William P. MacKay and Emma E. MacKay.
Lasius xerophilus (Hymenoptera: Formicidae), a new ant species from White Sands National Monument, New Mexico.
Psyche 101(1-2):37-43, 1994.

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LASIUS XEROPHILUS (HYMENOPTERA: FORMICIDAE), A NEW ANT SPECIES FROM WHITE SANDS NATIONAL MONUMENT, NEW MEXICO
BY WILLIAM P. MACKAY AND EMMA E. MACKAY
Laboratory for Environmental Biology
Department of Biological Sciences
The University of Texas
El Paso, TX 79968
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 tibiae.
Lasius is one of the most prominent and familiar of the Holarc- tic ant genera (Wilson 1955). It generally occurs at high elevations or high latitudes in forests and grasslands. We describe a species which occurs in the arid Chihuahuan Desert of south central New Mexico, a habitat which is very unusual for the genus. The genus Lasius commonly occurs in mesic sandy habitats, including sand dunes (Boomsma and De Vries 1980; Gall6 and Szonyi 1988; Gall6 1990, 1991).
Lasius xerophilus new species
(Figures 1-7, 9)
Diagnosis. This species is similar to L. neoniger, and would key to this species in Wilson (1955). Worker: The worker is covered with short, bristly hairs. The extensor surface of the front tibia (Fig. 5) has at least 6, usually over 10 such hairs (as many as 3, usually one or none in L. neoniger), the same surface of the mid Manuscript received 6 April 1993.




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Figs. 1-7 and 9: Lasius xerophilus, Fig. 8: Lasius pallitarsis. 1. Posterior view of petiole of paratype L. xerophilus worker. 2. Similar view of petiole of L. xerophilus male paratype. 3. Similar view of petiole of paratype female L. xerophilus. 4. Left mandible of L. xerophilus paratype worker, b = basal, m = median, p = preapical and a = apical. 5. Anterior view of front tibia of paratype L. xerophilus worker. 6. Similar view of posterior tibia of L. xerophilus paratype worker. 7. Right mandible of paratype male L. xerophilus. 8. Left mandible of Lasius pallitarsis male (NM, Los Alamos Co., 8 KN Los Alamos). 9. Right aedeagus (outer surface) of male paratype L. xerophilus.
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 Que- bec), the same surface of the hind tibia has more than 10 erect hairs (0-2 in L. neoniger).




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Description. Worker measurements (mm): HL (head length) 0.84-0.86, HW (maximum head width) 0.80-0.83, SL (scape length) 0.75-0.79, EL (eye length) 0.20-0.21, WL (Weber's length) 0.93-0.98, CI (cephalic index, HWIHL X 100) 95-97, SI (scape index SLIHL X 100) 87-94.
Mandibles with 5 large, well defined acute teeth (Fig. 4), widely spaced with two denticles (intercalaries) between preapical (sec- ond), 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; prono- turn broadly rounded; surface joining mesonotum at same level, promesonotal suture well marked (lateral view); propodeum rec- tangular 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). Erect, coarse, bristly hairs (0.05-0.1 mm long) abundant on all surfaces (Figs. 5 & 6), golden, decumbent pubescence abundant on head, dorsum of mesosoma and gaster. Light brown, gaster darker brown. Mandibles finely striate, dorsum of head and most of mesosoma and gaster finely punctate. Posterior face of propodeum smooth and shining.
Female measurements: HL 1.46-1.48, HW 1.64-1.65, SL 1.19-1.23, EL 0.38-0.40, WL 3.18-3.26, CI 111-113, SI 81-83. Mandible similar to that of worker, except teeth between sec- ond, third and fourth teeth larger, about half size of others; eyes large, about 1.5 diameters from base of mandibles; 3 well devel- oped ocelli; vertex straight; scape extends past occipital corner by length of first funicular segment; petiolar node strongly bilobed (Fig. 3). Sculpture, hair and pubescence as in worker. Head and dorsum of mesosoma dark brown, side of mesosoma and gaster lighter brown.
Male measurements: HL 0.65-0.69, HW (posterior to eye) 0.68-0.74, SL 0.49-0.51, EL 0.29-0.30, WL 1.43-1.51, CI 99-113, SI 71-78.




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Mandible (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 pos- teriorly 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 con- cave (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. Punc- tate throughout, except for smooth surface of posterior face of pro- podeum. Dark brown, scapes, legs and genitalia lighter brown. Distribution. United States: New Mexico, Otero Co., White Sands National Monument. Specifically, this species occurs in interdunal areas at the Visitor's Center, around the trail head to the back country campground and at the Heart of the Dunes; NM, Bernalillo Co., northwest Albuquerque, 17-iii-1993, Dick Fager- lund (4 workers, 1 in MacKay collection, 3 in Fagerlund collec- tion); NM, Bernalillo Co., Bosque Forest, 6-iv-1990, 20-iv-1990, 7-ix-1990, Cliff Crawford (4 workers, 1 in MacKay collection, 3 in University of New Mexico collection). 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 Labora- tory 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 con- cluded 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-



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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 eas- ily 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.
Material examined. Eighty-nine workers, 5 females and 48 males.
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.



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Fig. 10. A three dimensional plot of the numbers of hairs on the tibiae of two species of Lasius. L. xerophilus, all paratypes from White Sands National Monu- ment, is represented by X's, L. neoniger by the other letters which indicate states and localities where the specimens were collected: A = Minnesota, C = California, I = Illinois, L = Lincoln Co., southern New Mexico, M = Michigan, N = New York, 0 = Mora Co., northern New Mexico and Q = Quebec. We would like to thank the personnel of White Sands National Monument, especially Mr. John Mangimeli, for very pleasant com- pany 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 per- mission to conduct the research in the area. Two anonymous



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reviewers made important contributions to the manuscript. The research was supported by White Sands National Monument. Boomsma, J. J., and De Vries, A. 1980. Ant species distribution in a sandy coastal plain. Ecol. Entomol. 5: 189-204.
Gall&, L. 1990. Assembly of sand-dune forest ant communities. Memorabilia Zool. 44: 1-6.
. 1991. Structure and succession of ant assemblages in a north European sand dune area. Holarctic Ecol. l4:3 1-37. Gall&, L., and Szonyi, G. 1988. A check list of ants (Hymenoptera: Formicoidea) of a sandy grassland in Kiskunsgg National Park (Hungary). Acta Biol. Szeged. 34: 167-168
Wilson, E. 0. 1955. A monographic revision of the ant genus Lasius. Bull. Mus. Comp. Zool. 1 13: 1-201 + 2 plates.




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