Lasius pallitarsis

Distribution based on Regional Taxon Lists
Nearctic Region: Alberta, Canada, Canada , United States. Neotropical Region: Mexico.

Biology
Wilson (1955) reported the following biological information under the synonymized name Lasius sitkaensis:

My own studies of sitkaensis in the field, combined with abundant field notes supplied me by A. C. Cole, Kenneth Kraft, G. C. Wheeler, and others, show that this species is primarily a forest dweller, nesting in rotting logs and stumps and under stones. It penetrates forest clearings secondarily and is abundant, at least locally, in the almost treeless plains of central and western North Dakota (P. B. Kannowski, Joe Davis, R. P. Uhlmann; material in G. C. Wheeler ColI. and UMMZ) and southern Idaho (A. C. Cole). In the latter situation it usually nests under stones but occasionally constructs irregular soil craters removed from any ground cover. At Moscow Mountain, Idaho, I found hundreds of nests in rotting wood and under stones within the forest margin, but only one associated with a crater in open soil. In Itasca State Park, Minn., Kraft found six colonies associated with craters, out of sixteen collected. Cole, in collecting Lasius from a wide diversity of habitats in New Mexico, took sitkaensis most consistently under stones in moist, shaded soil. At Cloudcroft, New Mexico, and the San Francisco Peaks, Arizona, I found the species most abundant well back in the shaded portions of the forest, nesting almost exclusively under stones. In the White Mountains of New Hampshire, however, sitkaensis populations are densest nesting under stones in overgrown meadows on the lower slopes, and are less abundant under stones in the adjacent spruce-fir-larch forest.

Local populations of sitkaensis and its relatives Lasius neoniger, Lasius alienus, and Lasius crypticus are often spectacularly dense. It seems inevitable that some amount of interspecific competition must result, and it is therefore not surprising to find a tendency for these species to replace one another ecologically where they occur together. Near Bemidji, in central Minnesota, I found sitkaensis in a deciduous woodlot nesting in rotting logs and stumps, a niche usually occupied by alienus in localities farther east where sitkaensis is rare or absent. neoniqer prevailed in adjacent open areas. At Kiowa, Montana, sitkaensis again seemed to replace alienus in deciduous woods; crypticus was abundant in an adjacent subalpine meadow, while neoniger, its nearest ecological equivalent, was absent. At Moscow Mountain and Cloudcroft, sitkaensis occurred in exceedingly large numbers, apparently to the exclusion of other members of the subgenus.

The food habits of sitkaensis are evidently generalized. Kannowski (in litt.) has found workers on several occasions associated with aphids in galleries under rocks, while at Moscow Mountain I observed workers carrying dead and crippled insects back to their nests during the early part of the night. A colony maintained under observation at the Harvard Biological Laboratories for nearly two years has readily accepted both honey and dead and crippled insects.

Winged forms have been taken in the nests from July 4 (Neche, Pembina Co., N. Dak.; E. L. Krause leg.; G. C. Wheeler Coll.) and July 7 (Cloudcroft, N. Mex., W. M. Wheeler leg.; MCZ) to September 24 (Lodema, Pembina Co., N. Dak.; Krause leg.; G. C. Wheeler Coll.). The great majority of in nido records are from August. G. C. 'Wheeler took pairs flying in copula at Marblehead, Mass., on September 3, 1927, and N. A. Weber took a pair in copula at Towner, McHenry Co., N. Dak., on August 18, 1927 (both G. C. Wheeler Coll.). Eidmann (1933) observed nuptial flights of "americanus" (probably the sitkaensis already referred to) in the Matamek region of Quebec on September 4. Borys Malkin found stray dealate queens at Wrangell, Alaska, in the first week of August.

Castes

 * Worker

Nomenclature

 *  pallitarsis. Formica pallitarsis Provancher, 1881b: 355 (w.m.) CANADA. [Also described as new by Provancher, 1883: 598.] Hung, 1969: 456 (k.). Combination in Lasius: André, 1887: 288. Junior synonym of alienus: André, 1887: 288; Wilson, 1955a: 77. Revived from synonymy and senior synonym of sitkaensis: Francoeur & Béique, 1966: 144. See also: Smith, D.R. 1979: 1437.
 * sitkaensis. Lasius niger subsp. sitkaensis Pergande, 1900: 519 (w.) U.S.A. Wheeler, W.M. 1917a: 525 (q.m.). Junior synonym of neoniger: Creighton, 1950a: 420. Revived from synonymy and raised to species: Wilson, 1955a: 36. Junior synonym of pallitarsis: Francoeur & Béique, 1966: 144.