Lasius flavescens Forel 1904

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 : 66

4.4.32 Lasius flavescens Forel 1904

Lasius niger r. flavescens Forel1904 [typeinvestigation]

Type material: Two type workers labelled ”Sardym, r. Gunt, Shugnan, v. Byx. Kaznak. 16VIII97“ (printed label in Kyrillic), ” L. niger flavescens For type Buchara“, ”ANTWEB CASENT 0911048“, depository: MHN Genève.

All material examined. A total of 17 samples with 45 workers were subject to NUMOBAT investigation. These originated from Afghanistan (2 samples), Kyrgyzstan (10) and Uzbekistan (4). For details see supplementary information SI1.

Geographic range. Known so far only from an area of 200 000 km² covering NE Afghanistan (37°N, 71°E) and the western parts of the Tian Shan mountains north and south of the Ferghana Valley with the westernmost and easternmost points at 39°N, 67°E and 41.6°N, 75.0°E. The altitudinal records vary between 2040 and 3600 m.

Diagnosis (Tab. 5, Figs. 61 –62; key; images in www. AntWeb.org with specimen identifiers CASENT0911048):

Absolute size rather small (CS 844 µm). Head length index rather low (CL/CW 900 1.068); scape short (SL/ CS 900 0.932); postocular distance medium (PoOc/CL 900 0.238); torulo-clypeal distance low (dClAn 900 3.50); eye size medium (EYE/CS 900 0.242); terminal segment of maxillary palp very short (MP6/CS 900 0.161). Number of mandibular dents medium (MaDe 900 8.23). Pubescence on clypeus very sparse (sqPDCL 900 5.18); frontal pubescence long (PLF 900 36.4). All body parts with very numerous standing setae of medium length (PnHL/ CS 900 0.139, GuHL/CS 900 0.115, nGu 900 14.1, nSc 900 23.9, nHT 900 27.9). Coloration: polymorphous but in overall impression always with a strong yellow component. The lighter specimens have the whole body more or less concolorous clear yellow to light yellowish brown. The darker specimens are more bicolored with head and gaster brown with a yellow component and have a lighter yellowish brown mesosoma.

Biology. Tarbinsky (1976), who apparently identified the species correctly, reported L. flavescens to be abundant in Kyrgyzstan, to occur there at elevations of 1600–3200 m in Ferula-Prangos steppes, high-grassy meadows in the fir forest zone and in meadows of the subalpine zone. The nests are populous and frequently found under stones. Tarbinsky called the species a ”typical geobiont“ but accessory epigaeous activity is indicated by eye size which is clearly larger than in subterranean species such as L. austriacus or much larger than in the subterranean subgenera Chthonolasius , Cautolasius or Austrolasius .

Comments. L. flavescens cannot be allocated to a certain species complex. It stands alone as an unmistakable combination of a very hirsute body and appendages, very sparse clypeal pubescence, small torulo-clypeal distance, short terminal segment of maxillary palps, short scape and a strong yellow component in mesosomal color. There is much variation in the material suggesting that more than one species could be involved. Bright yellowish specimens with a longer scape, smaller torulo-clypeal distance and more dilute frontal and genal pubescence were observed in more southwestern parts of the range whereas darker specimens with smaller SL/CS 900, larger dClAn 900 and slightly denser pubescence show a more northwestern distribution. However, samples for which most standard characters have been recorded are too few, only four in the lighter and ten in the darker morph, to reliably run exploratory data analyses and a subjective inspection does also not speak a clear language. The problem has to be re-considered by future investigators after more samples are available.

Figures

Figs. 61 and 62: Lasius flavescens; paratype, CASENT0911048,photo Z. Lieberman