Lasius magnus

Lasius magnus is relatively large, as is the temporary social parasite Lasius crinitus. Their similarity in size coupled with their co-occurence suggests the former is the host of the latter.

Identification
Seifert (2020) - The unique character combination of L. magnus should exclude confusion with any other species. Small workers can be clearly distinguished from equal-sized specimens of other species by a combination of elongated head, low number of mandibular dents, short pronotal setae, extremely dilute clypeal pubescence and the diagnostic pubescence pattern on gaster tergites. There are three samples in with no setae but only a fine pubescence on the dorsal crest and the sides of petiole scale. In other samples the scale is fringed in frontal view by a number of setae. I assume intraspecific polymorphism but the issue should be checked for taxonomic significance. The exceptionally large size of workers and queens in L. magnus, the exceptionally large size in the temporary social parasite Lasius (Chthonolasius) crinitus, and their syntopic occurrence strongly suggest the former represents the host of the latter.

Distribution
Seifert (2020) - Known from 16 sites at the southern flank of the Himalayas at elevations between 1700 and 3100 m and along a line delimited by 27.9°N, 86.2°E and 27.4°N, 90.5°E. Two sites from the Meghalaya Mountains (25.45°N, 91.76°E, 1800m; 25.50°N, 91.90°E, 1900 m) are isolated from the main population.

Distribution based on Regional Taxon Lists
Oriental Region: Bhutan, India.

Nomenclature

 *  magnus. Lasius (Lasius) magnus Seifert, 1992b: 43, figs. 33-35, 40 (w.q.) BHUTAN.
 * Status as species: Bolton, 1995b: 223.

Worker
Seifert (2020) - Largest species of the subgenus Lasius s.str. (CS 1153 µm). Head length index very large (CL/CW900 1.138, mean CL/CW without RAV 1.076). Scape length indices large (SL/CS900 1.034, mean SL/CS without RAV 0.978). Postocular and torulo-clypeal distances rather large (PoOc/CL900 0.253, dClAn900 4.90); terminal segment of maxillary palp of medium length (MP6/CS900 0.191). Number of mandibular dents very small (MaDe900 7.11). Pubescence on clypeus extremely sparse (sqPDCL900 7.24); frontal pubescence of medium length (PLF900 27.8). Pubescence on all surfaces smooth or rather smooth. Gaster tergites with a diagnostic pubescence pattern deviating from the strictly longitudinal orientation seen in other Lasius species: the paramedian pubescence hairs on posterior dorsum of tergites are directed caudomediad or even mediad. This unique pattern may be affected in case of polluted surfaces. Setae rather short and of medium numbers (PnHL/CS900 0.119, GuHL/CS900 0.080, nOcc900 10.0, nGen900 1.7, nGu900 3.4, nSc900 14.7, nHT900 16.7). Coloration: all body parts rather concolorous, varying from pale yellowish-reddish brown, over medium brown with yellowish tinge to dark brown.

See table 9 in Seifert 2020 for additional morphometrics. The abbreviated names of various quantitative data shown above are defined here: Seifert 2020 Lasius characters.

Type Material
Seifert (2020) - Holotype and 20 paratype workers labelled ”Gogona, 3100 m 10.-12.6“,“Nat.-Hist.Museum Basel – Bhutan Expedition 1972“; depositories: holotype plus 16 paratypes, 4 paratypes.

References based on Global Ant Biodiversity Informatics

 * Seifert B. 1992. A taxonomic revision of the Palaearctic members of the ant subgenus Lasius s.str. (Hymenoptera: Formicidae). Abhandlungen und Berichte des Naturkundemuseums Görlitz 66(5): 1-67.