Palaearctic Lasius s. str.

Based on: [[Media:Seifert, B. 2020. A taxonomic revision of the Palaearctic members of the subgenus Lasius.pdf|Seifert, B. 2020. A taxonomic revision of the Palaearctic members of the subgenus Lasius s.str. (Hymenoptera, Formicidae). Soil Organisms 92(1): 15-86]].

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 brunneus
 * Lasius lasioides
 * Lasius himalayanus
 * Lasius silvaticus
 * Lasius excavatus

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:
 * Lasius turcicus
 * Lasius neglectus
 * Lasius austriacus
 * Lasius tapinomoides
 * Lasius precursor
 * Lasius israelicus

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 obscuratus
 * Lasius piliferus
 * Lasius psammophilus
 * Lasius creticus

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:
 * Lasius paralienus
 * Lasius casevitzi
 * Lasius bombycina
 * Lasius kritikos