Technomyrmex horni

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Technomyrmex horni
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dolichoderinae
Genus: Technomyrmex
Species: T. horni
Binomial name
Technomyrmex horni
Forel, 1912

Technomyrmex horni casent0249786 p 1 high.jpg

Technomyrmex horni casent0249786 d 1 high.jpg

Specimen Labels

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.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Borneo, Indonesia, Krakatau Islands, Malaysia.
Oriental Region: Cambodia, India, Sri Lanka, Taiwan (type locality), Thailand.
Palaearctic Region: China.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Castes

Worker

Queen

Male

Nomenclature

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

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

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

Description

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) (Musee d'Histoire Naturelle Genève) [examined].

References

References based on Global Ant Biodiversity Informatics

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