Lasius alienus (Foerster 1850)

Seifert, Bernhard, 2020, A taxonomic revision of the Palaearctic members of the subgenus Lasius s. str. (Hymenoptera, Formicidae), Soil Organisms 92 (1), pp. 15-86 : 61

4.4.21 Lasius alienus (Foerster 1850)

Formica aliena Foerster 1850 [type investigation]

Type material: Neotype worker plus 10 workers from the neotype nest labelled “GER: Eifel, 7.9. 1991, 37 km SE Aachen, Schleiden“; depositories SMN Görlitz, BMNH London.

All material examined. A total of 237 nest samples with 706 workers were subject to NUMOBAT investigation. These originated from Andorra (1 sample), Austria (1), Bulgaria (5), China (3), Czechia (9), England (3), France (2), Georgia (2), Germany (133), Greece (9), Iran (5), Kazakhstan (14), Kyrgyzstan (5), Russia (1), Slovakia (7), Spain (6), Sweden (1), Turkey (29), and Ukraine (1). For details see supplementary information S1.

Geographic range. Huge Eurosiberian range, largely temperate to submeridional. From N Iberia and S England east to Bogda Shan Mountains (43.9°N, 88.2°E). Northern border of distribution in Central Europe at 53.3°N. A finding in S Sweden (near Revinge, 57.7°N) seems isolated. The southern border in the W Palaearctic runs along the southern Turkish border to the Iranian Elburz Mountains (36.7°N, 50.3°E). The dependency of altitudinal distribution (ALT, in meters) latitude (LAT, in degrees) for 103 localities follows the rule ALT= – 93.1*LAT + 5172 (r=0.701, p<<0.001). The upper limit is 2400 m at 40.6°N in Asia Minor but it may occur at similarly low latitudes close to sea level given the habitat provides sufficient shade. For details see supplementary information S1.

Diagnosis (Tab. 5, Figs. 41 –42; key; images in www. antWeb.org with specimen identifiers CASENT0179927, FOCOL0751):

Absolute size small (CS 823 µm). Scape length index small, head and maxillary palp length indices medium (SL/ CS 900 0.946, CL/CW 900 1.069, MP6/CS 900 0.181). Number of mandibular dents medium (MaDe 900 8.18). Clypeal pubescence moderately dense, intermediate between the situation in the L. paralienus and L. obscuratus species complexes (sqPDCL 900 4.11). Pronotal setae relatively long (PnHL/CS 900 0.152). Setae number on hind margin of head low (nOcc 900 4.9). Gular setae absent or very few (nGu 900 0.8). Dorsum of scape and extensor profile of hind tibia without or with very few semierect setae (nSc 900 0.1, nHT 900 0.9). The best separation from all other species with reduced scape and tibial pilosity is the strong setae reduction on metapleuron below propodeal spiracle (nSt 900 0.3). Frequent coloration: Head, mesosoma, coxae and gaster medium brown; antenna, tibiae and tarsae light yellowish brown; mandibles light reddish brown.

Biology. See Seifert (2018).

Comments. L. alienus shows a weak morphological variation throughout its range stretching over 6600 km from the east to the west and 1900 km from the south to the north. Attempts to cluster geographic populations by NC-clustering showed error rates clearly above 4%. L. alienus cannot be allocated to a certain species complex based on morphological data and is safely separated from any similar species by different algorithms of NCclustering in combination with an LDA.

Figures

Figs. 41 and 42: Lasius alienus; CASENT0179927, photo E. Prado