Introduction
Camponotus Mayr, 1861 (Formicinae: Camponotini) is a globally widespread genus of polymorphic ants, readily recognized by a single-segmented petiole and a terminal acidopore. More than 900 species are described worldwide, with approximately 50 recorded from the United States; diversity is highest in the eastern and southeastern regions (Bolton 1995; Smith 1979; Deyrup 2003).
Camponotus americanus Mayr, 1862 belongs to the nominotypical subgenus Camponotus, which comprises the true carpenter ants that typicallynest in wood. Species of this subgenus are medium to large in size and moderately polymorphic, and are characterized by an ecarinate to weakly carinate clypeus, antennal scapes not flattened basally, and well-developed clypeal fossae; major workers usually have heads broader than long. In full-face view, the posterior margin of the head is broadly rounded and never truncate. Mandibles bear four to five teeth. In profile, the mesosoma is evenly arched, with a broadly rounded propodeum. Coloration is generally contrasting, with the mesosoma lighter than the head and gaster. Four species of the subgenus Camponotus are currently known from Mississippi.
Taxonomic history
Camponotus americanus Mayr, 1862: 661 (w.q.) U.S.A. (Louisiana). Nearctic.
Primary type information: Primary type material: 1 (?) syntype worker, 1 (?) syntype queen. Primary type locality: U.S.A.: New Orleans (no collector’s name). Primary type depository: NHMW. Type notes: No indication of number of specimens is given.
Combination in Camponotus (Camponotus): Emery, 1925d: 74. Junior synonym of Campontus castaneus: Mayr, 1886d: 420; Cresson, 1887: 255; Dalla Torre, 1893: 223. Subspecies of Camponotus castaneus: Emery, 1893k: 674; Emery, 1895d: 336; Emery, 1896j: 372 (in list); Forel, 1904c: 381; Wheeler, 1905j: 402; Wheeler, 1906g: 22; Wheeler, 1910g: 323 (redescription); Wheeler, 1910a: 571; Wheeler, 1913d: 117; Wheeler, 1916r: 600; Wheeler, 1917k: 465; Emery, 1925d: 74; Smith, 1930a: 6; Wheeler, 1932a: 13; Dennis, 1938: 300; Wesson & Wesson, 1940: 103; Buren, 1944a: 294; Smith, 1951c: 839.
Status as species: Roger, 1863b: 5; Mayr, 1863a: 398; Creighton, 1950a: 365; Eisner & Wilson, 1952: 47; Smith, 1958c: 142; Carter, 1962a: 7 (in list); Smith, 1967a: 366; Smith, 1979: 1425; DuBois & LaBerge, 1988: 145; Deyrup et al., 1989: 100; Wheeler et al., 1994: 305; Bolton, 1995b: 85; Coovert, 2005: 163; Hansen & Klotz, 2005: 81; MacGown & Forster, 2005: 65; MacGown et al., 2007: 10; Ellison et al., 2012: 117; Deyrup, 2017: 186; Mackay, t365; Smith, 1958c: 142; Smith, 1979: 1425; Bolton, 1995b: 85; Mackay, 2019: 163.
Senior synonym of Camponotus rufinasis: Creighton, 1950a: 365; Smith, 1958c: 142; Smith, 1979: 1425; Bolton, 1995b: 85; Mackay, 2019: 163.
Diagnosis
Camponotus americanus could be easily confused with C. castaneus (Latreille), a similarly colored and sized carpenter ant that invades houses and other buildings with more regularity (although not commonly). It can be distinguished from C. castaneus by its darker head and erect hairs on the cheeks. In C. castaneus the head is the same orangish-red color as the rest of the body, and the cheeks (especially as seen in the major workers) lack erect hairs. Southeastern specimens often have spots of darker coloration on the dorsum of the mesosoma on C. americanus, whereas in C. castaneus, the coloration is much more uniform without any mottling or spots of other colors.
Identification
Descriptions for each caste are based on examination of MEM specimens.
Minor worker. TL: 7.52–8.36 mm; HL: 1.86–2.08 mm; HW: 1.34–1.54 mm; SL: 2.46–2.60 mm; ML: 2.94–3.36 mm; EL: 0.48–0.54 mm (n=5, MEM specimens).
Head in full-face view longer than broad; lateral margins anterior to eyes subparallel, posterior to eyes weakly convex and converging toward a broadly rounded occipital margin. Eyes large and strongly convex, not breaking lateral cephalic margin. Frontal carinae short, posteriorly parallel. Clypeus weakly carinate to ecarinate; anteromedian margin broadly convex to nearly straight, not projecting. Mandibles triangular; masticatory margin with five teeth. Antennal scape long, not basally flattened, surpassing occipital margin by ca. 0.5× scape length, lacking erect hairs.
Mesosoma robust; dorsal outline evenly arched, pronotum straight to weakly convex; mesonotum–propodeum continuous. Dorsal face of propodeum weakly concave medially, meeting declivity in a distinct angle. Petiole nodiform; node higher than long, anterior and posterior faces subvertical.
Pilosity sparse and discrete. Vertex and frontal area each bearing a paired series of erect setae; genae with numerous erect setae. Mesosoma with 6–8 pairs of erect setae on pronotum, three pairs on mesonotum, and 2–3 pairs adjacent to propodeal angles. Antennal scapes lacking erect setae. Gastric pubescence extremely sparse, fine, and tightly appressed.
Integument smooth and glossy throughout, with only very fine, superficial microsculpture. Coloration variable: head dark reddish brown to black, with clypeus distinctly paler; mesosoma brownish yellow to yellowish brown, occasionally dorsally infuscate; gaster yellowish brown, sometimes darkened apically; legs pale basally, gradually darkening distally.
Major worker. TL: 10.74 –11.36 mm; HL: 3.06 –3.62 mm; HW: 3.1 –3.76 mm; SL: 2.8 –3.12 mm; ML: 3.98 –4.42 mm; EL: 0.64 –0.68 mm (n=5, MEM specimens).
Head subquadrate in full-face view; lateral margins weakly convex to subparallel; occipital margin straight. Eyes moderately large, weakly flattened, situated posterior to midlength of head. Frontal carinae lyrate. Clypeus ecarinate; anterior margin straight, not projecting. Mandibles triangular; masticatory margin with five teeth. Antennae with scape elongate, tubular, not basally flattened, gradually thickening apically, surpassing the occipital margin by about one-quarter of its length; scapes lacking erect setae.
Mesosoma robust in profile; dorsal outline evenly and continuously arched. Propodeum with obtusely angulate juncture between dorsal and declivitous faces; dorsal face approximately twice as long as the declivity. Petiole nodiform, similar in form to that of minor worker.
Sculpture. Mandibles opaque, coarsely striate-punctate; mandibular teeth smooth and shining. Head capsule opaque, finely and densely punctate.
Pilosity. Setae more abundant than in minor workers: vertex and frontal area with two longitudinal rows of suberect setae; cheeks with numerous erect setae; pronotum with 9–13 pairs of erect setae; mesonotum with 4–8 pairs; propodeal angles with 3–4 pairs. Gastral pubescence extremely sparse, as in minor workers. Color as in minor worker.
Queen. TL: 12.82 –14.72 mm; HL: 3.12 –3.38 mm; HW: 3.12 –3.34 mm; SL: 2.54 –2.9 mm; ML: 4.96 –5.66 mm; EL: 0.72 –0.76 mm (n=5, MEM specimens).
Head broadened posteriorly in full-face view; lateral margins straight to weakly convex, tapering anteriorly; occipital margin straight. Eyes large and strongly convex, positioned posterior to head midlength; ocelli well developed. Frontal carinae, clypeus, and mandibles as in major worker: clypeus distinctly carinate, anterior margin straight and not projecting; mandibles triangular with five teeth. Antennae 12-segmented; scape elongate, surpassing occipital margin by ca. one-third its length, basally flattened and apically expanded.
Mesosoma robust and fully developed for flight. Pronotum nearly vertical, continuous with dorsally flattened mesoscutum; mesoscutellum smoothly convex and clearly elevated above propodeal dorsum. Propodeum rounded; dorsal face shorter than declivity, the latter approximately twice as long. Petiole compressed anteroposteriorly; node with sharp dorsal margins, weakly emarginate medially.
Sculpture: head finely foveolate; pronotum, propodeum, petiole, and gaster finely imbricate; mesoscutum and mesoscutellum smooth and glossy.
Pilosity of suberect golden setae on vertex, occiput, promesonotal suture, mesosoma dorsum, petiolar margin, and gaster; pronotal dorsum lacking erect setae, with standing hairs along the declivity.
Coloration similar to workers: head reddish brown; mandibles, anterolateral clypeal corners, and scape dark brown; mesosoma, petiole, legs, and basal portions of first gastral tergite and sternite yellowish brown.
Male. TL: 8.82 –9.74 mm; HL: 1.52 –1.76 mm; HW: 1.31 –1.52 mm; SL: 1.96 –2.2 mm; ML: 3.8 –4.08 mm; EL: 0.56 –0.60 mm (n=5, MEM specimens).
Head distinctly longer than broad in full-face view; anterolateral margins anterior to eyes subparallel to weakly concave; occipital margin broadly and evenly convex. Eyes very large and strongly protruding, distinctly interrupting lateral cephalic outline. Ocelli moderately large; median ocellus well separated from line connecting posterior margins of compound eyes; lateral ocelli situated at approximately midlength of postocular distance. Frontal carinae short, straight, not reaching postocular margin. Clypeus not produced; anterior margin straight to weakly convex. Mandibles reduced, with a single acute apical tooth. Antennae 13-segmented; scape elongate, surpassing occipital margin by ca. one-half its length.
Mesosoma robust in profile. Pronotum nearly vertical; mesoscutum steeply vertical anteriorly, rounding onto a relatively flat dorsal disc; mesoscutellum gently convex. Propodeum with dorsal face ca. one-half length of declivity; juncture between faces broadly rounded. Petiole nodiform and low, apex rounded.
Integument finely and densely imbricate throughout. Color similar to workers but often lighter, appearing brown to testaceous.
Pilosity sparse and fine: clypeus with 2–3 pairs of setae; frontal area with 1–2 setae; four pairs between ocelli; mesoscutum with four pairs; mesoscutellum with two pairs on disc and four on posterior slope; propodeal declivity with scattered setae; petiole with three pairs at each posterolateral corner; gaster with sparse, fine, filiform setae.
Wings. Forewing with well-developed pterostigma; Sc+R fused; radial sector (Rs) reaching costal margin; M+Cu present; veins 1m–cu, 2rs–m, and Rs+M absent; anal vein (A) longer than M+Cu. Hind wing with fused R+Rs; M+Cu present; cu–a present; anal vein longer than M+Cu.
Biology and economic importance
Camponotus americanus is a common and widespread carpenter ant in the southeastern United States, occurring in diverse habitats including hardwood and pine forests, sandhills, flatwoods, cedar glades, and suburban woodlots. Colonies nest primarily in soil beneath stones, litter, or decayed logs, and secondarily in rotting wood. The species is frequently collected in pitfall traps, litter samples, Lindgren funnels, and light traps, indicating strong surface activity and broad foraging behavior. Ecologically, it functions as a predator and scavenger and contributes to wood decay and nutrient cycling. Although it may occasionally occupy moisture-damaged structural wood, C. americanus is not considered an economically significant pest. Alate flights in the Southeast occur mainly from mid-March through late May.
Pest Status
Because Camponotus americanus nests in rotting logs, it can also be a structural pest, though it is not often reported as such. This ant does not sting but can bite and cause minor irritation by ejecting formic acid from the acidopore located at the posterior portion of the ant.
Distribution
Eastern United States from New England south to Florida and west to Oklahoma and Texas. Reported from all of the southeastern states except Florida: Alabama, Arkansas, Georgia, Louisiana, Missouri, Mississippi, North Carolina, South Carolina, and Tennessee.
Literature Cited
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