Veromessor lobognathus (Andrews, 1916)

Johnson, Robert A., Borowiec, Marek L., Snelling, Roy R. & Cole, Arthur C., 2022, A taxonomic revision and a review of the biology of the North American seed-harvester ant genus Veromessor (Hymenoptera: Formicidae: Myrmicinae), Zootaxa 5206 (1), pp. 1-115 : 61-67

Veromessor lobognathus

( Figures 1F , 12B , 34–36 )

Distribution— Figure 27C

Messor lobognathus Andrews, 1916: 82 , fig. 1 (worker). Syntypes examined: 1 worker [ MCZC], 1 worker [ USNM], UNITED STATES, Colorado: Glenwood Springs, 5,750’, no date (T.D.A. Cockerell); Cole, 1963: 680 (queen, male); Wheeler and Wheeler, 1957: 143, figs. 1b, 2 (larvae). See also Wheeler and Creighton, 1934: 371, plate II, fig. 6. USNM worker here designated LECTOTYPE [CASENT0105632].

Veromessor lobognathus (Andrews) ; Wheeler and Creighton, 1934: 362 (first combination in Veromessor ).

Messor lobognathus Andrews ; Bolton, 1982: 341 (revived combination in Messor ).

Veromessor lobognathus (Andrews) ; Ward, Brady, Fisher, and Schultz: 2015: 13 (revived combination in Veromessor ).

Lobognathus Enzmann, 1947 ; 152 [as subgenus of Veromessor ]. [Erroneous entry for Veromessor lobognathus (Andrews) ; see Brown, 1949: 49].

Worker diagnosis. This species is uniquely characterized by the following combination of features: (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, and (10) metasternal process small, triangular, longer than high, apex bluntly rounded ( Figures 12B , 34 ).

Measurements. lectotype (n = 38). HL 1.77 (1.30–1.69); HW 1.85 (1.28–1.82); MOD 0.35 (0.31–0.41); OMD 0.53 (0.34–0.49); SL 1.54 (1.20–1.54); PNW 1.10 (0.79–1.10); HFL 2.22 (1.41–1.98); ML 2.28 (1.61–2.29); PW 0.36 (0.26–0.36); PPW 0.53 (0.44–0.60). Indices: SI 83.24 (78.95–97.66); CI 104.52 (98.46–118.12); OI 21.08 (20.47–25.00); HFI 120.00 (105.00–120.00).

Queen diagnosis. This caste is diagnosed by the following combination of features: (1) light to dark orangishbrown 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, and (10) metasternal process longer than high, apex broadly rounded ( Figure 35 ).

Measurements. (n = 12). HL 1.48–1.86; HW 1.65–1.99; MOD 0.39–0.52; OMD 0.35–0.47; SL 1.30–1.62; HFL 1.78–2.10; ML 2.49–2.91; PW 0.37–0.42; PPW 0.69–0.74. Indices: SI 76.57–84.57; CI 102.98–114.86; OI 22.61–26.67; HFI 99.48–112.64.

Male diagnosis. This caste is diagnosed by the following combination of features: (11) light brown to brownishblack, (12) medial lobe of clypeus thick and abruptly descendant at anteromedial margin; anterior margin nearly straight across middle, (13) mandibles usually with 1 (rarely 2) denticles basad of preapical tooth, (14) ocelli well above level of top of eyes, (15) 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, (16) 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, (17) metasternal process low and obtuse to acute, and (18) subpetiolar process prominent and acute ( Figures 1F , 36 ).

Measurements. (n = 12). HL 0.82–0.96; HW 0.77–0.86; MOD 0.33–0.38; OMD 0.09–0.12; SL 0.34–0.46; HFL 1.73–1.99; ML 2.13–2.58; PW 0.28–0.34; PPW 0.54–0.61; AOD 0.09–0.11; IOD 0.24–0.31; OOD 0.27–0.30. Indices: SI 43.59–59.74; CI 84.78–100.00; OI 39.76–46.15; HFI 205.95–246.15.

Additional material examined. UNITED STATES: Arizona: Navajo Co.: Black Mesa, 1991 m, Jul 21, 2008 (MCZC). Colorado: Larimer Co.: Owl Canyon near Hwy 287, 5700’ & 6100’, Jul 22, 1952 (LACM; USNM). Rio Blanco Co.: 20 mi SW Rangely, 6500’, Aug 26, 1952 (not examined, see Gregg, 1955). Idaho: Bingham Co.: INEL (= Idaho National Laboratory) at East Butte (T2N, R32E, Sect 14), 1957 m, May 30, 1987 (CIDA; RAJC); INEL at Middle Butte (T2N, R32E, Sect 20), 5550’ & 6100’, Jun 24, 1989 (CIDA; RAJC); T3N, R33E, Sect 24, 1528 m, Jun 1, 1993 (CIDA); INE at 2.2 mi NE Jct. Hwy 20/Rd T-21, 1528 m, Jun 1, 1993 (RAJC). Butte Co.: AEC-NRTS (=Idaho National Laboratory), Jun 29, 1967 (CIDA); AEC-NRTS at 30 mi W Idaho Falls, 4947’, Jun 14, 1967 (LACM); T2N, R28E, Sect 23NE, at 44 km ESE Arco, 1518 m, May 28, 1987 (CIDA); INEL (T2N, R29E, Sect 1), 1503 m, May 22, 1987 & Jul 1, 1989 & Aug 13, 1989 & Jul 6, 1990 (CIDA; RAJC); Road T-11 (T3N, R28E, Sect 1), 1561 m, May 29, 1993 (CIDA); INEL at W border on Road T-2 (T3N, R28E, Sect 18), 1615 m, Jun 22, 1988 (CIDA); INEL at dead end of Road T-2 (T3N, R28E, Sect 19), 5275’, Jun 22, 1988 (CIDA); 1 mi S Teakettle Butte (T2N, R28E, Sect 19), 1584 m, May 31, 1993 (CIDA; RAJC); Rd T-10 (T3N, R28E, Sect 32), 1567 m, Jun 22, 1988 (CIDA); T3N, R29E, Sect 7, 1567 m, May 29, 1993 (CIDA); INEL on Road T-12 (T3N, R29E, Sect 33), 1588 m, Jun 2, 1993 (CIDA); INEL at Powerline Rd (T4N, R30E, Sect 14), 1417 m, Jul 6, 1990 (CIDA); INEL at hilltop above Hwy 33 (T5N, R30E, Sect 3), 4987’, Jun 23, 1988 (CIDA); INEL at 1 km W Jct Franklin & Lincoln Blvds (T5N, R31E, Sect 4), 1462 m, Jun 9, 1991 (CIDA); INEL at site boundary on Kyle Road Canyon (T6N, R30E, Sect 3), 5440’, May 27, 1988 (CIDA; RAJC); 15.7 km ENE Howe (T6N, R30E, Sect 24), 1481 m, Jul 3, 1987 (CIDA); 2 km SSW Howe, 1510 m, Aug 24, 2017 (JTLC); INEL at N Big Lost Sinks (T6N, R30E, Sect 27), 1554 m, Jul 8, 1990 (CIDA); INEL at Richard Butte (T7N, R31E, Sect 4), 1554 m, Jul 7, 1990 (CIDA; RAJC). Clark Co.: INEL at W border (T8N, R30E, Sect 36), 1615 m, Jun 9, 1991 (CIDA; RAJC); INEL at Hwy 28 at 1 mi SE Jct Hwy 22 (T8N, R31E, Sect 36), 1536 m, Jun 9, 1991 (CIDA); 1 mi E Jct Hwys 28 & 22 (T8N, R31E, Sect 35), 5040’, Sep 1, 1991 (CIDA); INEL at Hwy 22 (T8N, R31E, Sect 34), 1554 m, Jun 29, 1988 (CIDA); INEL at Hwy 28 (T8N, R31E, Sect 36), Sep 1, 1991 (CIDA). Jefferson Co.: INEL at Rd T-4 (T4N, R33E, Sect 13), 1533 m, Jul 3, 1989 (CIDA; RAJC); INEL Rd T-2 (T4N, R33E, Sect 17), 5010’, Jun 14, 1994 (CIDA); T6N, R32E, Sect 15, 1460 m, Jun 1, 1993 (CIDA); INEL along Hwy 28 (T7N, R32E, Sect 11), 1253 m, Jun 9, 1991 (CIDA); INEL at 0.9 mi N Hwy 33 (T6N, R32E, Sect 15), 4820’, Jun 1, 1993 (RAJC). Montana: Carter Co.: 10 mi SW Ekalaka (T1N, R57E), 3500’, Jun 13, 1966 (UAIC). Nevada: Elko Co.: Palomino Ridge, 6300’, Jul 15, 1970 (LACM: RAJC). Humboldt Co.: 91 mi SSW Denio (T42N, R27E, Sect 11), 5200’, May 24, 1971 (LACM). Lyon Co.: 14 mi SSE Yerington, 5100’, May 20, 1971 (LACM; RAJC); 16 rd mi SSE Yerington, 5200’, Jun 16, 1979 (LACM); Pine Grove Rd at 0.9 mi S Jct Hwy 208, 4610’, Jul 22, 2018 (NHMW; RAJC). Nye Co.: Currant Pass Summit (18 mi NE Currant), 6500’, May 5, 1974 (LACM); AEC-NTS near Mercury (= Ranier Mesa), 7000’, Jun 21–Jul 26, 1962 (LACM; UAIC; USNM); Morey Mine in Hot Creek Valley, 7100’, Jun 18, 1970 (LACM); Nye, 9 km NNW Belmont, 2505 m, Jul 12, 2019 (UCDC). Storey Co.: 2 mi E Clark, 4700’, Jul 20, 1971 (LACM); Clark Mine at 27 km E Sparks, 1420 m, Jul 3, 1994 (RAJC); 20 km WSW Fernley, 1430 m, Jul 3, 1994 (UCDC). Washoe Co.: Hanging Rock Canyon, 1750 m, Jun 5–6, 1999 (UCDC). White Pine Co.: Ely, Jun 25, 1954 (LACM; USNM); T18N, R64E, 7000’ & 7500’, Jul 15, 1970 (LACM); White Pine Mtns (T17N, R57E, Sect 17), 6700’, Apr 29, 1971 (LACM); White Pine Mtns, T 17N, R57E, Sect 22, 6700’, Apr 29, 1971 (RAJC); 2 mi E McGill, 7500’, Jul 15, 1970 (RAJC); 49 km N Ely, 2005 m, Jul 14, 2019 (UCDC). North Dakota: Billings Co.: Roosevelt National Park near Medora, May 12, 1954 & Jun 28, 1957 & Jul 5, 1957 & Jun 1–13, 1958 & Aug 2, 1958 & Jun 10, 1960 (LACM; USNM); Roosevelt National Park, T140N, R102W, Sect 1, May 28, 1957 (LACM; USNM); Roosevelt National Park, T140N, R102W, Sect 12, May 9–10, 1960 (LACM). Oregon: Malheur Co.: 7.0 mi ENE Jct Hwys 78 & 95, 1095 m, Jun 21, 2020 (MLBC). South Dakota: Custer Co.: T3S, R1E, Sect 18, 4750’, Jun 10–15, 1963 (UAIC). Utah: Duchesne Co.: 11 mi W Duchesne (T3S, R6W), 6200’, no date (not examined, see Wheeler & Wheeler, 1967). Millard Co.: Valley in House Range, 2235 m, Apr 7, 2013 (JTLC); House Range at Notch Peak, 2230 m, Apr 7, 2013 (JTLC). Piute Co.: Tushar Mtns, 1.8 mi S Jct Rt 89 & FSR 125, Jul 21, 2009 (MCZC). Uinta Co. : 15 km NNE Vernal, 1720 m, Jul 15, 2013 (JTLC) ( Figure 27C ).

Etymology. The specific epithet, lobognathus , (Gr. lobos = lobed, and gnathos = jaw) presumably refers to the mandibles, which Andrews described as “large and stout, peculiarly lobed apically.”

Discussion. 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).

Biology. 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.

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).

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 V. 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 ).

Figures

FIGURE 1. Photographs of the metasternal process on males of Veromessor: (A) V. andrei (CASENT4010823), (B) V. chamberlini (UCRC_ENT00500152), (C)V.chicoensis (CASENT0869853), (D) V.julianus (LACMENT359792),(E)V.lariversi (CASENT0761204), (F) V. lobognathus (LACMENT363986), (G) V. pergandei (CASENT0869850), (H) V. pseudolariversi (CASENT0869851), (I) V. smithi (LACMENT364071), and (J) V. stoddardi (LACMENT364102). Photographs by Robert Johnson from www.AntWeb.org.

FIGURE 12. Photographs of dorsal surface of scape: (A) Veromessor chamberlini (LACMENT359743)—anterior edge of scape curving inward distad of base (red arrow), posterior edge of scape flat to weakly convex at base (black arrow), narrowing distad of base; widened area at base of scape much longer than width at base, and (B) V. lobognathus (LACMENT363932)—anterior edge of scape flat at base (red arrow), posterior edge of scape narrowing from base (black arrow); widened area at base of scape shorter than width at base. Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 27. Geographic distribution of: (A) Veromessor julianus, (B) V. lariversi, and (C) V. lobognathus. The larger black circle in each panel denotes the type locality.

FIGURE 34. Photograph of Veromessor lobognathus worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (MCZ-ENT00736317). Photographs by Wade Lee from www.AntWeb.org.

FIGURE 35. Photograph of Veromessor lobognathus alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922832). Photographs by Michele Esposito from www.AntWeb.org.

FIGURE 36. Photograph of Veromessor lobognathus male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0922830). Photographs by Michele Esposito from www.AntWeb.org.