Technomyrmex horni

A forest species that has been collected from litter samples.

Identification
Bolton (2007) - A member of the Technomyrmex bicolor group. It is certain that more than one real species is concealed within this compound description, which effectively covers all lightly coloured samples of the Technomyrmex bicolor group of the southern Oriental and Malesian regions, under the single name of horni. Material is so sparse, samples are so small and variation within even the small samples is so obvious that more detailed resolution has proved impossible at this time.

There is variation in SI, with some evidence that it increases as HW decreases within single series, and that CI increases as HW increases. Also, the shape of the head seems to become more cordate with increased size. The shape of the clypeal notch is variable. It is frequently quite long and broadly U-shaped but it is shallower and broader in some. Density and intensity of clypeal sculpture varies considerably, as does distance of the metathoracic spiracles from the metanotal groove. The propodeal dorsum may be flat to shallowly convex, with variation within single short series, and the length of the propodeal dorsum also varies. In syntypes of horni it is much longer than the depth of the declivity to the spiracle but variants with the two about equal, to some with the dorsum shorter than the declivity depth to the spiracle, are also encountered. The junction of propodeal dorsum and declivity varies from angular to rounded. Colour variation is as noted above.

Of course, it is possible that all this variation is contained within a single plastic species, but I strongly suspect that further resolution will be possible when more material and lengthier series are available. For the present the following notes on the two already-named forms in this complex are included here.

T. horni syntype workers: Measurements: TL 3.4 - 3.9, HL 0.88 - 0.98, HW 0.80 - 0.95, SL 0.95 - 1.02, PW 0.52 - 0.59, WL 1.18 - 1.30 (4 measured). Indices: CI 90 - 97, SI 107 - 119, OI 23 - 25, EPI 65 - 73, DTI 150 - 159. With the general characters noted above. Median clypeal notch deeper than semicircular. Clypeus immediately posterior to notch punctulate. Metathoracic spiracle far in front of metanotal groove (about 3 spiracle diameters). Length of propodeal dorsum in profile about twice the depth of the declivity to the spiracle, the dorsum flat to shallowly convex; junction of dorsum and declivity angular. Head, mesosoma and petiole brownish yellow, gaster somewhat darker brown. Middle and hind femora and tibiae the same colour as the mesosoma; middle and hind coxae lighter. Middle and hind tarsi yellow, much lighter than femora and tibiae.

T. schimmeri syntype workers: Measurements: TL 2.9 - 3.2, HL 0.70 - 0.74, HW 0.62 - 0.66, SL 0.74 - 0.76, PW 0.41 - 0.42, WL 0.96 - 1.03 (4 measured). Indices: CI 86 - 89, SI 115 - 120, OI 27 - 29, EPI 70 - 79, DTI 152 - 161. With the general characters noted above. Median clypeal notch broad and shallow. Metathoracic spiracle closer than 3 spiracle diameters from metanotal groove. Length of propodeal dorsum in profile about equal to or slightly greater than the depth of the declivity to the spiracle, the dorsum flat; junction of dorsum and declivity angular. Head, mesosoma and petiole yellow to dirty yellow, gaster usually slightly darker in shade. Either all leg segments dull yellow, the same colour as the mesosoma, or the middle and hind coxae alone slightly lighter.

Yamane et al. (2018) Taiwan - Almost entire body very finely and densely punctate and mat; mandible, mesoscutellum and gaster more shiny; petiole nearly impunctate and shiny. Pilosity and coloration almost the same as in the worker. Bolton (2007) noted that in Technomyrmex horni, with the propodeum in profile the dorsum is flat to shallowly convex, but did not mention the weak impression just in front of the angle between the dorsum and declivity. This impression is very often seen in specimens. Specimens from higher elevations are darker in body colour than in those from lower elevations in both workers and queens. The variation in body proportion in workers is much more pronounced in this species than in the related Taiwanese species, Technomyrmex formosensis (see CI and SI for both species). In the measurements the two queens (originated from different colonies) are almost identical except in the values for the pronotal width and mesonotal width; this may be because in the dealate queen the thorax shrinks after shedding the wings. The cell dc1 of the forewing is present in Technomyrmex horni, but absent in Technomyrmex brunneus as the vein 1m-cu is absent.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Krakatau Islands, Malaysia, Singapore. Oriental Region: Cambodia, India, Sri Lanka, Taiwan, Thailand. Palaearctic Region: China.

Nomenclature

 *  horni. Technomyrmex horni Forel, 1912a: 71 (w.q.) TAIWAN. See also: Bolton, 2007a: 84.

Worker
Bolton (2007) - TL 2.9 - 4.3, HL 0.70 - 1.06, HW 0.61 - 0.95, SL 0.74 - 1.20, PW 0.41-0.61, WL 0.90 -1.46 (26 measured). Indices: CI 82 - 97, SI 107 - 134, OI 23 - 30, EPI 65 - 80 DTI 130 - 160.

Head behind clypeus, dorsum of mesosoma, declivity of propodeum and first gastral tergite all entirely lack setae. Gastral tergites 2 - 4 with long stout setae present: second gastral tergite with 2 - 3 pairs, third and fourth tergites each with 3 - 4 pairs. Anterior clypeal margin with a distinct median notch that is semicircular to V-shaped, the margins of the notch meet the lateral portions of the anterior margin through rounded curves, not sharp angles. Posterior margin of head concave, more deeply 50 in larger workers; sides of head convex and convergent anteriorly. With head in full-face view the outer margins of the eyes fail to touch the outline of the sides of the head. Scape index 107 - 134. Clypeal sculpture fine to reticulate-punctulate between posterior margin of notch and clypeal suture. Mesosoma with DTI 130 - 160. In profile the straight-line length of the propodeal dorsum variable but without a conspicuous notch or indentation at its midlength. In profile the head, mesosoma, petiole and gaster yellow to light brownish yellow; usually the head and gaster slightly infuscated with respect to the mesosoma but sometimes the colour uniform. Anterior coxa yellow to light yellowish brown, the same colour as the mesosoma or slightly lighter. Middle and hind coxae off-white to yellow, the same colour as the mesosoma or slightly lighter. All trochanters off-white to yellow. Middle and hind femora and tibiae yellow to very light brown. Tarsi yellow, the same colour as the femora and tibiae or lighter. Sometimes all leg segments are uniformly coloured, the same shade as the mesosoma.

Queen
Yamane et al. (2018) - (n=2; 1 dealate and 1 alate queen). TL 4.5, 5.2; HW 0.97, 0.96; HL 1.01, 0.99; SL 1.00, 1.00; EW 0.25, 0.25; EL 0.32, 0.32; PrW 0.69, 1.04; MsW 0.82, 0.96; CI 96, 97; SI 103, 103.

Head short, only slightly longer than broad, with weakly convex sides and very shallowly emarginate posterior margin. Clypeus anteriorly with broad, moderately deep median concavity; lateral lobes large with round anterior margins; clypeus posteriorly margined by suture. Eye large, almost reaching lateral outline of head or weakly breaking the latter. Distance between posterior ocelli much longer than that between posterior ocellus and anterior ocellus. Scape surpassing posterior margin of head by its 2/5 length. With mesosoma in profile, mesoscutum large composed of anterior slope and posterior flat portion; seen from above, mesoscutellum round, slightly broader than long; mesopleuron divided into two parts by a distinct suture; anepisternum distinctly margined with carina. Metanotum very short (just a narrow band); metapleuron not demarcated from propodeal side by suture. Propodeum with short dorsum and flat declivity, with pair of low tubercles between dorsum and declivity; straight-line length of propodeal dorsum shorter than length of declivity to spiracle; propodeal spiracle located on side of propodeum, very close to its posterior margin.

Type Material
Bolton (2007) - Syntype workers and queen, Taiwan: Pilam (H. Sauter) [examined].

References based on Global Ant Biodiversity Informatics

 * Abe T., S. Yamane, and K. Onoyama. Ants collected on the Krakatau Islands 100 years after the great eruptions. Biogeography 14: 65-75.
 * Alcantara M. J., S. Modi, T. C. Ling, J. Monkai, H. Xu, S. Huang, and A. Nakamura. 2019. Differences in geographic distribution of ant species (Hymenoptera: Formicidae) between forests and rubber plantations: a case study in Xishuangbanna, China, and a global meta-analysis. Myrmecological News 29: 135-145.
 * Asfiya W., R. Ubaidillah, and Sk. Yamane. 2008. Ants (Hymenoptera: Formicidae) of the Krakataus, and Sebesi and Sebuku islands. Treubia 36: 1-9.
 * Bolton B. 2007. Taxonomy of the dolichoderine ant genus Technomyrmex Mayr (Hymenoptera: Formicidae) based on the worker caste. Contributions of the American Entomological Institute 35(1): 1-150.
 * Bolton, B. "Taxonomy of the dolichoderine ant genus Technomyrmex Mayr (Hymenoptera: Formicidae) based on the worker caste." Contributions of the American Entomological Institute 35, no. 1 (2007): 1-149.
 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Chen Y. Q., Q. Li, Y. L. Chen, Z. X. Lu, X. Y. Zhou. 2011. Ant diversity and bio-indicators in land management of lac insect agroecosystem in Southwestern China. Biodivers. Conserv. 20: 3017-3038.
 * Chen Y., C.-W. Luo, H. W Li, Z. H. Xu, Y. J. Liu, and S. J. Zhao. 2011. The investigation of soil ant resources on the West slope of Mt Ailao. Hubei Agricultural Sciences 50(7): 1356-1359.
 * Dad J. M., S. A. Akbar, H. Bharti, and A. A. Wachkoo. 2019. Community structure and ant species diversity across select sites ofWestern Ghats, India. Acta Ecologica Sinica 39: 219–228.
 * Forel A. 1912. H. Sauter's Formosa-Ausbeute. Formicidae (Hym.) (Schluss). Entomol. Mitt. 1: 45-61.
 * Guénard B., and R. R. Dunn. 2012. A checklist of the ants of China. Zootaxa 3558: 1-77.
 * Helms J. A., S. M. Helms, N. I. Fawzi, Tarjudin, F. Xaverius. 2017. Ant community of an Acacia mangium forest in Indonesian Borneo. Serangga 22(1): 147-159.
 * Herwina H., N. Nasir, Jumjunidang, and Yaherwandi. 2013. The composition of ant species on banana plants with Banana Bunchy-top Virus (BBTV) symptoms in West Sumatra, Indonesia. Asian Myrmecology 5: 151-161.
 * Hu C.-H. 2006. Indigenized conservation and biodiversity maintenance on Orchid Island. PhD Thesis, graduate school of the University of Minnesota. 150 pages.
 * Huong N. T. T., P. V. Sang, and B. T. Viet. 2015. A preliminary study on diversity of ants (Hymenoptera: Formicidae) at Hon Ba Nature Reserve. Environmental Scientific Conference 7: 614-620.
 * Li Q., B. D. Hoffmann, Z. X. Lu, and Y. Q. Chen. 2017. Ants show that the conservation potential of afforestation efforts in Chinese valley-type savanna is dependent upon the afforestation method. Journal of Insect Conservation DOI 10.1007/s10841-017-0005-0
 * Li Q., Z. Lu, Z. Wei, M. Yanyan, and F. Ping. 2015. Communities of ground-dwelling ants in different plantation forest in arid-hot valleys of Jinsha river, Yunnan Province, China. Scientia Silvae Sinicae 51(8): 134-142.
 * Li Qiao, Chen You-qing, Guo Xiao, Duan Yan, Chen Yan-lin, and Xu Zheng-hui. 2007. Diversity of ants in differents habitats in Yuanmou arid-hot valley, Yunnan. Journal of Fujian College of Forestry 27(3): 272-277.
 * Li X., D. Hao, and Y. Huang. 2011. Ant species diversity at piedmont of Zijin Mountain in Nanjing. Journal of Nanjing Forestry University ( Natural Science Edition) 35(5): 55-58.
 * Li Z.h. 2006. List of Chinese Insects. Volume 4. Sun Yat-sen University Press
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58
 * Shattuck S. O. 1994. Taxonomic catalog of the ant subfamilies Aneuretinae and Dolichoderinae (Hymenoptera: Formicidae). University of California Publications in Entomology 112: i-xix, 1-241.
 * Song Y., Z. Xu, C. Li, N. Zhang, L. Zhang, H. Jiang, and F. Mo. 2013. An Analysis on the Ant Fauna of the Nangun river Nature Reserve in Yunnan, China. Forest Research 26(6): 773-780.
 * Terayama M. 2009. A synopsis of the family Formicidae of Taiwan (Insecta: Hymenoptera). Research Bulletin of Kanto Gakuen University. Liberal Arts 17:81-266.
 * Terayama, M. 2009. A synopsis of the family Formicidae of Taiwan (Insecta; Hymenoptera). The Research Bulletin of Kanto Gakuen University 17: 81-266.
 * Wheeler W. M. 1928. Ants collected by Professor F. Silvestri in China. Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d'Agricoltura. Portici 22: 3-38.
 * Wheeler W. M. 1929. Ants collected by Professor F. Silvestri in Formosa, the Malay Peninsula and the Philippines. Bollettino del Laboratorio di Zoologia Generale e Agraria della Reale Scuola Superiore d'Agricoltura. Portici 24: 27-64.
 * Wheeler W. M. 1930. A list of the known Chinese ants. Peking Natural History Bulletin 5: 53-81.
 * Xu Z. H., B. L. Yang, and G. Hu. 1999. Formicidae ant communities in fragments of montane rain forest in Xishuangbanna, China. Zoological Research 20(4): 288-293.
 * Yamane S. 2013. A Review of the ant fauna of the Krakatau Islands, Indonesia. Bull. Kitakyushu Mus. Nat. Hist. Hum. Hist. Ser: A, 11: 1-66
 * Zhang Xiang, and Hou You-Ming. 2009. Five new record genus and thirty one new records species of ants (Hymenoptera; Formicidae) in Fujian Province. Journal of Fujian Agriculture and Forestry University 38(5): 479-484.
 * Zryanin V. A. 2011. An eco-faunistic review of ants (Hymenoptera: Formicidae). In: Structure and functions of soil communities of a monsoon tropical forest (Cat Tien National Park, southern Vietnam) / A.V. Tiunov (Editor). – M.: KMK Scientific Press. 2011. 277 р.101-124.