Tetramorium decem

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Tetramorium decem
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Tetramorium
Species: T. decem
Binomial name
Tetramorium decem
Forel, 1913

Decamorium decem casent0415619 profile 1.jpg

Decamorium decem casent0415619 dorsal 1.jpg

Specimen Label

Based on Arnold (1917) and specimens from Arabuko Sokoke, T. decem nests in sandy soil. They preys on termites.

Identification

Hita Garcia & Fisher (2014) - A member of the Tetramorium decem species group. Tetramorium decem can be recognised by the following combination of characters: relatively larger species (HW 0.59–0.62; WL 1.02–1.16); propodeal teeth relatively longer (PSLI 17–19); petiolar node in profile around 1.2 to 1.3 times higher than long (LPeI 77–82); dorsum of promesonotum unsculptured, smooth, and very shiny; strongly bicoloured species with dark brown or black gaster contrasting with light brown to reddish brown remainder of body.

Tetramorium decem is the core species of the group (Tetramorium decem species group), and was the type species for the description of the subgenus Decamorium by Forel (1913a). It is perhaps the most conspicuous species of the group. Its bicolouration, larger size, lack of sculpture on the mesosomal dorsum, and a higher petiolar node render it immediately recognisable. The mostly unsculptured, smooth and shiny mesosomal dorsum distinguishes T. decem from Tetramorium raptor and Tetramorium uelense, in which the dorsum of the mesosoma is clearly longitudinally rugose/rugulose. Tetramorium ultor and Tetramorium venator both share the lack of sculpture on the mesosomal dorsum with T. decem, but can still be easily separated from the latter. Tetramorium decem is generally larger in size (WL 1.02–1.16), has longer propodeal spines (PSLI 17–19) and is also conspicuously bicoloured, whereas T. ultor and T. venator are smaller species (WL 0.85–0.98) with significantly shorter propodeal teeth (PSLI 9–13) and a more uniform brown to black body colouration. In addition, T. decem also has a higher petiolar node, in profile around 1.2 to 1.3 times higher than long (LPeI 77–82), compared to the other two, in which the node in profile is only around 1.0 to 1.2 times higher than long (LPeI 86–100). The species that appears to be morphologically closest to T. decem is T. uelense. Both species share the large body, bicolouration, and preference for arid habitats. However, in addition to the sculpture on the mesosoma, T. uelense also has a lower petiolar node, in profile around 1.1 times higher than long (LPeI 88–93). Another character that is shared between T. decem and T. uelense but absent in the other species of the group is the development of the ventral margin of the antennal scrobe. In T. raptor, T. ultor, and T. venator the margin is clearly and well defined, while in T. decem and T. uelense it is less so and merges more with the surrounding rugose sculpture.

Based on the available material we did not observe any significant form of intraspecific variation in T. decem.

Keys including this Species

Distribution

Hita Garcia & Fisher (2014) - Based on the redefined species definition, T. decem is only known from the type locality in Zimbabwe and two additional localities in East Africa: Arabuko Sokoke in Kenya and Mkomazi in Tanzania. Nevertheless, if more extensive sampling efforts are undertaken in East Africa, T. decem is likely to be found in more localities in Kenya, Tanzania, and Zimbabwe.

Latitudinal Distribution Pattern

Latitudinal Range: -0.317° to -25.9494°.

   
North
Temperate
North
Subtropical
Tropical South
Subtropical
South
Temperate

Distribution based on Regional Taxon Lists

Afrotropical Region: Ivory Coast, Kenya, United Republic of Tanzania, Zimbabwe (type locality).

Distribution based on AntMaps

AntMapLegend.png

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.
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Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.
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Habitat

Like Tetramorium uelense and Tetramorium ultor, T. decem prefers arid habitats, such as savannah and woodland.

Biology

Hita Garcia and Fisher (2014) - If one considers the whole tribe Tetramoriini, then it becomes apparent that the specialized habitus of Decamorium is not unique. Several authors have stated that Decamorium (now synonymized with Tetramorium) are specialised termite hunters, and that their specialised morphology could be an adaptation to such a dangerous lifestyle (Arnold 1917; Bolton 1976; Longhurst et al. 1979). Interestingly, both Arnold (1917) in the original description and later Bolton (1980) noted the similarities in general body shape and diet between members of Decamorium and the species Tetramorium simulator from South Africa. We agree that the similarities in morphology are indeed obvious, especially in profile view. However, at present it is not clear whether the shared morphology is based on a close phylogenetic relationship between Decamorium and T. simulator or a result of convergent evolution due to a similar lifestyle hunting termites. We believe the latter more likely since the twelve-segmented antennae, the much broader head, and sculptured clypeus of T. simulator suggest a closer relationship to another group with twelve-segmented antennae than to Decamorium. Therefore, we hypothesise that both have evolved from different Tetramorium lineages and acquired the specialised habitus independently from each other. Another remarkable aspect is the lack of a strong and sharp clypeal shield in T. simulator, which seems to have been reduced in a manner almost similar, though less pronounced, to Decamorium.

Castes

Worker

MCZ ENT Decamorium decem 001hef.jpgMCZ ENT Decamorium decem 001hal.jpgMCZ ENT Decamorium decem 001had.jpgMCZ ENT Decamorium decem 001lbs.jpg
. Owned by Museum of Comparative Zoology.

Nomenclature

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

  • decem. Tetramorium (Decamorium) decem Forel, 1913a: 121 (w.) ZIMBABWE. Arnold, 1917: 350 (q.m.). Combination in Decamorium: Wheeler, W.M. 1922a: 906; in Tetramorium: Hita Garcia & Fisher, 2014: 78.

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

Description

Worker

Hita Garcia & Fisher (2014) - (N=15). HL 0.71–0.74 (0.72); HW 0.59–0.62 (0.60); SL 0.42–0.45 (0.43); EL 0.19–0.21 (0.20); PH 0.33–0.37 (0.35); PW 0.47–0.50 (0.48); WL 1.02–1.16 (1.06); PSL 0.12–0.14 (0.13); PTL 0.25–0.27 (0.26); PTH 0.31–0.34 (0.33); PTW 0.22–0.24 (0.23); PPL 0.24–0.27 (0.25); PPH 0.32–0.36 (0.34); PPW 0.32–0.36 (0.34); CI 83–85 (84); SI 70–76 (72); OI 32–34 (33); DMI 41–47 (45); LMI 32–34 (33); PSLI 17–19 (18); PeNI 46–51 (48); LPeI 77–82 (80); DPeI 85–92 (88); PpNI 67–76 (70); LPpI 71–77 (75); DPpI 128–138 (133); PPI 143–149 (147).

Head much longer than wide (CI 83–85); posterior head margin weakly concave. Anterior clypeal margin with distinct, but often shallow median impression. Frontal carinae strongly developed and noticeably raised forming dorsal margin of very well-developed antennal scrobes, curving down ventrally and anteriorly halfway between posterior eye margin and posterior head margin and forming posterior and parts of ventral scrobe margins; antennal scrobes very well developed, deep and with clearly defined margins, but ventral margin less strongly developed, median scrobal carina absent. Antennal scapes short, not reaching posterior head margin (SI 70–76). Eyes very large (OI 32–34). Mesosomal outline in profile flat to weakly convex, relatively low and elongate (LMI 32–34), moderately to strongly marginate from lateral to dorsal mesosoma; promesonotal suture absent; metanotal groove present, distinct, and clearly impressed. Propodeal spines short, elongate-triangular, and moderately acute (PSLI 17–19), propodeal lobes short, triangular, and usually blunt, always significantly shorter than propodeal spines. Tibiae and femorae strongly swollen. Petiolar node nodiform with moderately rounded antero- and posterodorsal margins, around 1.2 to 1.3 times higher than long (LPeI 77–82), anterior and posterior faces approximately parallel, anterodorsal and posterodorsal margins situated at about the same height, petiolar dorsum clearly convex; node in dorsal view between 1.1 to 1.2 times longer than wide (DPeI 85–92), in dorsal view pronotum around 2.0 to 2.2 times wider than petiolar node (PeNI 46–51). Postpetiole in profile globular to subglobular, approximately 1.3 to 1.4 times higher than long (LPpI 71–77); in dorsal view around 1.3 to 1.4 times wider than long (DPpI 128–138), pronotum between 1.3 to 1.5 times wider than postpetiole (PpNI 67–76). Postpetiole in profile usually appearing less voluminous than petiolar node, postpetiole in dorsal view around 1.4 to 1.5 times wider than petiolar node (PPI 143–149). Mandibles and clypeus usually fully unsculptured, smooth, and shining, mandibles sometimes with few traces of rugulae apically; cephalic dorsum between frontal carinae mostly unsculptured and shiny, median ruga present and distinct, cephalic dorsum also puncticulate to punctate throughout its length, posteriorly close to posterior head margin especially pronounced; scrobal area partly unsculptured, smooth and shiny and partly merging with surrounding rugose sculpture on sides of head. Ground sculpture on head usually weak to absent. Dorsum of mesosoma mostly unsculptured, smooth and shiny with scattered punctures, rarely with few traces of rugulae; lateral mesosoma longitudinally rugose and very conspicuously reticulate-punctate except for mostly unsculptured lateral pronotum and katepisternum. Forecoxae unsculptured, smooth, and shining. Petiolar node and postpetiole superficially longitudinally rugulose or irregularly rugulose superimposed on conspicuous but relatively weak reticulate-punctate ground sculpture. Mesosoma and waist segments appearing mostly matt. First gastral tergite unsculptured, smooth, and shiny. Pilosity and pubescence greatly reduced: head with few pairs of moderately long, standing hairs, anterior pronotum with one long pair, waist segments sometimes with one long pair each, and sometimes first gastral tergite with one long pair; appressed pubescence present everywhere on body, but noticeable only on antennae, cephalic dorsum, legs, and first gastral tergite. Anterior edges of antennal scapes and dorsal (outer) surfaces of hind tibiae with appressed hairs. Body strongly bicoloured with dark brown to black gaster contrasting with light brown to reddish brown remainder.

Type Material

Determination Clarifications

The distribution range of T. decem is far smaller than previously thought. Indeed, most of the material listed in the literature as T. decem or labelled as such in museum collections turned out to be either Tetramorium ultor or Tetramorium venator, while only a few collections proved to be genuine T. decem.

References

References based on Global Ant Biodiversity Informatics

  • Belshaw R., and B. Bolton. 1994. A survey of the leaf litter ant fauna in Ghana, West Africa (Hymenoptera: Formicidae). Journal of Hymenoptera Research 3: 5-16.
  • Belshaw R., and B. Bolton. 1994. A survey of the leaf litter ant fauna in Ghana, West Africa (Hymenoptera: Formicidae). Journal of Hymenoptera Research. 3: 5-16.
  • Bernard F. 1953. La réserve naturelle intégrale du Mt Nimba. XI. Hyménoptères Formicidae. Mémoires de l'Institut Français d'Afrique Noire 19: 165-270.
  • Dejean A., J. L. Durand, and B. Bolton. 1996. Ants inhabiting Cubitermes termitaries in African rain forest. Biotropica 28(4): 701-713.
  • Durou S., J. Lauga, and A. Dejean. 2001. Intensive food searching in humid patches: adaptation of a Myrmicine ant to environmental constraints. Behaviour 138: 251-259.
  • Garcia F.H., Wiesel E. and Fischer G. 2013.The Ants of Kenya (Hymenoptera: Formicidae)—Faunal Overview, First Species Checklist, Bibliography, Accounts for All Genera, and Discussion on Taxonomy and Zoogeography. Journal of East African Natural History, 101(2): 127-222
  • Hita Garcia F., and B. L. Fisher. 2014. The ant genus Tetramorium Mayr in the Afrotropical region (Hymenoptera, Formicidae, Myrmicinae): synonymisation of Decamorium Forel under Tetramorium, and taxonomic revision of the T. decem species group. ZooKeys 411: 67-103.
  • Hita-Garcia F. (Personal communication, 3 July 2015)
  • IZIKO South Africa Museum Collection
  • Kone M., S. Konate, K. Yeo, P. K. Kouassi, K. E. Linsemair. 2010. Diversity and abundance of terrrestrial ants along a gradient of land use intensification in a transitional forest-savannah zone of Cote d'Ivoire. Journal of Applied Biosciences 29: 1809-1827.
  • Kone M., S. Konate, K. Yeo, P. K. Kouassi, and K. E. Linsenmair. 2012. Changes in ant communities along an age gradient of cocoa cultivation in the Oumé region, central Côte d’Ivoire. Entomological Science 15: 324–339.
  • Medler J. T. 1980: Insects of Nigeria - Check list and bibliography. Mem. Amer. Ent. Inst. 30: i-vii, 1-919.
  • Stephens S. S., P. B. Bosu, and M. R. Wager. 2016. Effect of overstory tree species diversity and composition on ground foraging ants (Hymenoptera: Formicidae) in timber plantations in Ghana. International Journal of Biodiversity Science, Ecosystem Services & management 12(1-2): 96-107.
  • Taylor B. 1980. Ants of the Nigerian Forest Zone (Hymenoptera: Formicidae). IV. Myrmicinae (Myrmecinini to Tetramoriini). Cocoa Research Institute of Nigeria Research Bulletin 7: 1-63.
  • Watt, A.D., N.E. Stork and B.Bolton. 2002. The diversity and abundance of ants in relation to forest disturbance and plantation establishment in southern Cameroon. Journal of Applied Ecology 39(1):18-30.
  • Weber N. A. 1952. Studies on African Myrmicinae, I (Hymenoptera, Formicidae). American Museum Novitates 1548: 1-32.
  • Yeo K., S. Konate, S. Tiho, and S. K. Camara. 2011. Impacts of land use types on ant communities in a tropical forest margin (Oumé - Cote d'Ivoire). African Journal of Agricultural Research 6(2): 260-274.
  • Yeo K., T. Delsinne, S. Komate, L. L. Alonso, D. Aidara, and C. Peeters. 2016. Diversity and distribution of ant assemblages above and below ground in a West African forest–savannah mosaic (Lamto, Cote d’Ivoire). Insectes Sociaux DOI 10.1007/s00040-016-0527-6
  • 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.