Veromessor pseudolariversi Johnson, Borowiec, Snelling & Cole, 2022

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 : 80-86

Veromessor pseudolariversi Johnson, Borowiec, Snelling & Cole NEW SPECIES

( Figures 1H , 29D–F , 42–44 )

Distribution— Figure 41B

Holotype worker [ USNM: CASENT0923119 ]: UNITED STATES, Nevada: Nye County, 7 mi SSE Beatty, 36 o 49’N 116 o 44’W, 3000’ (909 m), 5 April 1970 (G.C. & J. Wheeler NEV#782A) . Paratypes, same data as holotype: CASC (10 workers) , LACM (19 worker), MCZC (12 workers), MLBC (6 workers), NHMW (2 workers), RAJC (40 workers), UAIC (6 workers), UCDC (6 workers), USNM (16 workers).

Veromessor lariversi: Cole, 1963: 680 , figs. 1b, 2b, 3b (queen, male), description apparently used V. pseudolariversi that was misidentified as V. lariversi (see discussion under V. lariversi ).

Veromessor lariversi: Holldobler et al., 2013: 866 , misidentified as V. lariversi .

Worker diagnosis. This species is uniquely characterized by the following combination of features: (1) light yellowish to yellowish-orange or yellowish-red, gaster sometimes slightly darker, (2) medial lobe of clypeus arugose, smooth and shining, not thick and protuberant in profile, not elevated above lateral lobes in frontal view, (3) mandibles with 7 teeth, (4) dorsal base of scape not flattened, slightly widened; maximum basal width of scape less than maximum preapical width, (5) MOD distinctly greater then OMD, OI> 32.0, (6) cephalic dorsum mostly smooth and shining with scattered piligerous punctures between few discontinuous, medial longitudinal rugae that weaken laterally and disappear posterior to eyes, posterior margin smooth and shining, rugae more coarse and well-defined in front of eyes, (7) psammophore well developed; consisting of J-shaped hairs arranged in a distinct row around the outer margin of ventral surface of the head capsule, (8) dorsum of pronotum weakly roughened and shining to lineogranulate or with few weak discontinuous irregular transverse rugae; sides of pronotum weakly to moderately punctulate-granulate, weakly shining, between few coarse longitudinal rugae; mesonotum with piligerous punctures to moderately punctulate-granulate, weakly shining to shining; mesopleura with moderately coarse, wavy to irregular, longitudinal rugae, (9) sides of propodeum weakly to moderately punctulate-granulate between few longitudinal or oblique rugae; propodeal spines divergent, elongate-triangular, acuminate, length similar to width at base, less than the distance between their bases, and length <0.5× MOD; infraspinal facet weakly coriarious, weakly shining; propodeal declivity smooth and shining, and (10) metasternal process higher than long, apex subangulate. Additionally, in profile, the anteroventral margin of postpetiole interrupted by a transverse ridge, appearing as a minute process, margin weakly concave anterior to process ( Figures 29D–F , 42 ).

Measurements. holotype (n = 26 + 9 paratypes). HL 1.16 (1.02–1.25); HW 1.11 (1.00–1.18); MOD 0.41 (0.35– 0.41); OMD 0.28 (0.24–0.32); SL 1.04 (0.86–1.10); PNW 0.74 (0.65–0.78); HFL 1.25 (0.98–1.28); ML 1.46 (1.37– 1.58); PW 0.22 (0.18–0.24); PPW 0.35 (0.29–0.37). Indices: SI 93.69 (74.78–99.00); CI 95.69 (87.83–101.92); OI 36.94 (32.14–37.61); HFI 112.61 (94.94–118.10).

Description. Head quadrate to longer than wide (CI = 87.83–101.92); posterior margin flat to weakly convex in full-face view. Medial area of cephalic dorsum mostly smooth and shining with faint to weakly prominent, wavy to weakly irregular rugae laterad to near posterior margin of eyes; cephalic rugae most prominent between frontal lobes and eyes and on malar area, usually with one to two rugae continuing posterad along dorsal and ventral margins of eyes. Scattered piligerous punctures on posterior one-half of cephalic dorsum. Interrugae on cephalic dorsum weakly shining to shining; posterior corners weakly roughened to weakly coriarious, weakly shining to smooth and shining. Medial lobe of clypeus weakly convex, arugose, weakly coriarious, weakly shining to smooth and shining with numerous long, curved, bristle-like, yellowish macrochaetae projecting from anterior margin and lateroventral margin of mandibles. Mandibles with seven teeth. Eyes large (MOD = 0.35–0.41 mm; 0.30–0.36× HL; OI> 32.0). In profile, eyes situated near middle of head; eyes distinctly larger than OMD (OMD = 0.63–0.89× MOD). In full-face view, eyes protruding beyond lateral margins of head. Antennal scapes (SI = 74.78–99.00) surpassing posterior corners of head by slightly less than length of first funicular segment. Dorsal base of scape not flattened to weakly flattened, weakly widened; maximum basal width of scape less than maximum preapical width. Psammophore well developed; consisting of J-shaped hairs arranged in a distinct row around the outer margin of the ventral region of head capsule.

Promesonotal profile strongly convex with promesonotal suture weakly to moderately impressed. Dorsum of pronotum weakly roughened and shining to lineogranulate or with several weak irregular, discontinuous, transverse rugae anterad; sides of pronotum moderately to strongly granulate-punctulate, weakly shining, between several irregular, discontinuous, mostly vertical rugae that are usually restricted to anterior one-half. Mesonotum moderately to strongly punctulate-granulate or coriarious, weakly shining; mesopleura with moderately coarse, wavy to irregular rugae that traverse longitudinally to posterodorsally. Sides of propodeum weakly to moderately punctulate-granulate between few longitudinal or oblique rugae that continue from mesopleura but weaken or disappear on sides of propodeum; propodeal spines divergent, elongate-triangular, acuminate, length similar to width at base, less than distance between their bases, and <0.5× MOD; infraspinal facet lacking a well-defined keel, weakly coriarious, weakly shining; propodeal declivity smooth and shining. Propodeal spiracles circular facing posterad. Legs weakly to moderately coriarious, weakly shining to smooth and shining.

In profile, peduncle of petiole long, thickening posterad, meeting anterior surface of petiolar node in a broadly continuous curve. In profile, posterior surface of petiolar node strongly convex; petiolar node asymmetrical with anterior surface longer than posterior surface, apex weakly rounded to weakly subangulate. In dorsal view, petiolar node about as long as wide, narrowing to a broadly rounded anterior margin. Sides and posterior surface of petiolar node weakly sculptured to coriarious, weakly shining. Dorsum of postpetiole convex in profile; in dorsal view, sides subparallel posterad, narrowing anterad; length and width similar; dorsum weakly sculptured to weakly punctulategranulate, weakly shining to smooth and shining; in profile, ventral margin of postpetiole discontinuous with margin interrupted by a minute process anterad, margin weakly concave anterior to process. First gastral tergum weakly to moderately coriarious, weakly shining to shining.

Erect, mostly short to medium-length, yellowish pilosity sparse on head. Moderately abundant semidecumbent to decumbent pilosity on scape, becoming slightly denser distally; abundant decumbent hairs on funicular segments. In profile, dorsum of mesosoma with up to 10–12 erect, yellowish hairs, longest hairs about 0.3× MOD. Hairs on gastral terga short, sparse, arising from piligerous punctures. Legs with moderately abundant suberect to decumbent, yellowish setae. Body mostly concolorous yellowish-orange to orangish-yellow, gaster often slightly more yellowish to yellowish-brown ( Figures 29D–F , 42 ).

Queen diagnosis. This caste is diagnosed by the following combination of features: (1) mostly concolorous yellowish-brown to medium orangish-brown, (2) medial lobe of clypeus not thick and protuberant in profile, not elevated above lateral lobes in frontal view, medial lobe mostly smooth and arugose with numerous micropunctures to coriarious, (3) mandibles with 7 teeth, (4) dorsal base of scape weakly flattened, weakly widened; maximum basal width of scape less than maximum preapical width, (5) MOD distinctly greater than OMD, (6) cephalic dorsum with prominent longitudinal rugae adjacent to midline, above and below eyes, and on malar area; rugae lacking posterior to ocelli, posterior margin mostly smooth and shining, (7) psammophore well developed, (8) sides of pronotum moderately granulate between fine longitudinal rugae; mesoscutum smooth and shining, sometimes with faint rugae and scattered piligerous punctures; mesoscutellum smooth and strongly shining; mesospleura roughened and dull between wavy mostly longitudinal rugae, rugae faint to disappearing along posterodorsal margin of katepisternum, (9) propodeum moderately coriarious between longitudinal and oblique rugae; propodeal spines triangular, about as long as width at base, length shorter than the distance between their bases; infraspinal facet and propodeal declivity weakly coriarious, weakly shining to shining, and (10) metasternal process higher than long, apex rounded. Additionally, in profile, the anteroventral margin of postpetiole interrupted by a transverse ridge, appearing as a minute process, margin weakly concave anterior to process ( Figure 43 ).

Measurements. (n = 3). HL 1.22–1.31; HW 1.21–1.36; MOD 0.43–0.48; OMD 0.25–0.27; SL 1.0–1.11; HFL 1.30–1.32; ML 1.95–2.04; PW 0.29–0.31; PPW 0.45–0.48. Indices: SI 81.62–85.95; CI 96.95–107.09; OI 33.86– 39.67; HFI 96.32–109.09.

Male diagnosis. This caste is diagnosed by the following combination of features: (11) dark brownish-black, (12) medial lobe of clypeus with several irregular longitudinal rugae with prominent medial carina that bifurcates near anterior margin, (13) preapical tooth small; mandibles with 1–2 minute teeth basad of preapical tooth, (14) in frontal view, anterior ocellus slightly above level of top of eyes, (15) mesopleura dull to weakly shining; anepisternum with fine longitudinal rugae, katepisternum with fine rugae that traverse ventrally from anterodorsal margin then curve posterad to posterior margin, (16) propodeum with moderately strong rugae, interrugae moderately coriarious; propodeal spines consist of denticles, (17) metasternal process elongate, digitiform, and (18) subpetiolar process triangular, slightly longer than high.Additionally, in profile, ventral margin of postpetiole discontinuous with margin interrupted by a minute process anterad, margin weakly concave anterior to process ( Figures 1H , 44 ).

Measurements. (n = 4). HL 0.81–0.88; HW 0.86–0.96; MOD 0.44–0.48; OMD 0.080–0.12; SL 0.32–0.41; HFL 1.50–1.59; ML 2.14–2.22; PW 0.33–0.37; PPW 0.51–0.52; AOD 0.07–1.08; IOD 0.22–0.27; OOD 0.27–0.28. Indices: SI 36.78–46.51; CI 101.16–109.88; OI 49.44–51.16; HFI 164.58–178.65.

Additional material examined. UNITED STATES: California: Inyo Co. : 2 mi W Lone Pine , 4300’, Jul 17, 1952 ( CASC) ; 3 mi W Lone Pine , 4300’, May 2–3, 1952 & Jul 17, 1952 & Apr 7, 1959 ( LACM; MCZC; UAIC; USNM) ; Alabama Hills at 4.7 mi W Lone Pine, 5080’, May 23, 2008 ( RAJC) ; Jct Hwy 190 & Saline Valley Rd, 4860’, May 24, 2008 ( RAJC) . Lassen Co.: 13 km at 9.5 o N Doyle , 1240 m, Jun 27, 2004 ( UCDC) . Nevada: Churchill Co.: T24N, R26E, Sect 8, 4500’, Jun 10, 1975 ( LACM) ; Fairview Valley at Jct Hwys 31 & 50, 4100’, May 17, 1971 ( LACM) . Esmeralda Co. : Goldfield , 5800’, Oct 19, 1952 ( LACM) . Lyon Co.: 0.2 mi NW Jct Hwy 477 & I-80, 4120’, Jul 24–25, 2018 ( RAJC) ; 2 mi ESE Silver Springs , 4000’, Jul 18, 1973 ( LACM) ; Mason Valley at 0.6 mi S Jct Hwy 208 & Pine Grove Rd , 4490’, Sep 8, 2014 ( RAJC) ; 6 mi S Mason , 4400’, May 20, 1971 ( LACM) ; 2 km SW Weeks , 1280 m, Jul 2, 2006 ( UCDC) ; Fort Churchill State Historic Park , 1285 m, Jul 2, 1996 & Jul 1–2, 2010 & & Jul 3, 2008 & Jul 2, 2012 & Jul 29, 2016 ( MLBC; MMPC; UCDC) . Mineral Co.: Petrified Summit , 6200’, Jun 26, 1970 ( LACM) . Nye Co.: Wagner , 4000’, Oct 17, 1952 ( LACM) ; near Mercury , Jul 4–11, 1962 ( LACM) ; Big Dune at 10 mi W Lathrop Wells, May 31, 1970 ( LACM) . Pershing Co.: 7 Devils Spring , 3780’, May 18, 1965 ( LACM) ; 11 mi NW Lovelock, T25N, R30E, Sect 20, 5000’, Apr 23, 1971 & Jun 23, 1971 ( LACM; RAJC) . Washoe Co.: Gerlach , 4100’, Jun 11, 1971 ( LACM) ; 18 mi S Gerlach , 4500’, Jun 11, 1971 ( RAJC) ; 19 mi S Gerlach , 4500’, Jun 11, 1971 ( RAJC) ; 5 km S Nixon , 1185 m, Jul 7, 2004 ( UCDC) ; T23 N, R21E, Sect 20, 1320 m, Aug 10, 1972 ( LACM) ( Figure 41B ).

Etymology. The specific epithet, pseudolariversi , refers to its close similarity to V. lariversi , as exemplified by numerous series having been misidentified as V. lariversi until differences were conveyed to us by Phil Ward.

Discussion. Veromessor pseudolariversi is broadly sympatric with several congeners including V. smithi , V. lariversi , and V. lobognathus . Veromessor pseudolariversi workers are separated from V. lobognathus and V. smithi by: (1) smaller size (HW = 0.93–1.37 mm), (2) body concolorous light yellowish to yellowish-orange or yellowishred, gaster often slightly darker, (3) maximum basal width of scape less than maximum preapical width, and (4) mandibles with 7 teeth. For V. lobognathus and V. smithi : (1) larger in size (HW = 1.28–1.82 mm), (2) concolorous orangish-brown to rust colored, (3) maximum basal width of scape greater than maximum preapical width, and (4) mandibles with 8 teeth.

Veromessor pseudolariversi is most similar to the closely related V. lariversi , as reflected by the fact that numerous series of V. pseudolariversi were misidentified as V. lariversi . However, these two species display consistent differences in morphology. Morphological differences that separate the two species include that workers of V. pseudolariversi : (1) in profile, anteroventral margin of postpetiole discontinuous with margin interrupted by a minute process, margin concave anterior to process ( Figure 29D ), (2) in dorsal view and in profile, the pronotum with discontinuous to continuous, irregular, transverse rugae; dorsum of mesonotum with one to few weak, irregular, usually discontinuous, longitudinal rugae ( Figure 29E–F ), and (3) a relatively larger eye with more facets ( Figure 30 ). For workers of V. lariversi : (1) in profile, ventral margin of postpetiole continuous, lacking a minute process ( Figure 29A ), (2) in dorsal view and in profile, the pronotum and mesonotum arugose, weakly to strongly coriarious to punctulate-granulate ( Figure 29B–C ), and (3) a relatively smaller eye with fewer facets ( Figure 30 ). Queens and males of the two species also differ in size. Worker allometry is similar for both species, but queens of V. lariversi are distinctly larger than those of V. pseudolariversi , but their males are smaller ( Figure 33 ). A molecular phylogeny that used UCEs shows that specimens that can be identified as V. lariversi and V. pseudolariversi using the above characters form sister but divergent, reciprocally monophyletic lineages, including specimens occurring in sympatry at Fort Churchill State Historic Park in Lyon County, Nevada (M.L. Borowiec, unpub. data).

Biology. As noted in the species account for V. lariversi , the biology of V. lariversi and V. pseudolariversi are probably similar, but it is difficult to ascribe published information to one species or the other because series were not referenced in papers, voucher series were not collected, or series were absent from loans that were examined. The following information on biology includes only that which could be verified from examined series of V. pseudolariversi or field observations.

Veromessor pseudolariversi workers are solitary, nocturnal foragers. Nests are usually polydomous and range from an entrance lacking a tumulus up to tumuli 10–15 cm in diameter (R.A. Johnson, pers. obs.). Colonies reach up to about 1,000 workers, and they are presumably monogynous. Workers are mostly monomorphic. Snelling and George (1979) collected both V. lariversi and V. pseudolariversi in California, and they indicated that colonies appear to aestivate during summer months. It seems more likely that these authors observed inactive colonies given that both RAJ and MLB have observed V. pseudolariversi foraging in June.

Gland chemistry has not been examined in V. pseudolariversi . Like other small-colony congeners, workers of V. pseudolariversi have a small pygidial gland reservoir and lack a textured tergal cuticle ( Hölldobler et al., 2013).

Mating flights have not been observed, but males were collected on June 11 and dealate queens were found on the ground at night and early morning on 29 June–3 July, indicating that mating flights occur during summer, probably during pre-dawn hours. Cole (1963) found two dealate queens in one excavated nest, but it is unclear if this record was for V. lariversi or V. pseudolariversi .

Veromessor pseudolariversi is a mid-elevation species of the Great Basin Desert that occurs at elevations from 1,145 –1,305 m. This species occurs in the Great Basin shrub steppe, Mohave desert, and Western short grasslands ecoregions, as defined by by Olson et al. (2001) ( Figure 41B ).

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 29. Photographs of diagnostic characters to distinguish between workers of Veromessor lariversi Smith and (A–C) V. pseudolariversi (D–F).Photographs of V. lariversi worker (CASENT0923148): (A) anteroventral margin of postpetiole lacking a minute process, margin with a continuous profile, and (B) in profile and (C) in dorsal view, pronotum and mesonotum arugose and weakly to strongly coriarious to punctulate-granulate. Photographs of V. pseudolariversi paratype worker (CASENT0923121): (D) anteroventral margin of postpetiole with a minute process that interrupts the continuous profile, margin weakly concave anterior to process, and (E) in profile and (F) in dorsal view, pronotum with discontinuous to continuous, wavy to irregular transverse rugae; dorsum of mesonotum with one to few weak, wavy to irregular, usually discontinuous longitudinal rugae. Photographs by Michele Esposito and Wade Lee from www.AntWeb.org.

FIGURE 30. Bivariate plots for workers of V. lariversi and V. pseudolariversi: (A) mesosoma length versus number of eye facets, and (B) mesosoma length versus eye length. Sample size for each species is in parentheses.

FIGURE 33. Bivariate plots for workers, queens, and males of Veromessor lariversi and V. pseudolariversi: (A) head width versus head length and (B) head width versus mesosoma length. Sample size for each caste is in parentheses.

FIGURE 41. Geographic distribution of: (A) Veromessor pergandei, (B) V. pseudolariversi, and (C) V. smithi. The larger black circle in panels B & C denotes the type locality.

FIGURE 42. Photograph of Veromessor pseudolariversi holotype worker: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0923119). Photographs by Wade Lee from www.AntWeb.org.

FIGURE 43. Photograph of Veromessor pseudolariversi alate queen: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (LACMENT370281). Photographs by Wade Lee from www.AntWeb.org.

FIGURE 44. Photograph of Veromessor pseudolariversi male: (A) frontal view of head, (B) lateral view of body, and (C) dorsal view of body (CASENT0869851). Photographs by Robert Johnson from www.AntWeb.org.