Lasius minutus

Identification
Wilson (1955) - A distinctive North American species most easily recognized by the small size and unusual pilosity of the queen. (See Lasius bicornis for a more detailed comparison with that species.)

Key to Lasius workers, queens, males

Distribution
Eastern North America.

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



Biology
Notes accompanying specimens records indicate that Lasius minutus prefers to nest in sphagnum bogs and swampy meadows but will also move into open, dry forest. It has been taken most often in mounds or masonry domes in open areas, and only once (Steuben Co., Ind.) in a log. Brown (pers. commun.) has supplied me with complete notes on his Pennsylvania collections. South of Oxford, near the Pennsylvania-Maryland border, he found a population of this species nesting in masonry domes on the open grassy floor of a tongue of pitch pine woods. These domes measured between about 8 and 18 inches in height and about 2 feet in base diameter, had peculiar bulging sides, and were overgrown with short grass. Similar domes were found in a population at Ottsville along the border of an old pasture and oak-hickory woods. At both localities workers were rather scarce in the nests, and at Ottsville some of the domes were inhabited by Formica fusca instead.

A clue to the host species of minutus is supplied by the following note accompanying a series in the United States National Museum: "N. J./Aug. 15 '85/in hickory stem with Lasius alienus." The nesting site is one typical for alienus, and the determination in this case was probably correct. (Wilson 1955)

Nomenclature

 *  minutus. Lasius umbratus subsp. minutus Emery, 1893i: 641 (w.q.m.) U.S.A.
 * Combination in L. (Chthonolasius): Ruzsky, 1914a: 61.
 * Subspecies of umbratus: Wheeler, W.M. 1906b: 13; Wheeler, W.M. 1910e: 241 (redescription); Wheeler, W.M. 1916k: 172.
 * Subspecies of bicornis: Emery, 1925b: 233; Creighton, 1950a: 421.
 * Status as species: Wilson, 1955a: 180 (redescription); Smith, D.R. 1979: 1438; Bolton, 1995b: 224; Coovert, 2005: 126; Ellison, et al. 2012: 194.

Worker
Wilson (1955) - Similar to Lasius umbratus in habitus, but smaller and with distinctive pilosity and petiole shape.

(1) Apparently averaging and ranging smaller than umbratus; extreme PW range 0.52-0.69 mm.

(2) Entire body covered with long, coarse standing hairs, the longest on the alitrunk and gastric tergites at least 0.6 X as long as the maximum width of the hind tibia midpoint and usually much longer. At the same time, the scapes and tibiae completely bare except for a few decumbent hairs along the flexor margins of the tibiae. Pubescence abundant and strongly appressed.

(3) The petiole, measured in frontal view from the level of the dorsal border of the posterior foramen to the level of the dorsolateral corners, longer than its maximum width in frontal view, and usually with a distinctive shape: tapering from the broadest level (just above the foramina) to the dorsal crest and often expanding again just at the level of the crest; the dorsal margin distinctly but shallowly emarginate (Pl. 2, Fig. 4).

(4) The scape rounded in cross-section.

Queen
Wilson (1955) - (1) Smaller than umbratus and Lasius bicornis. HW of all available series ranging 1.02-1.17 mm,

(2) Entire body covered with long, coarse hairs, the longest on the first two gastric tergites longer than the greatest width of the hind tibia at its midlength. Scapes completely bare of standing hairs; tibiae bare except for a few decumbent hairs along the flexor margins of the hind tibiae.

(3) Petiole in frontal view shallowly and angularly emarginate, with very broadly rounded dorsolateral corners.

(4) The scape rounded in cross-section.

Male
(1) Smaller than umbratus and other umbratus complex members. HW range of limited sample measured 0.80-0.92 mm.

(2) Long, coarse standing hairs abundant over body surface, the longest on the clypeus exceeding 0.15 mm., or greater than one-sixth the head width; the longest on the first gastric tergite 0.15 mm., or 1.6 X the maximum width of the hind tibia at its midlength.

Type Material
Wilson (1955) - SYNTYPES. Three nidotopotype workers in the ("N. J./Aug. 25 '85/Pergande") correspond well to syntype workers borrowed from the Emery Collection ("Kittery Point, Me./Aug. '91/no. 285"). I have declined to designate a lectotype because of the good possibility that this former series was not in Emery's hands at the time of original description, but there can be no doubt that the name has been correctly placed.