Lasius neglectus Van Loon et al. 1990

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 : 51

4.4.7 Lasius neglectus Van Loon et al. 1990

Lasius neglectus Van Loon, Boomsma & Andrasfalvy 1990 [type investigation]

Type material: 7 paratype workers from the holotype colony labelled ” HUNGARY Budapest 1. VII 1988 “; depositories: BMNH London, SMN Görlitz.

All material examined. A total of 69 nest samples with 207 workers were subject to NUMOBAT investigation. These originated from Belgium (3 samples), Bulgaria (1), Georgia (5), France (6), Great Britain (1), Germany (4), Greece (5), Hungary (1), Iran (1), Israel (1), Italy (1), Kyrgyzstan (6), Poland (1), Romania (2), Spain (5), Turkey (25), Uzbekistan (1). For details see supplementary information SI1.

Geographic range. Highly invasive species having spread from a center most probably situated in Asia Minor. Currently known distribution: Tenerife , Iberia, France, Switzerland, Corsica, Italy, S England, Netherlands, Belgium, Germany, Poland, Hungary, Balkans , Ukraine, Cis- and Transcaucasia, Asia Minor, Iran, Uzbekistan, Kyrgyzstan (75°E), Israel. Invasion of Europe and Middle Asia started in about 1973. The northernmost known site in Europe by the year 2013 is Rostock (54.1°N). There is a clear potency for spreading to S Scandinavia because some Asian populations survive in regions with mean January temperatures of –5° C. In Asia Minor most abundant below 1000 m but some populations also ascend to 1900 m.

Diagnosis ( Tab. 2 , Figs. 13 –14; key; images in www. antWeb.org with specimen identifiers CASENT0173143, CASENT0280447, CASENT0903220):

Body size small (CS 772 µm). Number of mandibular dents low (MaDe 900 7.3). Clypeal pubescence dilute (sqPDCL 900 5.39). Pronotal setae rather short (PnHL/ CS 900 0.127), not much longer than gular setae (GuHL/ CS 900 0.115). Petiole scale in lateral view thin and forming an acute tip. Pubescence hairs on frons rather long (PLF 34.1 µm). Dorsum of scape and hind tibiae without or few, occasional setae. Coloration: Head, mesosoma and gaster dark brown; mandibles, antennae, tibiae and tarsae light yellowish-brown. For separation from L. turcicus and L. precursor sp. nov. see key.

Biology. See the short summary in Seifert (2018).

Comments. This invasive species has been issue of perhaps a hundred publications during the last three decades. The determination in the introduction areas, where no L. turcicus or L. precursor sp. nov. are present, is usually easy because of its impressive colony structure but initial colonies might be confused with L. psammophilus and L. obscuratus . The latter species differ from L. neglectus by longer pronotal setae, shorter maxillary palps and higher number of mandibular dents. The separation from the sister species L. turcicus and L. precursor sp. nov. is most challenging and requires complex character combinations. Using 15 standard characters (MP6/CS 900 excluded) in exploratory data analyses, 55 nest samples of L. neglectus are separated from of 128 nest samples of L. turcicus and L. precursor sp. nov. with the following error rates: 3.8% in NC-Ward, 2.2% in NC-part.kmeans, and 3.3% in NC-NMDSkmeans – in the mean 3.1%. This is below the 4% error threshold accepted here to indicate heterospecificity. Reducing the number of characters to 10 (CS, CL/CW 900, SL/CS 900, nHT 900, nOcc 900, nGU 900, GuHL/CS 900, nSt 900, dClAn/CS 900, EYE/CS 900) the performance is slightly improved: 3.8% in NC-Ward, 1.6% in NC-part.kmeans, and 2.2% in NC-NMDS-kmeans, giving a total mean of 2.5%.

Figures

Figs. 13 and 14: Lasius neglectus; paratype