Lasius sakagamii

Widespread in Japan. Occurs in open areas with sandy and alluvial soils, from sea level to 500m.

Identification
Japanese Ant Image Database - Total length of workers around 2.5 - 3.5 mm. Color brown. Scapes as long as the head is wide, and with more than 30 erect hairs. Anterior tibiae with many erect hairs. Petiole thick and low, anterior margin with a weak, blunt angle in lateral view.

Seifert (2020) - Lasius sakagamii represents an unmistakable combination of extremely large setae numbers, flat propodeal dome, low petiole and low clypeal pubescence distance.

Distribution
Widely spread all over Japan from sea level to 500 m. Okinawa records (Naha City) may be an introduced population resulting from human commerce.

Distribution based on Regional Taxon Lists
Palaearctic Region: Japan.

Habitat
Yamauchi, Kinomura, Miyake (1981, part I) - Apparently stenotopic, living mainly in sandy areas with sparse vegetation. Lasius sakagamii particularly prefers flood plains.

Biology
Japanese Ant Image Database - This species nests in the soil in dry environments such as grasslands at riversides or seashores. Nests are polygynous and polydomous, and multiply by budding. The number of contained individuals is large, sometimes reaching several hundred thousand (Yamauchi, 1981; Yamauchi et al., 1981, 1982). The nuptial-flight period is relatively long for a species of subgenus Lasius with records from June to October. Collections of L. sakagamii from Okinawa (Naha City) probably represent an introduction by human commerce. Diploid males are known to occur in this species (found in 20% of 30 examined nests) (Yamauchi et al., 2001).

Seifert (2020) - Main habitat are sun-exposed deposition areas of alluvial and aeolian sands with only sparse vegetation; these are river banks, dry river beds, sand dunes or road sides. Nests are usually constructed at spots with bare sand or under stones and have numerous distinct chambers usually reaching down to 60 cm. Nuptial flights were observed from early July to late September at warm evenings with air temperatures > 22°, high air humidity and no air movements. The species is polygynous and in many nests only males fly. Nuptial flight of gynes only takes place from nests without males, otherwise they mate intranidally with subsequent dispersal flight. It may form supercolonies dominating large habitat areas.

Nomenclature

 *  sakagamii. Lasius sakagamii Yamauchi & Hayashida, 1970: 504, figs. 3, 4, 6, 9, 10 (w.q.m.) JAPAN. See also: Yamauchi, 1979: 157; Seifert, 1992b: 42.

Worker
Seifert (2020) - Medium-sized (CS 887 µm). Head moderately long (CL/CW900 1.071). Scape long (SL/CS900 1.034). Postocular distance small and eye medium-sized (PoOc/ CL900 0.225, EYE/CS900 0.244). Torulo-clypeal distance large (dClAn900 5.21). Number of mandibular dents large (MaDe 8.52). Terminal segment of maxillary palp rather long (MP6/CS900 0.194). Pubescence on clypeus dense (sqPDCL900 3.78) and on frons rather long (PLF900 33.0). Gular and pronotal setae rather long (GuHL/CS900 0.110, PnHL/CS900 0.157). Whole body covered by extremely numerous standing setae (nOcc900 23.4, nGen900 16.1, nGu900 18.6, nSc900 32.0, nHT900 29.8, nSt900 12.6). Mesosoma with very flat propodeal dome and convex to angulate-convex posterior propodeal slope that is transversally carinulate. Petiole scale in lateral view thick, low and with a blunt apex; in anterior view rather narrow, with convex to nearly straight subparallel sides. Coloration: mesosoma medium brown with a yellowish-reddish tinge, head a little and gaster distinctly darker; sometimes whole body concolorous pale or dark brown.

Also see table 11 in Seifert 2020 for additional morphometric measurements, ratios, and functions. Abbreviations given above for measurements, ratios and functions are defined here: Seifert 2020 Lasius characters.

Type Material
Seifert (2020) - One paratype worker from the holotype nest series labelled ”Sapporo Hokkaido 30-VII-1966 K. Yamauchi“; depository.

Karyotype


The diploid chromosome number in female Lasius sakagamii is 30, while the haploid number in normal males is 15. Six of the 30 studied colonies (20%), however, contained many diploid males. Although the body size of the diploid males was, on average, larger than that of the haploid males, both types of males showed normal external and internal morphologies. Furthermore, there was no reduction in chromosome numbers in either diploid or haploid males during spermatogenesis. The spermatid nuclei of diploid males, however, were significantly larger than those of haploid males, and the amount of DNA in the diploid males, as measured by flow cytometry, was twice as much as that in the haploid males, clearly indicating that diploid males produce diploid sperm (Yamauchi et al., 2001).

References based on Global Ant Biodiversity Informatics

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