Veromessor lobognathus

Johnson et al., (2022) - Veromessor lobognathus workers are solitary, diurnal foragers that suspend activity when soil temperatures become high (Cole, 1963; Wheeler & Wheeler, 1959). Workers also forage nocturnally (M. Bennett, pers. comm.), presumably when daytime temperatures are consistently high. Nests are usually placed under rocks or workers construct a small tumulus mound in areas where the soil contains numerous small stones (Clark & Blom, 2007; Cole, 1966; Wheeler & Wheeler, 1965). The largest of several excavated colonies contained 627 workers, numerous larvae, and numerous sexuals (55 alate queens, 149 males) (Cole, 1963; Wheeler & Wheeler, 1959), suggesting that colonies contain up to about 1000 workers. Number of reproductive queens in colonies of V. lobognathus is unknown, but two museum series contained two dealate queens (R.A. Johnson, pers. obs.), and Wheeler and Wheeler (1959) found 10 dealate queens in a nest. Additional nests should be excavated to determine if colonies contain multiple reproductive queens.

Wheeler and Wheeler (1986) - We have published 4 articles about this interesting species (Wheeler and Wheeler, 1956, 1959, 1965, 1967); here we give only a sketch of our findings: (1) lobognathus is a characteristic inhabitant of the Pinyon-Juniper Biome, a semiarid environment. (2) In the Dakotas the nests were found only on steep treeless south-facing slopes where much of the surface was bare. The slopes were always near junipers which were on north-facing slopes. Characteristic plants of the habitats were grasses in clumps, low shrubs, yucca, and prickly pear. (3) Nests in the Dakotas were of 2 types: in sandy loam, under large flat stones (average 8 x 46 x 91 cm) which were only slightly buried; where the soil contained numerous small stones there was a small mound of excavated earth around the entrance. (4) The seeds of grasses were harvested. (5) The workers were aggressive and bit tenaciously. (6) We regarded lobognathus as a mimic of Pogonomyrmex occidentalis.

Worker
This species is uniquely characterized by the following combination of features (Johnson et al., 2022):
 * 1) Light to dark orangish-brown to reddish-brown, gaster usually slightly lighter
 * 2) Medial lobe of clypeus with weakly to strongly irregular longitudinal or oblique rugae, medial lobe not thick and protuberant in profile, not elevated above lateral lobes in frontal view
 * 3) Mandibles with 8 teeth
 * 4) Dorsal base of scape flattened and widened; maximum basal width of scape greater than maximum preapical width
 * 5) MOD distinctly less than OMD, OI < 25.0
 * 6) Cephalic dorsum with prominent irregular, longitudinal rugae, usually with numerous short lateral branches, rugae often becoming rugoreticulate posterior to eyes; interrugae on cephalic dorsum moderately punctate to strongly granulate, weakly dull to dull
 * 7) Psammophore moderately well developed; ventral surface of head capsule with both J-shaped hairs and straight or evenly curved hairs, J-shaped hairs arranged in a V-shaped row which does not reach the posterior part of the lateroventral margin of head capsule
 * 8) In dorsal view, pronotum rugoreticulate, sometimes with one to few irregular transverse rugae along anteromedial margin; sides of pronotum with irregular longitudinal rugae with numerous short, lateral branches; mesonotum with strongly irregular longitudinal trending rugae to rugoreticulate; mesopleura with strongly irregular longitudinal rugae, usually with numerous short lateral branches, dorsal one-third often rugoreticulate or nearly so
 * 9) Propodeal spines elongate, slender, straight in profile and weakly curving inward in dorsal view, length 1.0–1.5× the distance between their bases and length > 1.0× MOD; infraspinal facet rugose, weakly shining to smooth and strongly shining; propodeal declivity weakly coriarious, strongly shining
 * 10) Metasternal process small, triangular, longer than high, apex bluntly rounded (Figures 12B, 34).

Queen
This caste is diagnosed by the following combination of features (Johnson et al., 2022):
 * 1) Light to dark orangish brown to reddish-brown, gaster usually slightly darker
 * 2) Medial lobe of clypeus with coarse, irregular rugae that traverse in all directions, anteromedial margin sometimes sharply depressed
 * 3) Mandibles with 8 teeth
 * 4) Dorsal base of scape flattened and widened; maximum basal width of scape greater than maximum preapical width
 * 5) MOD slightly less than to slightly greater than OMD
 * 6) Cephalic dorsum with wavy to irregular longitudinal rugae, medial rugae not diverging to diverging toward posterior corners, rugae often becoming more irregular to weakly rugoreticulate along posterior margin; interrugae strongly punctulate and roughened, dull to weakly shining,
 * 7) Psammophore moderately well developed
 * 8) Sides of pronotum weakly coriarious, weakly shining between longitudinal rugae; mesoscutum with longitudinal rugae; mesoscutellum finely striatopunctate with scattered fine, irregular rugae; anepisternum moderately shining between fine longitudinal rugae; katepisternum weakly coriarious, weakly shining with few short rugae near margins
 * 9) Propodeum with regular to irregular longitudinal and oblique rugae, propodeal spines elongate-triangular, acuminate, length slightly less than distance between their bases; infraspinal facet weakly coriarious, weakly shining; propodeal declivity smooth and shining
 * 10) Metasternal process longer than high, apex broadly rounded (Figure 35)

Male
This caste is diagnosed by the following combination of features (Johnson et al., 2022):
 * 1) Light brown to brownish black
 * 2) Medial lobe of clypeus thick and abruptly descendant at anteromedial margin; anterior margin nearly straight across middle
 * 3) Mandibles usually with 1 (rarely 2) denticles basad of preapical tooth
 * 4) Ocelli well above level of top of eyes
 * 5) Anepisternum moderately shining, weakly punctulate between fine, longitudinal striae that are often lacking on lower one-fourth or more or entire anepisternum mostly smooth and shining; katepisternum with short rugae near margins, rest of katepisternum weakly to moderately coriarious or entire katepisternum mostly smooth and shining
 * 6) Propodeum weakly to moderately coriarious between moderately coarse longitudinal rugae to mostly smooth and shining with weaker longitudinal rugae; spines or denticles absent; in profile, juncture of dorsal surface and propodeal declivity weakly angulate to rounded
 * 7) Metasternal process low and obtuse to acute
 * 8) Subpetiolar process prominent and acute (Figures 1F, 36)

Identification Notes
Veromessor lobognathus is broadly sympatric with several congeners including V. smithi, V. lariversi and V. pseudolariversi. Workers of Veromessor lobognathus are separated from V. smithi based on: (1) propodeal spines longer, length greater than distance between their bases and length > 1.0× MOD, and (2) eyes smaller (MOD = 0.31–0.41, OI = 20.5–25.0). In V. smithi: (1) propodeal spines short, length less than distance between their bases and length < 0.5× MOD, and (2) eyes larger (MOD = 0.38–0.49, OI = 24.8–33.5).

Veromessor lobognathus is separated from workers of V. lariversi and V. pseudolariversi based on: (1) light to dark orangish-brown to reddish-brown head and mesosoma, (2) maximum basal width of scape greater than maximum preapical width, and (3) mandibles with 8 teeth. For both V. lariversi and V. pseudolariversi: (1) body concolorous light yellowish to yellowish-orange or yellowish-red, (2) maximum basal width of scape less than maximum preapical width, and (3) mandibles with 7 teeth.

A molecular phylogeny that used UCEs shows V. lobognathus and V. smithi are sister lineages (M.L. Borowiec, unpub. data).

Distribution
Veromessor lobognathus is a mostly mid-elevation species that occurs at 1,060–2,275 m, and it is generally found at higher elevations in western portions of its range (Wheeler & Wheeler, 1965). It appears to be most common in pinyon pine-juniper habitats similar to those occupied by Veromessor smithi, but it also occurs in rockier foothill habitats, especially in eastern portions of its range. This species occurs in the Great Basin shrub steppe, Snake-Columbia shrub steppe, Colorado Plateau shrublands, Western short grasslands, and Northern short grasslands ecoregions, as defined by Olson et al. (2001). Incursions into the Mohave Desert are restricted to higher elevations, such as Rainier Mesa on the Nevada Test Site (Figure 27C) (Johnson et al., 2022).

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

Biology


The following notes are provided by Johnson et al. (2022):

The chemistry of several glands has been examined in workers of V. lobognathus. The mandibular and venom glands lack volatile compounds, while the postpharyngeal gland contained linear and methyl-branched higher hydrocarbons, and the Dufour gland contained a mixture of hydrocarbons (do Nascimento, Jackson, Morgan, Clark, & Blom, 1993). Like other small-colony congeners, workers of V. lobognathus have a small pygidial gland reservoir and lack a textured tergal cuticle (Hölldobler et al., 2013).

Mating flights have not been observed, but sexuals have been collected in nests from 24 June–2 August, suggesting that flights occur during summer (probably late June through July).

Nomenclature

 * . Messor lobognathus Andrews, 1916: 82, fig. 1 (w.) U.S.A. (Colorado).
 * Type-material: 4 syntype workers.
 * Type-locality: U.S.A.: Colorado, Glenwood Springs, 5750 ft (T.D.A. Cockerell).
 * Type-depository: MCZC.
 * Wheeler, G.C. & Wheeler, J. 1957c: 142 (l.); Cole, 1963: 680 (q.m.).
 * combination in Messor: Bolton, 1982: 341 (in text);
 * combination in Veromessor: Wheeler, W.M. & Creighton, 1934: 371; Ward, et al. 2015: 73.
 * Status as species: Wheeler, W.M. & Creighton, 1934: 371 (redescription); Enzmann, J. 1947b: 152 (in key); Creighton, 1950a: 160; Smith, M.R. 1951a: 799; Gregg, R.E. 1955b: 45; Smith, M.R. 1956a: 37 (in key); Wheeler, G.C. & Wheeler, J. 1957c: 140; Smith, M.R. 1958c: 119; Cole, 1963: 680; Cole, 1966: 11 (in key); Smith, M.R. 1967: 353; Yensen, et al. 1977: 183; Smith, D.R. 1979: 1364; Allred, 1982: 507; Wheeler, G.C. & Wheeler, J. 1986g: 39; Bolton, 1995b: 255.
 * Distribution: U.S.A.

Type Material

 * Lectotype worker (designated by Johnson et al., 2022: 61) from Glenwood Springs, Colorado, United States, 5,750’, no date (T.D.A. Cockerell) [CASENT0105632] [USNM].
 * Paralectotype, 1 worker [MCZC], UNITED STATES, Colorado: Glenwood Springs, 5,750’, no date (T.D.A. Cockerell).

Worker
Wheeler and Creighton (1934) – Length 6 mm.

Head subquadrate, as broad as long (mandibles excluded), the sides approximately straight, a trifle narrower in front of the eyes than behind them. Occiput flat, with the occipital angles broadly and evenly rounded. Anterior margin of the very short clypeus straight, with a shallow V-shaped median impression. Eyes oval, moderately large and feebly convex, placed at the middle of the sides of the head. Mandibles large and strongly convex in two planes, so that the lobed tip of the masticatory margin is carried back beneath the mandible and is not noticeable unless viewed from a point in front of the lower margin. This lobe, which appears to consist of three fused teeth, is sharply set off from the remainder of the masticatory margin. Frontal carinae subparallel, rather thick and short, with a welt-like portion which extends from the anterior end encircling the front of the antennal fossa. Antennal scapes in repose surpassing the occipital border by an amount slightly in excess of their greatest thickness, the basal end of the scape flattened and strongly spatulate. Distal to the flattened portion the diameter of the scape gradually increases toward the slightly swollen tip. First and last funicular joints of equal length, the remaining joints all much shorter; the diameter of the funicular joints gradually increases distally, so that no distinct club is formed although the apical are almost twice as thick as the basal joints.

Dorsum of promesonotum, seen in profile, evenly and moderately convex; the mesoepinotal suture with a broad, flattened impression whose posterior boundary is marked by a slight ridge on the basal face of the epinotum'. Basal face of the epinotum flat and feebly sloping, forming a sharp angle with the shorter declivous face, their angle armed with two spines of moderate length. Seen from above, the promesonotum is pyriform and notably broader than the remainder of the thorax; the mesoepinotal suture forms a narrow slot-like groove between the mesonotum and epinotum without constriction of the sides in that area. Epinotal spines feebly divergent and very slightly incurved, their length slightly more than half the distance between their tips.

Petiole, seen in profile, with a thick anterior peduncle whose dorsum forms a continuous slope with the anterior face of the node. Lower surface of the peduncle with a small ,anterior tooth. Node of the petiole small and low with a flattened summit, which slopes backwards to the short posterior face. Posterior peduncle short and very thick. Postpetiole in profile with a feebly convex dorsum and a well-marked impression in the middle of the ventral surface, the posterior portion slightly constricted at its junction with the gaster. Seen from above, the sides of the petiole are parallel as far forward as the two rather prominent spiracles, anterior to which the peduncle is much narrowed by a semicircular impression at either side. Postpetiole almost twiee as wide as the petiole, subtriangular. Gaster rather large, oval. Legs long, the femora somewhat incrassated.

Mandibles shining, with rather coarse but shallow longitudinal striae. Clypeus granulose, subopaque. Frontal area shining. Head opaque, completely covered with fine longitudinal rugae, the interrugal spaces coriaceous. Rugae along the median portion of the head not divergent, the lateral rugae encircling the eye. Antennal scapes finely granulose, feebly shining. Thorax slightly shining, the rugae with which it is completely covered more irregular and coarser than those of the head. Petiole and postpetiole finely granulose, opaque. Gaster and legs shining.

Hairs moderately abundant, stout, erect, and golden. Gular ammochaetae moderately developed, the inner row of long curved hairs flanked at the side by additional hairs which are shorter and less regularly placed. Inner surface of the mandibles with numerous long hairs, those on the outer surface short, fine, and suberect. Clypeus with a fringe of long curved hairs. Except for two or three long hairs on the front, the remainder of the head is covered with short, stout, and rather blunt hairs of fairly uniform length. Hairs on the pronotum about equal in length and abundance to those on the occiput. Hairs on the epinotum much sparser. Petiole with a tuft of very coarse hairs arising from the posterior face of the node. Dorsum of the postpetiole with numerous coarse, long hairs; those of its lower surface, shorter, sparser, and much finer. Hairs on the gaster relatively sparse, uniformly distributed over the first segment; over the rest of the gaster confined to an irregular row at the posterior edge of the segment. Femora with sparse, short, erect hairs; those of the tibiae, tarsi, and antennal scapes shorter, much more numerous, and suberect. Hairs on the funiculi very fine, grading into pubescence toward the tips.

Color clear orange yellow, the posterior gastric segments, except the terminal segment, which bears a castaneous band, somewhat lighter than the remainder of the body. Clypeus and mandibles tinged with brown, the masticatory margin of the mandibles piceous.

References based on Global Ant Biodiversity Informatics

 * Allred D. M. 1982. Ants of Utah. The Great Basin Naturalist 42: 415-511.
 * Allred, D.M. 1982. The ants of Utah. Great Basin Naturalist 42:415-511.
 * Cole A. C., Jr. 1963. A new species of Veromessor from the Nevada Test Site and notes on related species (Hymenoptera: Formicidae). Annals of the Entomological Society of America 56: 678-682.
 * Gregg, R.T. 1963. The Ants of Colorado.
 * Johnson R. Personnal Database. Accessed on February 5th 2014 at http://www.asu.edu/clas/sirgtools/resources.htm
 * La Rivers I. 1968. A first listing of the ants of Nevada. Biological Society of Nevada, Occasional Papers 17: 1-12.
 * Smith M. R. 1956. A key to the workers of Veromessor Forel of the United States and the description of a new subspecies (Hymenoptera, Formicidae). Pan-Pacific Entomologist 32: 36-38.
 * Wheeler G. C., and J. Wheeler. 1957. Veromessor lobognathus in North Dakota (Hymenoptera: Formicidae). Psyche (Camb.) 63: 140-145.
 * Wheeler G. C., and J. Wheeler. 1965. Veromessor lobognathus: third note (Hymenoptera: Formicidae). Journal of the Kansas Entomological Society 38(1): 55-61.
 * Wheeler G. C., and J. Wheeler. 1986. The ants of Nevada. Los Angeles: Natural History Museum of Los Angeles County, vii + 138 pp.
 * Wheeler G. C., and J. Wheeler. 1987. A Checklist of the Ants of South Dakota. Prairie Nat. 19(3): 199-208.
 * Wheeler, G.C. and J. Wheeler. 1988. A checklist of the ants of Montana. Psyche 95:101-114