Polyrhachis laboriosa

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Polyrhachis laboriosa
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Camponotini
Genus: Polyrhachis
Subgenus: Myrma
Species group: militaris
Species: P. laboriosa
Binomial name
Polyrhachis laboriosa
Smith, F., 1858

Polyrhachis laboriosa casent0217777 p 1 high.jpg

Polyrhachis laboriosa casent0217777 d 1 high.jpg

Specimen Labels

Synonyms

A common West African species common in forests and forest edge. P. laboriosa builds its nests on the underside of leaves. Both its abundance and workers with golden-coloured gaster, has meant this species has garnered attention from numerous myrmecologists.

Identification

A member of the Polyrhachis militaris species-group. Bolton (1973) - A member of the militaris-group, laboriosa is easily separated from all other species by the unique form of the petiole.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Angola, Cameroun, Congo, Democratic Republic of Congo, Equatorial Guinea, Ghana, Ivory Coast, Nigeria, Sierra Leone (type locality), Togo, Uganda.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Nesting Habits

P. laboriosa lives in pioneer trees and shrubs on forest edges in West Africa (Lenoir & Dejean 1994). Nests are built at a height of 2-3m in the canopy of small trees, using living leaves and plant debris. There is great diversity in the architecture of these nests, showing high opportunism by the ants. Leaves are incorporated in the nests, and provide structural strength for the carton. P. laboriosa belongs to the subgenus Myrma, in which there is no weaving using larval silk. The use of spider silk for nest construction has been described for P. laboriosa (Collart 1932). J.-L. Mercier (unpublished) observed a worker collecting silk from a spider web on a leaf surface. The ant pulled on the silk strands one by one, and rolled them into a ball using her gaster. During this time, the spider stood about 5cm away, and once attempted to chase the ant. At the end, the worker carried the silk to her nest that was being constructed by about 10 nestmates.

Founding queens have been observed retrieving various vegetal material which was used to build a small cell under a leaf (Lenoir & Dejean 1994). Two of 18 foundations involved two queens.

Nest of P. laboriosa made of a leaf bent and stitched together with vegetal debris and spider silk. Photo by Patrick Landmann.

Foraging for plant secretions and small prey or insect corpses is done mostly by single workers orientating visually, although chemical recruitment occurs when larger food sources are exploited (Mercier & Lenoir 1999).

61 nests censused near Yaoundé (Cameroon) yielded an average of 400 workers per nest (range 25-1919). Only 21% of nests had a dealated fertile queen, and such nests were more populous (881±505 workers, N=12) than queenless nests (277.5±263 workers, N=44) (J.-L. Mercier, unpublished). Five nests collected in Dja Reserve (Cameroon) contained 63-457 workers and up to 259 worker cocoons; a dealate queen was present in only one nest (K. Yéo & C. Peeters, unpublished). These data suggest that P. laboriosa colonies are polydomous (i.e. distributed into several nests) and monogynous (single queen).

Nest constructed under a leaf, cut open to reveal inner partitions built with carton. From Dja Reserve, Cameroon. Photo by Patrick Landmann.

Bolton (1973) - The nests of this species, common in West Africa, are well known and consist of a mixture of vegetable fragments and small twigs bound together by silk and fungal hyphae, and adherent to the undersides of leaves or situated at the fork of small branches. Form and construction of the nest have been discussed many times, for example by Wheeler (1922a:259), Santschi (1909:393) and Collart (1932). P. laboriosa appears to be restricted to forested areas. When disturbed the workers curve the gaster under the alitrunk to eject formic acid, and also tap the gaster upon the substrate, making a rattling noise when performed by a number of workers together. If individual arboreal foragers are disturbed they tend to release their grip on the bark and fall into the undergrowth.

Alate females have been recorded as follows, GHANA : July, September. CONGO (KINSHASA) : March, August.

Fungi

This species is a host for the fungus Ophiocordyceps unilaterialis (a pathogen) (Shrestha et al., 2017).

Castes

Winged gyne of P. laboriosa from Dja Reserve, Cameroon. Photo by Patrick Landmann.
Worker of P. laboriosa from Dja Reserve, Cameroon. Photo by Patrick Landmann.
Caste difference in body size is slight in P. laboriosa: dealate queen (left) and worker (right). Photo by Patrick Landmann.

Nomenclature

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

  • laboriosa. Polyrhachis laboriosus Smith, F. 1858b: 72, pl. 4, figs. 21, 22 (w.) SIERRA LEONE. Mayr, 1896: 250 (q.m.); Wheeler, G.C. & Wheeler, J. 1953e: 207 (l.). Combination in P. (Myrma): Santschi, 1914d: 384. Senior synonym of architecta, hortulana: Bolton, 1973b: 308.
  • architecta. Polyrhachis (Myrma) laboriosa var. architecta Santschi, 1924b: 224 (w.) DEMOCRATIC REPUBLIC OF CONGO. Junior synonym of laboriosa: Bolton, 1973b: 308.
  • hortulana. Polyrhachis (Myrma) hortulana Arnold, 1955: 735, fig. 3 (w.) UGANDA. Junior synonym of laboriosa: Bolton, 1973b: 308.

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

Description

Worker

Bolton (1973) - TL 10.2-11.6, HL 2.15-2.25, HW 1.56-1.81, CI 71-79, SL 2.85-3.34, SI 182-196, PW 1.19-1.36, MTL 3.26-4.11. (30 measured.)

Anterior clypeal margin arcuate, entire, the clypeus with a distinct median, longitudinal carina. Eyes strongly convex, the sides of the head behind the eyes strongly convergent to a short convex occipital margin. Alitrunk marginate throughout its length, interrupted by impressions at the sutures. Pronotum and propodeum weakly concave transversely, the former armed with a pair of long acute, divergent spines, the latter with a pair of small teeth. Promesonotal suture distinct, metanotal groove impressed. In profile the propodeum rises abruptly from the metanotal groove, behind which it slopes convexly to the propodeal teeth. Petiole armed with a single pair of spines, set at the dorsolateral corners of the scale, weakly divergent, their apices strongly hooked, directed posteriorly and somewhat laterally.

All dorsal surfaces of head, alitrunk and gaster with numerous erect hairs, varying in colour from grey to golden-yellow. Pubescence dense, mostly hiding the sculpturation on the gaster, usually grey on the head and alitrunk, golden or bronzy on the gaster, but sometimes the pubescence of the pronotal dorsum is also yellow or golden.

Head reticulate-punctuate except on the vertex where the sculpturation is of longitudinal rugulation. Pronotal dorsum superficially reticulate-punctate, the mesonotum and propodeum usually more coarsely sculptured, rugulose or more strongly reticulate-punctate; the sculpturation of the pronotum may be concealed by the pubescence. Gaster finely reticulate-punctate, mostly hidden by the dense pubescence.

Queen

Bolton (1973) - As worker, larger, with the marginations of the alitrunk less distinct. Pronotal spines and propodeal teeth reduced, the latter often to a pair of tubercles.

Type Material

Bolton (1973) - Holotype worker, SIERRA LEONE (D. F. Morgan) (The Natural History Museum) [examined].

References

References based on Global Ant Biodiversity Informatics

  • André E. 1887. Description de quelques fourmis nouvelles ou imparfaitement connues. Rev. Entomol. (Caen) 6: 280-298.
  • Arnold G. 1955. New species of African Hymenoptera. No. 11. Occasional Papers of the National Museum of Southern Rhodesia. 2: 733-762.
  • Bernard F. 1953. La réserve naturelle intégrale du Mt Nimba. XI. Hyménoptères Formicidae. Mémoires de l'Institut Français d'Afrique Noire 19: 165-270.
  • Bolton B. 1973. The ant genus Polyrhachis F. Smith in the Ethiopian region (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology 28: 283-369.
  • Dejean A., F. Azemar, R. Cereghino, M. Leponce, B. Corbara, J. Orivel, and A. Compin. 2015. The dynamics of ant mosaics in tropical rainforests characterized using the SelfOrganizing Map algorithm. Insect Science doi: 10.1111/1744-7917.12208
  • Eidmann H. 1944. Die Ameisenfauna von Fernando Poo. 27. Beitrag zu den Ergebnissen der Westafrika-Expedition. Zool. Jahrb. Abt. Syst. Ökol. Geogr. Tiere 76: 413-490.
  • Emery C. 1892. Voyage de M. Ch. Alluaud dans le territoire d'Assinie (Afrique occidentale) en juillet et août 1886. Formicides. Annales de la Société Entomologique de France 60: 553-574.
  • Fisher B. L. 2004. Diversity patterns of ants (Hymenoptera: Formicidae) along an elevational gradient on Monts Doudou in southwestern Gabon. Memoirs of the California Academy of Sciences 28: 269-286.
  • Forel A. 1886. Études myrmécologiques en 1886. Annales de la Société Entomologique de Belgique. 30: 131-215.
  • IZIKO South Africa Museum Collection
  • Lévieux J. 1972. Les fourmis de la savane de Lamto (Côte d'Ivoire): éléments de taxonomie. Bulletin de l'Institut Fondamental d'Afrique Noire. Série A. Sciences Naturelles 34: 611-654.
  • Medler J. T. 1980: Insects of Nigeria - Check list and bibliography. Mem. Amer. Ent. Inst. 30: i-vii, 1-919.
  • Radoszkowsky O. 1881. Hymenoptères d'Angola. Jornal de Sciencias Mathematicas, Physicas e Naturaes 8(31): 197-221.
  • Robson Simon Database Polyrhachis -05 Sept 2014
  • Santschi F. 1910. Formicides nouveaux ou peu connus du Congo français. Annales de la Société Entomologique de France 78: 349-400.
  • Santschi F. 1933. Contribution à l'étude des fourmis de l'Afrique tropicale. Bulletin et Annales de la Société Entomologique de Belgique. 73: 95-108.
  • Stitz H. 1910. Westafrikanische Ameisen. I. Mitteilungen aus dem Zoologischen Museum in Berlin 5: 125-151.
  • Tadu Z., C. Djieto-Lordon, R. Babin, Yede, E. B. Messop-Youbi, and A. Fomena. 2013. Influence of insecticide treatment on ant diversity in tropical agroforestry system: some aspect of the recolonization process. International Journal of Biodiversity and Conservation 5(12): 832-844.
  • Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. II. The ants collected by the American Museum Congo Expedition. Bulletin of the American Museum of Natural History 45: 39-269.
  • Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004
  • Yeo K., and A. Hormenyo. 2007. A Rapid Survey of Ants in Ajenjua Bepo and Mamang River Forest Reserves, Eastern Region of Ghana. Pp 27-29. In McCullough, J., P. Hoke, P. Naskrecki, and Y. Osei-Owusu (eds.). 2008. A Rapid Biological Assessment of the Ajenjua Bepo and Mamang River Forest Reserves, Ghana. RAP Bulletin of Biological Assessment 50. Conservation International, Arlington, VA, USA.