Rhopalomastix

Rhopalomastix
Rhopalomastix rothneyi
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Crematogastrini
Genus:	Rhopalomastix Forel, 1900
Type species
Rhopalomastix rothneyi
Diversity
11 species (Species Checklist, Species by Country) Rhopalomastix rothneyi Specimen Label

Evolutionary Relationships

Rostromyrmex Cardiocondyla Ocymyrmex Nesomyrmex Xenomyrmex Terataner Atopomyrmex Cataulacus Carebara Diplomorium Melissotarsus Rhopalomastix Calyptomyrmex Tetramorium Cyphoidris Dicroaspis Aretidris Vollenhovia Dacetinops Indomyrma Crematogaster Meranoplus Lophomyrmex Adlerzia Recurvidris Stereomyrmex Trichomyrmex Eutetramorium Royidris Malagidris Vitsika Huberia Podomyrma Liomyrmex Metapone Kartidris Mayriella Tetheamyrma Dacatria Proatta Dilobocondyla Secostruma Acanthomyrmex Myrmecina Perissomyrmex Pristomyrmex some Lordomyrma Propodilobus Lasiomyrma [some Lordomyrma Ancyridris some Lordomyrma Paratopula Poecilomyrma Romblonella Rotastruma Gauromyrmex Vombisidris Temnothorax Harpagoxenus Formicoxenus Leptothorax

Based on Ward et al. (2014) and Blaimer et al. (2018).

Rhopalomastix workers chew a network of tunnels under the bark of living trees where they nest. Tunnels are inhabited by large numbers of diaspidid scale insects (Yong et al. 2019). Non-specific associations with different genera of trees and diaspidids were recorded in SIngapore, Thailand and Okinawa (Japan) (C. Peeters unpublished). Rhopalomastix is the second ant genus involved in a mutualism with diaspidids, besides Melissotarsus.

Eguchi, Bui and Yamane (2011) - The worker of Rhopalomastix is easily separated from those of other known Vietnamese myrmicine genera by a combination of the following characters: frontal lobes closely approximated; eye relatively large; mesosoma box-shaped; fore- and hindfemora extremely widened and flattened distally; postpetiole broadly attached to gaster.

Keys including this Genus

• Key to Australian Genera of Myrmicinae
• Key to Vietnamese Myrmicinae Genera

 

Biology

Yong et al. (2019) - The presence of diaspidid scale insects inside all nests examined is a strong suggestion that they are a source of food for the ants. However, there are no direct observations of feeding or other interactions because ants stop normal activities and take cover as soon as the tunnels are opened. The five genera of diaspidids associated with four species of Rhopalomastix in Singapore all share the remarkable characteristic that females can reach sexual maturity without secreting a hard wax shield. As in Melissotarsus, Rhopalomastix adult females can secrete silk that is used to secure the tunnels. In contrast, Rhopalomastix workers have a sting and lack the extreme leg specialisation legs,

Workers and one larva of Rhopalomastix murphyi together with naked diaspidid Andaspis numerata in galleries chewed under the bark. Note a few scattered shields of different sizes. From Singapore. Photo by Chui Shao Xiong.

Eggs of Rhopalomastix johorensis amid an aggregation of Rhopalaspis peetersi adult female diaspidids and eggs. One naked diaspidid is in the process of ovipositing. From Singapore. Photo by Gordon Yong.

Diaspidid scale insects inside tunnels chewed in live wood by Rhopalomastix workers. Bark has been removed to expose the tunnels. From Thailand. Photo by Christian Peeters.

Rhopalomastix workers and larvae inside tunnels chewed in live wood, together with diaspidids (right). From Thailand. Photo by Christian Peeters.

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Morphology

Worker Morphology

• Antennal segment count: 10
• Antennal club: 2
• Palp formula: 1,1; 0,1
• Total dental count: 2-4
• Spur formula: 0, 0
• Sting: present

Male Morphology

 • Antennal segment count 12 • Antennal club gradual • Palp formula 1,1 • Total dental count 0 • Spur formula 0, 0

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• RHOPALOMASTIX [Myrmicinae: Melissotarsini]
  • Rhopalomastix Forel, 1900a: 24. Type-species: Rhopalomastix rothneyi, by monotypy.

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

Eguchi, Bui and Yamane (2011) - The worker of the single Vietnamese species has the following features. Worker monomorphic; head subrectangular; frontal carina and antennal scrobe absent; frontal lobes touching or separated only by a narrow longitudinal impression; median portion of clypeus weakly convex anteriorly, lacking median clypeal seta but bearing a pair of thick and short submedian setae; mandible small, with 4 teeth; antenna 10-segmented, with 2-segmented club; scape very short, extending a little beyond midlength of head when laid backwards; eye relatively large, located well in front of midlength of side of head; mesosoma box-shaped; promesonotal suture absent dorsally; metanotal groove absent; propodeum unarmed; metapleural gland bulla large; propodeal lobe absent; fore- and hindfemora extremely widened and flattened distally; petiole nodiform, with relatively high node, anteroventrally with well-developed subpetiolar process; postpetiole much shorter than high, broadly attached to anteriormost portion of gaster; gastral shoulder absent.

References

• Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 258, Rhopalomastix in Myrmicinae, Melissotarsini)
• Bouju, V., Perrichot, V. 2020. A review of amber and copal occurrences in Africa and their paleontological significance. BSGF - Earth Sciences Bulletin 191, 17 (doi:10.1051/bsgf/2020018).
• Eguchi, K., Bui, T.V. & Yamane, S. 2011. Generic synopsis of the Formicidae of Vietnam. Part 1 – Myrmicinae and Pseudomyrmecinae. Zootaxa 2878: 1-61.
• Emery, C. 1914e. Intorno alla classificazione dei Myrmicinae. Rend. Sess. R. Accad. Sci. Ist. Bologna Cl. Sci. Fis. (n.s.) 18: 29-42 (page 40, Rhopalomastix in Myrmicinae, Melissotarsini)
• Emery, C. 1922c. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [part]. Genera Insectorum 174B: 95-206 (page 118, Rhopalomastix in Myrmicinae, Melissotarsini)
• Forel, A. 1900a. Un nouveau genre et une nouvelle espèce de Myrmicide. Ann. Soc. Entomol. Belg. 44: 24-26 (page 24, Rhopalomastix as genus)
• Forel, A. 1917. Cadre synoptique actuel de la faune universelle des fourmis. Bull. Soc. Vaudoise Sci. Nat. 51: 229-253 (page 242, Rhopalomastix in Myrmicinae, Melissotarsini)
• Wang, W.Y., Yong, G.W.J., Jaitrong, W. 2018. The ant genus Rhopalomastix (Hymenoptera: Formicidae: Myrmicinae) in Southeast Asia, with descriptions of four new species from Singapore based on morphology and DNA barcoding. Zootaxa 4532:301-340 (DOI 10.11646/zootaxa.4532.3.1).
• Wheeler, W. M. 1910b. Ants: their structure, development and behavior. New York: Columbia University Press, xxv + 663 pp. (page 140, Rhopalomastix in Myrmicinae, Solenopsidini)
• 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 661, Rhopalomastix in Myrmicinae, Melissotarsini)
• Wheeler, W. M. 1929. The ant genus Rhopalomastix. Psyche (Camb.) 36: 95-101. (page 95, Review of genus)
• Xu, Z. 1999a. Systematic studies on the ant genera of Carebara, Rhopalomastix and Kartidris in China (Hymenoptera: Formicidae: Myrmicinae). Acta Biol. Plateau Sin. 14: 129-136 (page 130, China species key)
• Yong G, Matile-Ferrero D & Peeters C 2019. Rhopalomastix is only the second ant genus known to live with diaspidid scale insects. Insectes Sociaux 66: 273–282.