Palaearctic Lasius s. str.

Based on Seifert 2020.

The subgenus Lasius s. str. is characterized by large-eyed workers, elongated maxillary palps and more or less intensive above-ground foraging. Most species appear to be monogynous but there are a few polygynous-polydomous and supercolonial species. The habitats are highly variable, e.g., they are found in arid semideserts, wet quaking Sphagnum stands in peat bogs, paved parking grounds in city centers, and damp, dark, broad-leafed forest with a thick carpet of litter.

Only a relatively small part of the ~ 100 species of Palaearctic Lasius s. str. species can be readily placed into a species complexes based on their external morphology.

Lasius brunneus species complex

Mean number of mandibular dents low (MaDe900 7.0– 7.3). Dorsum and slope of propodeum in lateral view linear and forming a distinct, obtuse angle. Petiole scale in lateral view thin and forming an acute tip; its dorsal crest in anterior view straight, slightly concave or slightly emarginate. Pubescence on scape and tibiae and many other body parts very smooth, appressed. Mean length of pubescence hairs on frons very low (PLF900 23.2–25.1 µm). Setae numbers on all body parts low (nOcc900 + nGu900 + nSt900

Lasius turcicus species complex

Mean number of mandibular dents low (MaDe900 7.3– 7.7). Petiole scale in lateral view thin and forming an acute tip; its dorsal crest in anterior view straight or slightly emarginate. Clypeal pubescence dilute (sqPDCL900 5.1– 5.5). Mean length of pubescence hairs on frons larger (PLF900 30–38 µm). Dorsum of scape without or with only very few setae. Setae numbers on head and mesosoma larger than in the L. brunneus complex (nOcc900 + nGu900 + nSt900 11.8–29). Six species:

Research by Borowiec and Salata (2022), examining the ants of Greece, presented a single description for the members of this complex that occur there (Lasius turcicus, L. neglectus and L. precursor): Moderately large to large ML 0.83-1.16, L. neglectus: HL 0.653-0.929 (mean 0.826), HW 0.559-0.849 (mean 0.743); L. precursor : HL 0.711-0.912 (mean 0.792), HW 0.635-0.853 (mean 0.714); L. turcicus: HL 0.749-1.050 (mean 0.895), HW 0.646-0.989 (mean 0.822). Scape moderately elongate, L. neglectus: SL 0.644-0.861 (mean 0.776), L. precursor: SL 0.667-0.833 (mean 0.735), L. turcicus: SL 0.702-0.949 (mean 0.835). Color. Head and gaster usually reddish brown to pale brown, mesosoma usually yellowish brown, antennae and legs pale yellowish brown. Some colonies pale colored, mostly pale yellowish brown, other dark colored, mostly brown with slightly paler mesosoma, antennae and legs. Specimens from colonies with very small workers often very dark colored, predominantly brown. Structure and setation. Head slightly elongated, with convex sides and straight posterior margin. Terminal segment of maxillary palpi long with length of sixth segment: L. neglectus 0.133-0.164 (mean 0.153), L. precursor 0.130-0.165 (mean 0.149), L. turcicus 0.141-0.186 (mean 0.169). Occipital part of head with 14-24 erected setae. Gena with 4-6 erected setae, underside of head with 4-6 erected setae. Mesosomal dorsum with several short erected setae. Length of the longest seta: L. neglectus 0.090-0.134 (mean 0.112), L. precursor 0.080-0.116 (mean 0.098), L. turcicus 0.099-0.131 (mean 0.109). Below propodeal spiracle 3-5 erected setae. Masticatory border of mandibles with 7 teeth. Antennal scapi with smooth pubescence lacking erected setae or at most with one erected setae. Hind tibiae on external surface in basal parts usually without, occasionally with 1-3 erected setae. Ventral surface of fore femora with 4-7 and mid femora 2-5 erected setae, of hind femora with 1-3 setae close to base of femur, anterior surface of fore coxa with several long erected setae. Pubescence on the whole body and appendages very dense and whitish. Pubescence of clypeus very sparse, not covering Clypeus. Surface of gastral tergites distinctly sculptured , first gastral tergite in central part with numerous erected setae. Propodeum in lateral view rather low and obtuse, metanotal groove shallow.

Lasius obscuratus species complex

Mean number of mandibular dents not reduced (MaDe900 8.1–8.4). Scape and head not elongated (SL/ CS900 0.926–0.962, CL/CW900 1.059–1.087). Dorsum of scape without or with few semierect setae (nSc900 0.4- 0.8). Hind margin of head always with rather many setae (nOcc900 8.2–11.0). Four species:

Lasius paralienus species complex

Mean number of mandibular dents not reduced (MaDe900 8.0–8.5). Pubescence very dense and rather long (sqPDCL900 3.39–3.51, PLF900 31.8–38.9). Scape and head moderately elongated (SL/CS900 0.968–1.007, CL/CW900 1.066–1.076). Dorsum of scape without or with very few semierect setae (nSc900 0.2–1.3). Number of setae on extensor profile of hind tibia low (nHT900 1.8–8.6). Hind margin of head always with rather many setae (nOcc900 8.2–12.4). Four species:

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