LASIUS XEROPHILUS ( HYMENOPTERA : FORMICIDAE ) , A NEW ANT SPECIES FROM WHITE SANDS NATIONAL MONUMENT , NEW MEXICO BY

We describe a new species of the ant genus Lasius collected from the arid Chihuahuan Desert, a very unusual habitat for the genus. The workers, females and males of this species are similar to those of L. neoniger, but have more abundant erect hairs on the

tibia has over 13 (up to 14, usually less than 10 in L. neoniger) and the same surface of the posterior tibia ( Fig. 6) has more than 15 (less than 15 in L. pallitarsis). Female: The females are much more hairy than those of L. neoniger, with more than 20 hairs on the extensor surface of the mid tibia and hind tibia (less than 6 on these surfaces in L. neoniger, based on 6 females from Quebec and Mora Co. NM). Males: Males are easily distinguished from those of L. neoniger as the extensor surface of the mid tibia has more than 5 erect hairs (one or none in two L. neoniger males from Quebec), the same surface of the hind tibia has more than 10 erect hairs (0-2 in L. neoniger).
Mandibles with 5 large, well defined acute teeth (Fig. 4), widely spaced with two denticles (intercalaries) between preapical (second), median (third) and first basal (fourth), apical tooth about twice size of preapical tooth, which is equal in size to remainder (Fig. 4); anterior border of clypeus broadly rounded, surface of clypeus convex, bulging; frontal area poorly defined; sides of head broadly convex, eyes reaching lateral margins, located about 1 112 diameters from base of mandible; vertex slightly concave; scapes extending past occipital borders by about 2 funicular segments; maxillary palps long, extending nearly to foramen magnum; pronoturn broadly rounded; surface joining mesonotum at same level, promesonotal suture well marked (lateral view); propodeum rectangular shaped, somewhat narrowed dorsally, well differentiated from mesonotum, dorsal face short (0.12 mm), posterior face long (0.4 mm); petiolar node concave apically (Fig. 1) Mandible similar to that of worker, except teeth between second, third and fourth teeth larger, about half size of others; eyes large, about 1.5 diameters from base of mandibles; 3 well developed ocelli; vertex straight; scape extends past occipital corner by length of first funicular segment; petiolar node strongly bilobed (Fig. 3) (Fig. 7) without teeth except single angle at apex, rarely a second poorly defined tooth may be present (seen in one specimen); masticatory border broadly convex; median anterior border of clypeus broadly convex, surface convex; head wider posteriorly than anteriorly; eyes large, convex, about 112 diameter from base of mandible; 3 ocelli well developed; scape about as long as first 5 funicular segments; maxillary palps short, reaching about 113 distance to foramen magnum; petiolar node broadly concave (Fig. 2); parameres thickened, apex covered with erect hairs; aedeagus with well developed convex blade, without teeth (Fig. 9); volsella broad with digitus poorly developed. Erect, bristly hairs on all surfaces, but not as abundant as in worker and female. Punctate throughout, except for smooth surface of posterior face of propodeum. Dark brown, scapes, legs and genitalia lighter brown.
Type Series. Holotype worker, 6 paratype workers, 1 paratype female and 6 paratype males in the U.S. National Museum, 54 paratype workers, 4 paratype females and 35 paratype males deposited in the Harvard Museum of Comparative Zoology, Los Angeles County Museum of Natural History, the American Museum of Natural History, the New Mexico Museum of Natural History, the British Museum of Natural History and in the Laboratory for Environmental Biology, University of Texas.
Discussion. This species was recorded from White Sands National Monument and was considered by Wilson (1955) to be L. neoniger, although it differed in being "exceptionally hairy and lighter in color" than typical L. neoniger workers. Wilson concluded that both of these characters may represent adaptations to the extreme environment at the site. This new species is a member of the neoniger species complex, which also includes L. neoniger, L. crypticus and L. sitiens (Wilson 1955). The distributions of sev-era1 related species (L. niger, L. neonigeq L. alienus, L. sitiens, and L. crypticus) are near to or overlap the distribution of this new species. Thus a comparison with these species is necessary to reduce the possibility of misidentifications. The workers, females and males can be distinguished by the abundant erect hairs from most others, except L. pallitarsis, from which the workers and females differ by not having the offset basal mandibular tooth. The workers of L. niger are also hairy, but can be distinguished as they are darker brown than the light yellowish brown L. xerophilus workers. In addition, the penultimate and terminal basal teeth are subequal in size in L. niger. The new species can be distinguished from L. neoniger by the abundant hair on the tibiae, especially the fore tibia (Fig. 10). The workers of L. alienus, L. crypticus and L. sitiens usually lack erect hairs on the scapes and tibiae, which easily separates these species from the new species. Lasius crypticus also inhabits dry, exposed situations and thrives in short-grass prairie semidesert transition (Wilson, 1955).
The males are similar to others in the niger species complex, differing primarily in the abundant erect hairs on the mid and hind tibiae. Males of L. alienus, L. crypticus and L. sitiens have few or no erect hairs on the scapes, which easily separates them from those of L. xerophilus.
Etymology. From Greek, xeros meaning dry and philia referring to love or fondness for dry habitats.
Biology. All specimens of this new species from White Sands National Monument were collected in the extensive sand dunes (gypsum). Small inconspicuous nests were found in interdune areas. Foraging was nocturnal and crepuscular, except on cool days, when activity continued throughout the day. Nests apparently contained about 100 workers. They appeared in habitus in the field to be a species of Conomyrma, although they are much slower and not very excitable. Workers were timid and attempted to hide when nests were excavated. Sexuals were found in nests in July. Flights occurred at 20:OO-23:OO on July 24, 1992 at the Visitor's Center. We would like to thank the personnel of White Sands National Monument, especially Mr. John Mangimeli, for very pleasant company during our trips to White Sands National Monument and allowing us to "camp out" in the Monument library on rainy nights. Mr. William Fuchs made arrangements for our research on the site. Mr. Dennis Ditmanson, superintendent, arranged for permission to conduct the research in the area. Two anonymous