Lasius excavatus

L. excavatus appears to be arboricolous and is probably an Iranian endemic. The climatic conditions within the highland desert of Iran are harsh due to high aridity, high summer temperatures and very cold winters. This species was found in rare spots with less extreme conditions allowing growth of trees: a light Quercus woodland and a light stand of broad-leafed trees in the ancient settlement of Maymand. (Seifert 2020)

Identification
Palaearctic Lasius s. str. species belonging to the Lasius brunneus species complex.

Distribution
Seifert (2020) - Only known from the two type localities in the highland desert of S Iran at elevations of 2200–2500 m.

Distribution based on Regional Taxon Lists
Palaearctic Region: Iran.

Nomenclature

 * . Lasius excavatus Seifert, 2020: 48, figs. 7-8 (w.) IRAN.

The low number of mandibular dents (MaDe900 7.00), the linear profile lines of the dorsum and posterior slope of propodeum, the sharp dorsal crest of petiole scale, the very smooth pubescence on scapes and tibiae, the strongly reduced pilosity, the short pronotal setae (PnHL/CS900 0.102) and the short frontal pubescence (PLF900 23.2 µm) place Lasius excavatus within the Lasius brunneus species complex. The main difference to the three related species L. brunneus, Lasius silvaticus and Lasius himalayanus are the longer scape (SL/CS900 0.974), the shorter postocular index (PoOc/CL900 0.222) and a suggested excavation of posterior head margin. The coloration is similar to the situation in L. brunneus, yet with two of the six type specimens a little darker.

See table 1 in Seifert 2020 for additional morphometrics. The abbreviated names of various quantitative data shown above are defined here: Seifert 2020 Lasius characters.

Type Material
Holotype plus 2 paratype workers labelled ”IRAN: 30.229°N, 55.375°E, Shar-e-babak: Maymand, on trees in garden, 2220 m, O. Paknia 2004.06.11 -169“; 3 paratype workers labelled ”IRAN: 30.900°N, 51.419°E, Sisakht, Kharidun, 2500 m, oak steppe forest, on tree, O. Paknia 2007.07.10 -1727“; all material stored in.

Etymology
The species name refers to the shape of posterior head margin.