Camponotus laevissimus

Camponotus laevigatus is less common than other forest dwelling North American carpenter ants that have both large colonies and large soldiers. The size of mature colonies is uncertain. A single nest collected in Washington state was estimated to contain about 1,000 individuals but Akre et al. (1994) speculated that colonies may contain ten to twenty times as many workers. Individuals forage during the day and do not use regular trails (Hansen and Akre 1985).

Mackay (2019) was surprised to discover that the types of Camponotus laevigatus do not correspond to the specimens that have been identified as C. laevigatus for over 160 years, making it necessary to create a new name, C. laevissimus, for this common species. Probably all literature citations (other than the original description) and specimens in museums labelled as C. laevigatus are actually C. laevissimus. Unfortunately, Mackay (2019) labelled the specimens as C. laevigatus and returned them to the museums before he realized the correct identity of C. laevigatus. He has not seen other specimens of C. laevigatus besides the type series in The Natural History Museum (London).

Compare with Camponotus laevigatus, Camponotus schaefferi, Camponotus texanus.

Camponotus laevissimus is easily separated from all other North American species, as it is the only one in which the majors, minors, females and males are shiny black and have short, bristly setae on the antennal scapes.

Comparisons
The erect and suberect setae on the scapes of all castes of C. laevissimus may cause confusion with Camponotus schaefferi (Arizona and New Mexico), which also has erect and suberect setae on the scapes and is glossy and shiny. It can be easily separated as C. laevissimus is black and C. schaefferi is yellowish brown. Occasionally the scape of the shiny Camponotus texanus (western Texas) has a few erect setae. Camponotus laevissimus can be easily separated on the basis of color, as C. texanus is bicolored with the head and gaster black and the mesosoma red.

Camponotus laevissimus is a high elevation ant, mostly occurring at elevations of between 2000-2500 meters. It is found in ponderosa pine forests, oak forests, in sparse Robinia understory on a north facing slope and in pine/spruce/aspen forest. It is also found in mixed pine, deciduous forest, pine/oak riparian forests, pinyon juniper woodlands, pine/fir/oak transition, pine/spruce/fir forest and pine mixed with deciduous forest. It is occasionally found in urban habitats (Mackay and Mackay, 2002). Palladini et al. (2007) found it in temperate coniferous forests, often in younger stands.

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

Camponotus laevissimus occurs in forests where it nests in rotten logs and stumps (Mackay and Mackay, 2002). Nests are often found in hard, recently cut stumps or logs, but it is also found in rotten log with loose bark. Young nests are usually found under the bark of logs and stumps. It forms large colonies (Wheeler, 1910a).

Wheeler (1917c: 556) reported it nesting in huge stumps near sea level at Seattle, but it is distinctly boreal further south, rarely occurring at elevations below 1333-1667m (4000-5000 feet) and occurring as high as 3667m (11,000 feet) on Alta Peak in California.

We observed the excavation of a solid pine stump by C. laevissimus that had been recently cut (probably within a year). The workers inside the nest would come to the surface with pieces of wood, which they would drop near the entrance hole, then return to excavating. A second set of workers would take the wood fragments and dump them over the side of the stump.

Brood and sexuals were found in nests from April - October. Founding queens were found from June - August.

Camponotus laevissimus is primarily diurnal (Hansen and Klotz 2005; Palladini et al., 2007), a very active ant foraging in the afternoon and sucking liquids (Paul and Roces, 2003). It is one of the abundant native species which does not visit the extrafloral nectaries of the barrel cactus Ferocactus wislizeni (Ness et al., 2009). They prey on the western spruce budworm pest, Choristoneura occidentalis (Lepidoptera: Tortricidae) (Youngs and Campbell, 1984).

Reemer (2012) discusses the parasitism by the syrphid fly Microdon sp., and Akre et al., (1988) discuss parasitism by M. piperi. It is infected by the hymenopterous parasite Pseudochalcura gibbosa (Eucharitidae) (Heraty, 1986; Lachaud, J.-P. and G. Pérez-Lachaud. 2012). They are the host of the endosymbiotic bacterium Candidatus Blochmannia (as C. laevigatus, Degnan et al., 2004), as well as Wolbachia bacteria (as C. laevigatus, Wernegreen et al., 2009).

Camponotus laevissimus is the prey of the harvester ant Pogonomyrmex montanus (probably found dead) and was found in a Bufo boreus toad stomach.

Camponotus laevissimus is able to colonize recently created stumps and logs. Some of the workers excavate small pieces of wood inside the stump and deposit the pieces near the entrance hole. Other workers pick up the pieces and carry them to the edge of the stump and drop them (Mackay and Mackay, pers. obs.).

Nests of C. laevissimus are invaded and displaced by the ant Formica ravida (Mackay and Mackay, 1982). When a nest is attacked by F. ravida, carpenter ant workers retreat to the innermost tunnels of the stump, where they are slowly killed by the invading colony, which uses the tunnels excavated by Camponotus.

Ramón and Gronenberg (2005) include labeled dissections of the head and brain. Paul and Groenberg (2002) discuss the neuroanatomy involved with the mandibule closer muscle. Workers have broad-spectrum sensitivity, allowing these ants to detect cuticular hydrocarbons from both nestmates and non-nestmates (Sharma et al., 2015).

The live body mass is 64 mg and the standard metabolic rate is higher than other species studied (Lighton and Wehner, 1993).

It is an occasional pest in buildings (Mackay and Mackay, 2002), but is rarely a structural pest (Hansen and Klotz, 2005).

Older Literature
Wheeler (1910) - C. laevigatus is a mountain ant peculiar to the high ranges of the western states. It extends into Mexico and also for a short distance into British America (Vancouver Island, according to Lord). I believe that it will rarely be found below an altitude of 6000 ft. I have seen it only at elevations of 7000-8000 ft. in the mountains of Colorado. It forms large colonies which nest in dry stumps or logs after the manner of Camponotus herculeanus and its various subspecies and varieties. In behavior it closely resembles the south European Camponotus vagus.

Gregg (1963) reports from Colorado: "..this species is closely associated with wooded and forested areas and forest margins, not being found at any great distances from them in open habitats. It requires rotting logs in various degrees of decomposition, especially the early stages, although if more records were available the ant might be seen to utilize a greater assortment of decaying woods. My general impression is that laevigatus shows a preference for rather sound pine logs in the second to third stages of disintegration."

Mackay and Mackay (2002) - Deciduous forests, oak forests (Gamble), pinyon-juniper, fir and pine forests at higher elevations or latitudes, 2130 - 2447 meters in elevation. Nests are occasionally found in urban areas. Camponotus laevigatus is a forest species that nests in rotten logs and stumps. It is an occasional pest in buildings.Brood was found in nests in August, new nests were established in August. They are prey of Pogonomyrmex montanus in southern California.

Nevada, Wheeler and Wheeler (1986) - We have 11 records from 11 localities, which are widely scattered throughout the state, except none in the northwest; 4,600-8,600 ft. Five records were from the Coniferous Forest Biome and 1 from Pinyon-Juniper. Two were reported nesting in prostrate coniferous trunks and 1 was in the wood of an abandoned mine building.

Nomenclature

 * . Camponotus (Camponotus) laevissimus Mackay, 2019: 247, figs. 189, 241-244, pls 21-24 (s.w.q.m.) U.S.A. (California, Arizona, Colorado, Idaho, Montana, New Mexico, Nevada, Oregon, South Dakota, Utah, Washington), CANADA (Alberta, British Colombia), MEXICO (Baja California, Tamaulipas).

Major worker measurements (mm): HL 2.54 - 3.22, HW 2.82 - 3.66, SL 2.48 - 3.16, EL 0.58 - 0.64, CL 0.95 - 1.26, CW 1.23 - 1.45, WL 3.80 - 4.46, FFL 2.26 - 2.66, FFW 0.73 - 0.93. Indices: CI 111 - 114, SI 98, CLI 115 - 129, FFI 32 - 35.

Mandible with 5 teeth; anterior border of clypeus slightly concave; head narrowed anteriorly, posterior margin nearly straight; eyes failing to reach sides of head by about ½ minimum diameter; scape extending 1 - 2 funicular segments past posterior lateral corner of head; propodeum weakly angulate between faces, dorsopropodeum slightly longer than posteropropodeum, spiracle elongate; petiole narrow as seen in profile, apex convex as seen from front.

Erect and suberect setae fine, white, abundant on most surfaces, including clypeus (distributed across disc), cheeks, malar area, sides of head, along frontal carinae extending posteriorly to posterior margin, posterior lateral corners of head, setae on scapes fine, erect, bristly, abundant on most other surfaces, including legs (and tibiae), petiole and gaster; appressed pubescence very sparse, few setae on head, dorsum of mesosoma and dorsum of gaster.

All surfaces smooth, glossy, shiny.

Concolorous black.

Minor worker measurements (mm): HL 1.84 - 2.38, HW 1.68 - 2.32, SL 2.02 - 2.44, EL 0.44 - 0.50, CL 0.55 - 0.75, CW 0.89 - 1.11, WL 2.78 - 3.44, FFL 1.76 - 2.24, FFW 0.49 - 0.65. Indices: CI 91 - 97, SI 103 - 110, CLI 148 - 161, FFI 28 - 29.

Similar to major worker, except head oval-shaped, scape extending nearly ½ length past posterior lateral corner of head, pilosity, sculpture and color as in major worker.

Female measurements (mm): HL 2.84 - 3.06, HW 3.12 - 3.16, SL 2.44 - 2.56, EL 0.70 - 0.76, CL 1.01 - 1.11, CW 1.29 - 1.33, WL 5.42 - 5.60, FFL 2.55 - 2.57, FFW 0.73 - 0.79. Indices: CI 102 - 111, SI 84 - 86, CLI 119 - 127, FFI 28 - 31.

Similar to major worker, head shape similar, scape extends 1-2 funicular segments past posterior lateral corner of head, pilosity, sculpture and color as in major worker.

Male measurements (mm): HL 1.66 - 1.78, HW 1.62 - 1.74, SL 1.88 - 1.92, EL 0.55 - 0.60, CL 0.48 - 0.49, CW 0.78 - 0.84, WL 3.80 - 4.04, FFL 2.34 - 2.36, FFW 0.50 - 0.53. Indices: CI 97 - 99, SI 108 - 113, CLI 163 - 172, FFI 21 - 22.

Large, black specimen, which is similar to the major worker in many aspects, including the pilosity and color, but weakly shining.

References based on Global Ant Biodiversity Informatics

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