Trichomyrmex abyssinicus

No information has been published about the biology of .

Identification
Bolton (1987) - Worker. TL 2-6-6-7, HL 0-68-2-04, HW 0-60-1-94, CI 86-100, SL 0-50-1-06, SI 55-110, PW 0-38-0-90, AL 0-72-1-74 (40 measured).

Workers in any series showing remarkable size variation and exhibiting simple monophasic allometry. Mandibles longitudinally rugose, armed with 3 teeth; sometimes also with a minute offset basal denticle or blunt angle following the basal tooth. In larger workers the 3 teeth sometimes blunted or worn away. Anterior clypeal margin concave medially between a pair of prominent teeth which are situated on the margin in front of the antennal insertions. These teeth tend to be relatively larger, longer and more acute in small workers than in large ones. Eyes set slightly in front of the midlength of the sides, the maximum diameter of the eye 0-14-0-24 x HW; the relative size of the eye decreasing with increased head size.

Relative length of scape decreasing with increased head size, as follows.

When HW < 0-70 then SI is >90;

when HW 0-70-1-00 then SI 88-75;

when HW 1-00-1-30 then SI 75-66;

when HW 1-30-1-60 then SI 66-58;

when HW l-60->l-90 then SI 58-55.

In large workers the head in full-face view with the sides approximately straight and more or less parallel; in small workers the sides of the head diverging anteriorly. With alitrunk in profile the metanotal groove impressed. Propodeal spiracle a vertical or near-vertical ellipse of slit. Petiolar peduncle with a conspicuous anteroventral process which when best developed consists of a triangular lamella followed by a broad flange. This process varies considerably in shape and size between series, and between differently sized members of the same series. At its most reduced the process appears as an elongate flange with a rounded anteroventral angle. Petiolar spiracle at or close to the midlength of the peduncle. Elongate standing hairs sparse on cephalic dorsum in large workers, may be absent in smallest individuals. Entire dorsum of head with short decumbent to appressed pubescence, relatively sparse and directed towards the midline. Dorsal alitrunk with numerous standing hairs in largest workers but these may be absent from the propodeum in small workers. In the very smallest individuals the promesonotum may also lack standing hairs. Petiole, postpetiole and gaster with sparse backward directed hairs and with decumbent to appressed moderately dense pubescence.

Dorsum of head behind the costulate or rugulose clypeal region utterly smooth and featureless between scattered hair-pits. In all workers except the very smallest the area on the side of the head between the eye and the clypeus with longitudinal costulae or rugulae. Promesonotal dorsum longitudinally rugulose or with disorganized rugulae, to smooth. Sometimes with a few widely scattered punctulate patches or faint rugular vestiges. In general larger workers are more strongly sculptured than smaller workers. Propodeal dorsum transversely to obliquely rugulose in large to medium workers, the rugulae becoming weak and irregular with reduced size, almost obliterated in the smallest. In the range from largest to smallest workers punctate sculpture usually becomes more apparent with decreasing size on the propodeal dorsum. Sides of alitrunk sculptured, again the density and intensity diminishing with decreasing size. First gastral tergite unsculptured in all sizes.

Colour varying between series and between individuals of different sizes in the same series. Large to medium workers varying from reddish brown to dark brown with a reddish tint, sometimes with reddish black areas on the head and alitrunk. Gaster darker than head and alitrunk, usually blackish brown to black. Smallest workers much lighter in colour, with the head and alitrunk dull yellowish brown to light brown and the gaster darker in shade.

Sharaf et al. (2016) - Trichomyrmex abyssinicus can be distinguished from other Arabian species except Trichomyrmex perplexus by the vertical ellipse or slit propodeal spiracle. This species is similar to T. perplexus but can be separated from it by the convex promesonotum outline, the distinctly longer propodeal dorsum, and the irregularly rugulose propodeum, petiole and postpetiole.

Distribution
Sharaf et al. (2016) – Arabian Peninsula The distribution of T. abyssinicus appears to be restricted to the southwestern mountains of Saudi Arabia, since several years of collecting efforts by the senior author did not retrieve material from any region in the country except the present record, the first record from Saudi Arabia.

Distribution based on Regional Taxon Lists
Afrotropical Region: Benin, Burkina Faso, Ethiopia, Ghana, Nigeria, Sudan, United Arab Emirates.

Nomenclature

 *  abyssinicus. Holcomyrmex abyssinicus Forel, 1894b: 83 (w.) ETHIOPIA. Viehmeyer, 1923: 91 (q.). Combination in Monomorium: Forel, 1910f: 250; in Trichomyrmex: Ward et al., 2014: 16. See also: Bolton, 1987: 321.

Worker
Sharaf et al. (2016) - Workers of this species exhibit marked size variation in any nest series.

Large workers With a broad size variation (TL 2.60–6.70; HW 0.60–1.94). TL 3.55–5.35; HL 1.06–1.53; HW 1.05–1.56; SL 0.78–0.92; EL 0.14–0.20; ML 1.05–1.56; PW 0.52–0.70; PTL 0.28–0.40; PTW 0.17–0.24; PPL 0.23–0.30; PPW 0.21–0.31; CI 98–105; EI 12–14; SI 59–74 (n = 6). Worker TL 2.60–6.70; HL 0.68–2.04; HW 0.60–1.94; SL 0.50–1.06; PW 0.38–0.90; ML 0.72–1.74; CI 86–100; SI 55–110 (Bolton 1987).

Head. In full-face view with emarginated posterior margin and nearly parallel sides; posterior corners strongly rounded; mandibles blunted; scapes when laid back from their insertions fail to reach posterior margin of head.

Mesosoma. Metanotal groove broad and distinctly impressed in profile; promesonotum strongly convex in profile; propodeal spiracle a vertical ellipse or slit; propodeal dorsum about twice as long as propodeal declivity in profile.

Petiole. Petiolar peduncle with a distinct anteroventral process that consists of a triangular lamella followed by a broad flange; petiolar spiracle situated at midline of petiolar peduncle.

Pilosity. Underside of head with short straight hairs not forming a distinct psammophore; cephalic pilosity sparse; mesosoma with abundant standing hairs, the longest on pronotum and mesonotum, propodeal pilosity shorter; petiole, postpetiole and gaster with abundant, sparse suberect hairs.

Sculpture. Cephalic surface smooth and shining except area in front of eyes, which is finely rugulose in profile; mandibles strongly longitudinally rugulose; promesonotal dorsum strongly longitudinally rugulose or with disorganized rugulae, to smooth; propodeal dorsum distinctly transversely rugulose; mesosomal sides strongly rugulose; petiole and postpetiole irregularly rugulose, gaster smooth and shining.

Colour. Head, mesosoma, petiole and postpetiole reddish brown or dark brown, gaster darker than head and mesosoma, blackish brown or black; head with a dark median longitudinal line in full-face view.

Small workers Measurements. TL 2.43–3.37; HL 0.65–0.89; HW 0.60–0.88; SL 0.57–0.70; EL 0.14–0.16; ML 0.70–0.99; PW 0.33–0.45; PTL 0.21–0.28; PTW 0.11–0.14; PPL 0.14–0.21; PPW 0.16–0.18; CI 90–98; EI 18–24; SI 80–95 (n = 8). With a broad size variation.

Head. In full-face view with emarginated posterior margin and sides diverging anteriorly; anterior clypeal margin distinctly concave medially between two well developed teeth that are situated anteriorly in front of the antennal insertions; mandibles armed with three teeth; eyes small, situated in front of midline of head sides (EL 0.14-0.24 × HW), with eight ommatidia in longest row; antennal scapes distinctly short, when laid back from their insertions they fail to reach posterior margin of head.

Mesosoma. Promesonotum nearly flat in profile; propodeal spiracle a vertical ellipse or slit; propodeal dorsum about twice as long as propodeal declivity in profile.

Petiole. Petiolar peduncle with a distinct anteroventral process that consists of a triangular lamella followed by a broad flange; petiolar spiracle situated at midline of petiolar peduncle.

Pilosity. Subcephalic pilosity short and sparse; cephalic pilosity sparse, short, decumbent to appressed pubescence, and directed inward to midline of head.

Sculpture. Cephalic surface smooth and shining except for area in front of eyes, which is finely rugulose in profile; mandibles strongly longitudinally rugulose; propodeal dorsum weakly, irregularly, transversely rugulose; mesosomal sides faintly rugulose; gaster smooth and shining.

Colour. Lighter than large workers, pale brown or yellowish brown, gaster dark brown.

Type Material
Sharaf et al. (2016) - Ethiopia: Afrotropic. Syntype workers [examined]. (Lectotype here designated: Erythrea, Ghinda, III.06 (Dr. Escherich) (CASENT0249906)).