porphyriacus). Perhaps it would be possible for the collector to attract colonies by placing large beetle or cossid larvae in holes in the rotten logs usually found along the paths through the “scrub.”

A study of the worker Onychomyrmex certainly reveals a number of highly specialized characters. Such are particularly the shape of the mandibles, the vestigial condition of the palpi, the small size of the eyes, and the enlargement of the terminal joint, claws, and pulvilli of the middle and hind tarsi. The degenerate visual organs show that these ants belong to the hypogaeic series and that they pass their lives concealed in the logs which gradually decompose in the moist shade of the dense tropical jungle. The powerful, toothed mandibles, long sting and great hooked claws indicate that their possessors do not feed habitually on small feeble insects like termites, but on much larger creatures such as the larvae of passalids and scarabaeids and possibly on adult myriopods and scorpions. This I found to be the case in a colony of O. mjobergi, for when the log containing it was broken open, many of the workers were detected in the act of biting and stinging to death a huge lamellicorn beetle larva more than two inches in length, which they had just found in a cavity in the wood. It is not improbable that the colonies move from place to place in search of their prey, like the colonies of the subterranean Dorylinae (Eciton coecum and Dorylus), which they very closely resemble in behavior, color, sculpture, and pilosity.

Castes

Morphology

Worker Morphology

 • Antennal segment count 12 • Antennal club gradual • Palp formula 2,2 • Total dental count 9-10 • Spur formula 1 simple, 1 simple; 0, 0 • Sting present

Male Morphology

 • Antennal segment count 13 • Antennal club 0 • Palp formula 2,2 • Total dental count 1-2 (from literature)

Nomenclature

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

  • ONYCHOMYRMEX [Amblyoponinae]
    • Onychomyrmex Emery, 1895g: 349. Type-species: Onychomyrmex hedleyi, by monotypy.
  • LITHOMYRMEX [junior synonym of Stigmatomma]
    • Lithomyrmex Clark, 1928a: 30. Type-species: Lithomyrmex glauerti, by original designation.
    • Lithomyrmex junior synonym of Amblyopone: Brown, 1960a: 156.
    • Lithomyrmex junior synonym of Stigmatomma: Yoshimura & Fisher, 2012:17.
    • Lithomyrmex junior synonym of Onychomyrmex: Ward & Fisher, 2016: 691.

Wheeler (1916):

Worker

Small, slender, monomorphic. Mandibles rather long, narrow at the base, broadest in the middle, with long, curved, acute tips, their inner borders armed with a number of unequal teeth, some of which, near the middle of the series, are directed backward. Both the maxillary and labial palpi very short, 2-jointed. Clypeus very short, abrupt, with rounded, entire anterior border beset with a regular row of minute teeth. Frontal carinae small, prominent, closely approximated, enlarged and dilated anteriorly, separated by a very narrow groove. Frontal groove lacking. Eyes very small, consisting of about 6 or 8 ommatidia, situated behind the middle of the head. Antennae 12-jointed, funiculus filiform, not clavate or conspicuously enlarged at the tip. Thorax slender, with very distinct promesonotal and mesoepinotal sutures; mesonotum smull, digeoidal, with distinet sutures on all sides. Petiole with a short peduncle in front and a large, prominent compressed ventral projection, the node rounded, scarcely narrowed behind where it articulates by means of its whole posterior surface with the postpetiole. Postpetiole large, convex below, separated by a pronounced constriction from the gaster, which is rather short. Sting very long and well-developed. Legs long; middle and hind tibiae without spurs; terminal joints of the middle and hind tarsi conspicuously elongated and incrassated, with very large, strongly curved, simple claws and large pulvilli.

Queen

Apterous and ergatoid. Head broadened in front and more depressed at the anterior corners than in the worker. Eyes very small; ocelli absent. Mandibles more falcate, not abruptly curved at the tips, with only a few short, blunt teeth. Mesonotum somewhat longer than in the worker. Petiole differing from that of the worker in being much broader, with a very short and narrow peduncle and lacking the ventral projection. Constriction between the postpetiole and gaster much less distinct than in the worker. Gaster much larger, elongate elliptical, sting somewhat smaller. In other respects like the worker.

Larva

Slender, smooth and nontuberculate, with twelve very distinct postcephalic segments, the constrictions between which are everywhere deep and conspicuous, even at the posterior end of the body. Head short, rounded, with well-developed, slender, acute, falcate mandibles, destitute of teeth. Clypeus rather long, projecting. Antennae very small. Maxillary sensillae long and prominent. Head sparsely, remainder of body more densely and uniformly covered with short, straight, stiff hairs or bristles.

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 382, Onychomyrmex in Ponerinae, Onychomyrmicini)
  • Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 156, Onychomyrmex in Amblyoponinae, Amblyoponini)
  • Brown, W. L., Jr. (1950) Morphological, taxonomic, and other notes on ants. Wasmann Journal of Biology, 8: 241–250.
  • Brown, W. L., Jr. (1960) Contributions toward a reclassification of the Formicidae. III. Tribe Amblyoponini (Hymenoptera). Bulletin of the Museum of Comparative Zoology, 122: 143–230.
  • Donisthorpe, H. 1943g. A list of the type-species of the genera and subgenera of the Formicidae. [part]. Ann. Mag. Nat. Hist. 11(10): 617-688 (page 678, Onychomyrmex in Ponerinae, Ponerini (anachronism))
  • Emery, C. 1895h. Descriptions de quelques fourmis nouvelles d'Australie. Ann. Soc. Entomol. Belg. 39: 345-358 (page 349, Onychomyrmex as genus)
  • Emery, C. 1911e. Hymenoptera. Fam. Formicidae. Subfam. Ponerinae. Genera Insectorum 118: 1-125 (page 96, Onychomyrmex in Ponerinae, Ponerini [subtribe Onychomyrmicini])
  • Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 235, Onychomyrmex in Ponerinae, Amblyoponini)
  • Hölldobler, B., Engel, H., Taylor, R. W. (1982) A new sternal gland in ants and its function in chemical communication. Naturwissenschaften, 69: 90–91.
  • Hölldobler, B., Palmer, J. M. (1989) A new tarsal gland in ants and the possible role in chemical communication. Naturwissenschaften, 76: 385–386.
  • Miyata H, Shimamura T, Hirosawa H, Higashi S. 2003. Morphology and phenology of the primitive ponerine army ant Onychomyrmex hedleyi (Hymenoptera: Formicidae) in a highland rainforest of Australia. Journal of Natural History 37: 115–125.
  • Ward, P.S. & Fisher, B.L. 2016. Tales of dracula ants: the evolutionary history of the ant subfamily Amblyoponinae (Hymenoptera: Formicidae). Systematic Entomology, 41, 683–693 (DOI: 10.1111/syen.12186).
  • Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 135, Onychomyrmex in Ponerinae, Ponerini)
  • Wheeler, W. M. 1916a. The Australian ants of the genus Onychomyrmex. Bulletin of the Museum of Comparative Zoology. 60:45-54.