Veromessor pseudolariversi

Veromessor pseudolariversi
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Stenammini
Genus:	Veromessor
Species:	V. pseudolariversi
Binomial name
Veromessor pseudolariversi Johnson, Borowiec, Snelling & Cole, 2022

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 Veromessor 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.

Photo Gallery

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  Johnson et al., 2022, Fig. 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.

Identification

Worker

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
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)

Queen

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
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)

Male

This caste is diagnosed by the following combination of features:

1. dark brownish-black
2. medial lobe of clypeus with several irregular longitudinal rugae with prominent medial carina that bifurcates near anterior margin
3. preapical tooth small; mandibles with 1–2 minute teeth basad of preapical tooth
4. in frontal view, anterior ocellus slightly above level of top of eyes
5. 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
6. propodeum with moderately strong rugae, interrugae moderately coriarious; propodeal spines consist of denticles
7. metasternal process elongate, digitiform
8. 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)

Discussion

Veromessor pseudolariversi is broadly sympatric with several congeners including Veromessor smithi, Veromessor lariversi and Veromessor 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 yellowish red, gaster often slightly darker
3. maximum basal width of scape less than maximum preapical width
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
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)
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)
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).

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  Johnson et al., 2022, Fig. 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.
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  Johnson et al., 2022, Fig. 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.
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  Johnson et al., 2022, Fig. 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.
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  Johnson et al., 2022, Fig. 55. Bivariate plots for workers showing head width versus head length (left panels) and mesosoma length versus pronotum width (right panels) for ecologically similar pairs of small colony species of Veromessor: V. lariversi and V. pseudolariversi (A–B), V. lobognathus and V. smithi (C–D), V. chicoensis and V. stoddardi (E–F). Note that the x-axis scale is the same for all panels on the left and for all panels on the right so that sizes can be compared directly across species groups. Sample size for each species is given in parentheses.
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  Johnson et al., 2022, Fig. 53. Eye area (mm2) (A), facet number (B), and mean facet diameter (μm) (C) for pale and dark colored species of Veromessor. Two species are pale (V. lariversi, V. pseudolariversi—open symbols and regular font), while the other eight species are dark (filled symbols and bold font). For each species, number of workers examined and number of colonies they were derived from is given in parentheses. Significant differences (P < 0.05) among species are denoted after each species name by the letters a–g: a > b > c > d > e > f > g; the three sets of letters for each species correspond to panels A, B, and C, respectively. Groupings are based on univariate F tests within MANCOVA followed by pairwise comparisons using a least significant differences test (see also Johnson & Rutowki, 2022).
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  Johnson et al., 2022, Fig. 56. Queen body size across species of Veromessor based on average head width, average head length, and average mesosoma length. Species are ordered (left to right) from shortest to longest mesosoma length.

Keys including this Species

• Key to Veromessor species

Distribution

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  Johnson et al., 2022, Fig. 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.

Latitudinal Distribution Pattern

Latitudinal Range: 41° to 36.5°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: Johnson et al., 2022

Distribution based on Regional Taxon Lists

Nearctic Region: United States (type locality).

Distribution based on AntMaps

Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.

Biology

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.

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).

Castes

Queen

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  Johnson et al., 2022, Fig. 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.

Male

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  Johnson et al., 2022, Fig. 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.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

• pseudolariversi. Veromessor pseudolariversi Johnson, Borowiec, Snelling & Cole, 2022: 80, figs 1H, 29D–F, 41B, 42–44 (w.q.m.) UNITED STATES (Nevada).

Type Material

• Holotype worker [USNM: CASENT0923119]: UNITED STATES, Nevada: Nye County, 7 mi SSE Beatty, 36o49’N 116o44’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).

References

• Johnson, R.A., Borowiec, M.L., Snelling, R.R., Cole, A.C. 2022. A taxonomic revision and a review of the biology of the North American seed-harvester ant genus Veromessor (Hymenoptera: Formicidae: Myrmicinae). Zootaxa 52061, 1-115 (doi:10.11646/zootaxa.5206.1.1).