Rotastruma

Rotastruma
Rotastruma recava
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Crematogastrini
Genus:	Rotastruma Bolton, 1991
Type species
Rotastruma recava
Diversity
2 species (Species Checklist, Species by Country) Rotastruma recava Specimen Label

Evolutionary Relationships

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).

Luo and Guénard (2016) - Rotastruma is a rarely collected arboreal genus with two species. They exhibit a limited distribution in the Indomalayan region. Rotastruma recava is known from Borneo and the Malaysian Peninsula, and Rotastruma stenoceps is reported from China (Hubei, Hunan, Guangdong, Yunnan) (antmaps.org). The latter was described in 1991 from Guangdong (China) on the basis of the worker caste, with virtually no information reported on its ecology since its original description. Recently, during attempts to collect additional Paratopula specimens, a single queen identified as Rotastruma stenoceps was collected in Hong Kong, less than 200 kilometres South East from the site of the holotype (Bolton 1991).

Identification

Rotastruma is a marginal leptothoracine genus. It falls into an assemblage of small and little-understood genera on the periphery of what is currently understood as tribe Leptothoracini. Rotastruma appears to have affinities with the genera Paratopula and Romblonella, which form part of this marginal group. Little more can be said of this enigmatic small genus until a detailed survey can be made to define with some accuracy where the limits of tribe Leptothoracini really lie. The respective species pages of the ants that comprise this genus explain how to identify the two known species.

Keys including this Genus

• Key to Vietnamese Myrmicinae Genera

 

Distribution

Southern China, Singapore and Sarawak (East Malayasia).

Biology

Little is known about the two species of Rotastruma. R. recava has been collected from dead twigs. R. stenoceps is only known from the types and there are no habitat or other biological details associated with their collection.

Hosoishi et al. (2015) collected one colony of an uncertain Rotastruma sp. in regrowth forest in Kampong Thom Province, Cambodia. Two species are currently recognised: Rotastruma recava from Singapore and Borneo, and Rotastruma stenoceps from China (Bolton, 1991). According to a key to species (Bolton, 1991), the collected specimens are similar to R. stenoceps in having the occipital margin transverse and sides of head straight, but differ slightly by having propodeal spines curving upward.

Morphology

Worker Morphology

• Antennal segment count: 12
• Antennal club: 3
• Palp formula: 5,3
• Spur formula: 0, 0
• Sting: present

Male Morphology

 • Caste unknown

Nomenclature

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

• ROTASTRUMA [Myrmicinae: Formicoxenini]
  • Rotastruma Bolton, 1991: 8. Type-species: Rotastruma recava, by original designation.

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

Worker Monomorphic subarboreal to arboreal myrmicine ants with the following combination of characters.

1. Palp formula 5, 3.

2. Mandible triangular, with 6 teeth which decrease in size from apical to basal.

3. Clypeus with a median longitudinal carina; anterior clypeal margin with a pair of hairs which straddle the midpoint.

4. Median portion of clypeus broad posteriorly, broadly inserted between the frontal lobes.

5. Frontal lobes narrow, each lobe distinctly narrower than the portion of the clypeus that is inserted between them.

6. Torulus not freely projecting.

7. Frontal carinae very weakly present; antennal scrobes represented only by extremely shallowly depressed areas running above the eyes.

8. Eyes large, situated at or just behind the midlength of the sides.

9. Antennae 12-segmented, the 3 apical segments forming a strongly defined club.

10. Alitrunk low in profile and with a shallowly evenly convex dorsum; promesonotum not domed-convex; metanotal groove absent; propodeum bispinose; sides of alitrunk marginate, especially on mesonotum and propodeum.

11. Propodeal spiracle set low on the side at about the midlength of the sclerite, very close to the dorsalmost point of the metapleural gland bulla.

12. Metapleural lobes present, small and rounded.

13. Metasternal process absent; cuticle between anterior halves of metacoxal cavities depressed.

14. Tibial spurs absent from middle and hind legs.

15. Petiole nodiform, with a short anterior peduncle; petiolar spiracle located at about the midlength of the peduncle.

16. Postpetiolar sternite reduced, small in profile.

17. Sting functional, strong and simple.

18. Cuticle thick and armoured. Pilosity present on all dorsal surfaces of head and body.

Female As worker but only very slightly larger in size. Ocelli present. Alitrunk with full complement of flight sclerites and certainly winged when virgin.

References

• Bolton, B. 1991. New myrmicine genera from the Oriental Region (Hymenoptera: Formicidae). Syst. Entomol. 16: 1-13. (page 8, Rotastruma as genus; Rotastruma in Myrmicinae, Leptothoracini)
• Bolton, B. 1994. Identification guide to the ant genera of the world. Cambridge, Mass.: Harvard University Press, 222 pp. (page 105, Rotastruma in Myrmicinae, Formicoxenini)
• Bolton, B. 1995a. A taxonomic and zoogeographical census of the extant ant taxa (Hymenoptera: Formicidae). J. Nat. Hist. 2 29: 1037-1056 (page 1052, Rotastruma in Myrmicinae, Formicoxenini)
• Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 382, Rotastruma in Myrmicinae, Formicoxenini)
• Bolton, B. 2003. Synopsis and Classification of Formicidae. Mem. Am. Entomol. Inst. 71: 370pp (page 252, Rotastruma in Myrmicinae, Formicoxenini)
• Luo, Y.Y. and Guénard, B. 2016. Descriptions of a new species and the gyne in the rarely collected arboreal genera Paratopula and Rotastruma (Hymenopytera: Formicidae) from Hong Kong, with a discussion on their ecology. Asian Myrmecology. 8:1-16. doi:10.20362/am.008016