Camponotus laevigatus

Camponotus laevigatus is an arboreal species (Fisher, 1997) that nests in dead branches of the oak Quercus wislizenii and possibly other species of Quercus where it is probably polygynous (Gadau et al., 1999), and is primarily active at night. It is the dominant ant in many oak communities in California. It feeds on the exudates on the trees, although the nature of the exudates is unknown. Foragers are attracted to honey baits, and collect living insects and bird droppings. (Gadau et al., 1999; Mackay, 2019; Ward & Boudinot, 2021)

Compare with Camponotus americanus, Camponotus herculeanus, Camponotus modoc, Camponotus novaeboracensis, Camponotus schaefferi, Camponotus texanus.

The major worker of C. laevigatus is a predominantly black ant with most surfaces relatively smooth. The cheeks and malar area have numerous erect and suberect setae; the scape is without erect and suberect setae (except at the apex). Appressed pubescence is very sparse, short (> 0.01 mm) and obvious only on the side of the head and the dorsum of the gaster.

The minor worker is black, with dark brown appendages. Most surfaces are at least weakly shining, the side of the head and the side of the gaster are nearly glossy. The clypeus and the cheeks have several erect and suberect setae, erect and suberect setae are lacking on the scape and on the side of the head, there are few erect and suberect setae on the dorsum of the mesosoma, dorsum of the petiole, and all surfaces of the gaster. The head and the gaster have tiny appressed setae.

Comparisons
Major workers could also be confused with those of Camponotus modoc. They always have a few erect setae on the cheeks and malar area, whereas, C. modoc is without these setae.

Camponotus laevigatus is very similar to Camponotus americanus (E USA, Oregon). It can be separated by color (entirely dark or black, C. americanus is in part yellow or brown) and by the western distribution (versus the primarily eastern distribution of C. americanus).

Smith (1953) compared C. laevigatus to Camponotus novaeboracensis (S Canada, US, has not been reported in S CA), but separates it on the basis of color, by the coarse piligerous foveolae on the anterior part of the head and by other [not specified] characters. Camponotus laevigatus can be easily separated from C. novaeboracensis on the basis of color and by the presence of erect and suberect setae on the cheeks and malar area in C. laevigatus (absent in C. novaeboracensis). Smith (1953) noted that C. laevigatus varies considerably in the numbers of erect and suberect setae on the mesosoma and the number and size of the foveolae on the cheeks.

Gadau et al. (1999) suggest that C. laevigatus is not similar to Camponotus herculeanus (S Canada, US), based on the mitochondrial gene cytochrome oxidase I, and perhaps forms a group with Camponotus texanus (W TX) and Camponotus schaefferi (AZ, NM) and is part of the subgenus Camponotus clade. Camponotus laevigatus can be separated from these other two species as it is nearly concolorous black, not medium brown to yellowish-red as in C. schaefferi nor bicolored as in C. texanus. Workers of C. schaefferi usually have a few erect setae along the shaft of the scape, which are also present in majors and minors of Camponotus laevigatus, but absent in C. texanus (except at the apex of the scape), a few tiny setae elevated slightly from the shaft of the scape occur in C. texanus). It did not form a clade with the herculeanus group, based on mitochondrial gene cytochrome oxidase 1 (Gadau et al., 1999).

Camponotus laevigatus has an intermediately developed clypeal notch, which prevents C. texanus (western Texas), C. schaefferi (New Mexico and Arizona) and C. laevigatus from forming a separate species complex, based on morphology.

Camponotus laevigatus is black, not bicolored as in Camponotus bellacolor (NE Mexico).

Camponotus laevigatus is found in oak woodlands (Gadau et al., 1999) and also in Jeffrey pine forests.

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

Biology
The Argentine ant, Linepithema humile, has a negative impact on C. laevigatus in northern California riparian woodlands (Holway, 1998). It is the host of Wolbachia bacteria (Wernegreen et al., 2009).

Nomenclature

 * . Formica laevigata Smith, F. 1858b: 55 (w.q.) U.S.A. (California).
 * [Misspelled as levigatus by Roger, 1863b: 5, Dalla Torre, 1893: 238, and others; misspelled as laevitatus by Borgmeier, 1927c: 149.]
 * Wheeler, W.M. 1910d: 327 (s.m.); Wheeler, G.C. & Wheeler, J. 1968: 216 (l.).
 * Combination in Camponotus: Roger, 1863b: 5;
 * combination in C. (Camponotus): Forel, 1914a: 266.
 * Status as species: Mayr, 1863: 416; Roger, 1863b: 5; Mayr, 1886c: 356; Mayr, 1886d: 420; Cresson, 1887: 255; Dalla Torre, 1893: 238; Emery, 1893i: 671; Emery, 1896d: 372 (in list); Wheeler, W.M. 1910d: 327 (redescription); Wheeler, W.M. 1910g: 571; Forel, 1914a: 266; Wheeler, W.M. 1917a: 556; Emery, 1925b: 75; Essig, 1926: 868; Cole, 1936a: 39; Cole, 1942: 388; Creighton, 1950a: 369; Smith, M.R. 1951a: 840; Cole, 1954f: 272; Smith, M.R. 1967: 366; Hunt & Snelling, 1975: 22; Yensen, et al. 1977: 184; Wheeler, G.C. & Wheeler, J. 1978: 392; Smith, D.R. 1979: 1426; Allred, 1982: 455; Wheeler, G.C. & Wheeler, J. 1986g: 60; Mackay, Lowrie, et al. 1988: 106; Blacker, 1992: 9; Bolton, 1995b: 107; Mackay & Mackay, 2002: 293; Hansen & Klotz, 2005: 83; Ward, 2005: 63; Mackay, 2019: 241 (redescription).
 * [Note: Mackay, 2019: 241, records that “most of these (earlier) references are probably misidentifications of C. laevissimus”.]
 * quercicola. Camponotus (Camponotus) quercicola Smith, M.R. 1954b: 211 (w.) U.S.A. (California).
 * Gadau, et al. 1999: 516 (q.m.)
 * Status as species: Smith, M.R. 1958c: 143; Smith, D.R. 1979: 1427; Wheeler, G.C. & Wheeler, J. 1986g: 60 (in key); Bolton, 1995b: 119; Gadau, et al. 1999: 514 (redescription); Ward, 2005: 63; Mackay, 2019: 320 (redescription).
 * Junior synonym of laevigatus: Ward & Boudinot, 2021: 46.

Taxonomic Notes
Mackay (2019) discovered that the types of this species do not match the common shiny, glossy specimens that have been referred to as C. laevigatus for over 160 years. He proposed that this common, shiny species is actually a separate species, which he named Camponotus laevissimus. Most literature (probably except for the original description) as well as specimens in museums labelled as C. laevigatus actually refer to C. laevissimus.

Ward & Boudinot (2021) found that true Camponotus laevigatus is a shiny black species, with relatively sparse standing pilosity, inconspicuous pubescence, slender scape base, and ecarinate clypeus. Examination of the lectotype image shows that Camponotus laevigatus is conspeciﬁc with Camponotus quercicola, a widespread California species that nests in the trunks and branches of oak trees (Gadau et al. 1999). Mackay (2019) claimed that C. laevigatus differs from C. quercicola in having reduced pilosity on the head, but the lectotype is an old specimen in which the hairs are evidently abraded. Note the asymmetry in presence of hairs on the two sides of the head in the AntWeb image (e.g., short setae present on the left malar region but not on the right side). Moreover, the amount of standing pilosity shows considerable variation in workers of C. quercicola, including setation on the malar region (Smith 1954; Gadau et al. 1999). We have examined a large series of C. quercicola from throughout California, and we find that the type of C. laevigatus falls easily within the range of variation exhibited by this species.

Description
Major worker measurements (mm): HL 3.16 - 3.30, HW 3.12 - 3.20, SL 2.92, EL 0.73 - 0.74, CL 1.08 - 1.15, CW 1.26 - 1.30, WL 4.20 - 4.36, FFL 2.60 - 2.66, FFW 0.84 - 0.90. Indices: CI 97 - 99, SI 88 - 92, CLI 113 - 117, FFI 32 - 34.

Mandible with 5 teeth; anterior border of clypeus concave, crenulated with small lateral teeth or angles; head narrowed anteriorly, sides of head convex, posterior margin concave; eyes failing to reach sides of head by about ½ minimum diameter; scape extending 2 funicular segments past posterior lateral corner of head; propodeum angulate between 2 faces of equal length, spiracle elongate; petiole narrow in profile, apex convex as seen from front.

Erect and suberect setae sparse, present on clypeus, including disc, on cheeks, on area along frontal carinae, near posterior margin of head, ventral surface of head, few setae on mesosoma, except present on angle between 2 faces of propodeum, present on petiole and gaster, absent on sides of head near eyes, on posterior lateral corners of head, scapes (except at apex), absent on tibiae, except for 1 - 2 rows of bristles on flexor surface of distal third of posterior tibia.

Head densely punctate, with scattered larger punctures, posterior half of head coriaceous, mesosoma coriaceous, gaster finely transversely striolate, most surfaces at least weakly shining, side of head strongly shining dorsum of gaster strongly shining.

Concolorous black.

Minor worker measurements (mm): HL 2.64 - 2.66, HW 1.92 - 2.30, SL 2.68, EL 0.64 - 0.65, CL 0.85 - 0.86, CW 1.08 - 1.10, WL 3.76 - 3.86, FFL 2.40 - 2.44, FFW 0.78. Indices: CI 73 - 86, SI 101 - 102, CLI 125 - 129, FFI 32.

Minor worker similar to major worker, except head elongate, sides of head nearly straight, almost parallel, posterior margin straight, eyes failing to reach sides of head by about ¼ minimum diameter; scapes extending 2 - 3 funicular segments past posterior lateral corner of head; propodeum angulate between 2 faces of equal length, posteropropodeum concave.

Pilosity, sculpture and color as in major worker.

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Des Lauriers J., and D. Ikeda. 2017. The ants (Hymenoptera: Formicidae) of the San Gabriel Mountains of Southern California, USA with an annotated list. In: Reynolds R. E. (Ed.) Desert Studies Symposium. California State University Desert Studies Consortium, 342 pp. Pages 264-277.
 * Gadau J., Brady S. G. and Ward P. S. 1999. Systematics, distribution and ecology of an endemic California Camponotus quercicola (Hymenoptera: Formicidae). Annals of the Entomological Society of America 92: 514-522
 * Holway D.A. 1998. Effect of Argentine ant invasions on ground-dwelling arthropods in northern California riparian woodlands. Oecologia. 116: 252-258
 * Johnson, R.A. and P.S. Ward. 2002. Biogeography and endemism of ants (Hymenoptera: Formicidae) in Baja California, Mexico: a first overview. Journal of Biogeography 29:10091026/
 * Longino, J.T. 2010. Personal Communication. Longino Collection Database
 * Smith M. R. 1954. A new Camponotus in California apparently inhabiting live oak, Quercus sp. (Hymenoptera, Formicidae). Journal of the New York Entomological Society 61: 211-214.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Ward P. S. 2005. A synoptic review of the ants of California (Hymenoptera: Formicidae). Zootaxa 936: 1-68.