Lasius atopus

This California endemic was first collected from a nest in very dry soil under a stone in an unshaded, very arid semidesert area. There was no evidence of foraging activity during the mid-morning period when the collection was made. The small series was obtained with difficulty, one specimen at a time, by digging into the nest galleries to a depth of about two feet. Nest chambers were not found and the queen was not observed.

Identification
This species is apparently not closely related to any known form of Lasius. In its profuse pilosity it is somewhat reminiscent of Lasius vestitus, but it bears little resemblance otherwise. Its large size, slender body, emarginated head, long appendages, and the small many-faceted eyes, set the ant apart strikingly.

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



Nomenclature

 *  atopus. Lasius (Chthonolasius) atopus Cole, 1958a: 75, fig. 1 (w.) U.S.A.

Type Material


The holotype and a series of 14 paratypes were collected. The holotype and a series of paratypes are in the A.C. Cole collection. Paratypes were to be deposited in the Museum of Comparative Zoology and the U. S. National Museum as well as in the collection of Dr. W. S. Creighton. The MCZC does not hold paratypes.

Description
Head length, measured from mid-anterior border of median clypeal lobe to midpoint of a plane projected across occipital corners, 1.19 min. maximum head width, excluding eyes, 1.07 win.; scape length, 1.48 nim.; maxillary palp length, 0.77 mm.; total length of alitrunk, 1.72 win.; pronotal width, 0.76 mm.; maximum diameter of eye, 0.12 mm.

Head notably longer than broad, widest through the region between the eyes, narrowed perceptibly toward mandibular articulations, posterior corners well rounded, median occipital border rather deeply, broadly, and evenly emarginate; median lobe of clypeus strongly convex, sharply longitudinally carinate mesally, anterior border entire and evenly rounded; eyes small, consisting of more than 35 facets; scapes. very long, in repose passing occipital corners by a distance of greater than one-third their length; mandibles with eight teeth; maxillary palpi very long, extending in repose to a plane passing from anterior margin of eye to gula.

Alitrunk comparatively slender, with a rather deep and very broad impression between mesonotum and propodeum when viewed in profile; propodeum in profile as high as mesonotum, its basal surface short, nearly straight, and meeting the long, broadly convex declivity at a well rounded angle. Legs very long. Petiolar scale spatulate, and anterior face nearly perpendicular, its posterior face with a gradual declivity from apex to base; apical border broadly and evenly convex, entire, rather blunt; viewed in profile, not greatly thicker basally (0.15 mm.)than apically (0.13 mm.).

Entire body, with exception of the eyes, the pronotal collar, and the anterior and posterior surfaces of petiolar scale, densely pilose. Hairs chiefly erect but some suberect, golden, slender, pointed; maximum length on head (where they are longest mainly on vertex, occiput, and clypeus), 0.14 mm.; maximum length on scapes, 0.05 mm.; maximum length on pronotum (where hairs are longer than elsewhere on alitrunk, 0.19 inns.; maximum length on first gastric tergite, 0.19 mm., considerably exceeding four-fifths of maximum width of hind tibia at its midlength.

Entire body surface highly shining and shagreened, except for the longitudinally striate and subopaque mandibles and the subopaque antennae. Pubescence moderately long, fully appressed, and rather dilute on head and alitrunk; long and somewhat more dense on gaster where it at no place conceals the shining integument.

Thorax, legs, and petiolar scale a light tan, the head slightly darker; mandibles reddish brown; gaster a slightly infuscated light tan.

Variation in the paratype series. The following measurements are extremes, the minimal figures applying to the smallest worker. Head length, 1.11-1.22 mm.; head width, 0.90-1.09 nun.; scape length, 1.36-1.48 mm.; pronotal width, 0.65-0.76 mm.; alitrunk length, 1.53-1.72 mm. Greatest length of cephalic hairs, 0.14-0.14 mm.; of pronotal hairs, 0.17-0.19 mm.; of gastric hairs on first tergite, 0.15-0.19 mm. Two of the workers have the posterior margin of the head less strongly emarginated than do the others. Some specimens show a considerable degree of infestation by the fungus, Laboulbenia formicarum Thaxter.