Subfamily FORMICINAE Author: Nicole Rasoamanana and Joe A. MacGown |
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 Camponotus castaneus, full face view of minor worker (MS, Pearl River Co.) (Photo by Joe A. MacGown). |
 Camponotus castaneus, lateral view of minor worker (MS, Pearl River Co.) (Photo by Joe A. MacGown). |
 Camponotus castaneus, dorsal view of minor worker (MS, Pearl River Co.) (Photo by Joe A. MacGown). |
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 Camponotus castaneus, full face view of a queen (AL, Bibb Co.) (Photo by Joe A. MacGown). |
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 Camponotus castaneus, dorsal view of a queen (AL, Bibb Co.) (Photo by Joe A. MacGown). |
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 Camponotus castaneus, full face view of a male (MS, Oktibbeha Co.) (Photo by Joe A. MacGown). |
 Camponotus castaneus, lateral view of a male (MS, Oktibbeha Co.) (Photo by Joe A. MacGown). |
 Camponotus castaneus, dorsal view of a male (MS, Oktibbeha Co.) (Photo by Joe A. MacGown). |
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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).
Taxonomic history
Camponotus castaneus (Latreille, 1802) valid
Formica castanea Latreille, 1802a: 118, pl. 3, figs. 11, 12 (w.q.m.) U.S.A. (Carolina, Pennsylvania). Nearctic.
Primary type information: Primary type material: syntype worker(s), syntype queen(s), syntype male(s) (numbers not stated). Primary type localities: U.S.A.: Carolina (Bosc), U.S.A.: Pennsylvania (Beauvois). Primary type depository: MNHN (possibly also MRSN).
Combination in Camponotus: Roger, 1863b: 6; in Camponotus (Tanaemyrmex): Creighton, 1950a: 375; in Camponotus (Camponotus): Forel, 1914a: 266; Mackay, 2019: 182. Junior synonym of Camponotus herculeanus: Smith, 1858a: 53; Mayr, 1863a: 399; Forel, 1874: 96 (in list); Emery & Forel, 1879: 447. Status as species: Lepeletier de Saint-Fargeau, 1835: 215 (redescription); Haliday, 1836: 329; Mayr, 1886d: 420; Forel, 1886h: 141; Cresson, 1887: 255; Dalla Torre, 1893: 223; Emery, 1893k: 673; Emery, 1896j: 372 (in list); Wheeler, 1905j: 402; Wheeler, 1906g: 22; Wheeler, 1910g: 321 (redescription); Wheeler, 1910a: 571; Wheeler, 1913d: 117; Forel, 1914a: 266; Forel, 1914d: 288; 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; Creighton, 1950a: 375; Smith, 1951c: 839; Smith, 1958c: 143; Carter, 1962a: 7 (in list); Smith, 1979: 1428; DuBois & LaBerge, 1988: 147; Deyrup et al., 1989: 100; Bolton, 1995b: 91; Deyrup, 2003: 44; Coovert, 2005: 164; Hansen & Klotz, 2005: 95; MacGown & Forster, 2005: 65; MacGown et al., 2007: 19; Ellison et al., 2012: 119; Deyrup, 2017: 187; Mackay, 2019: 182 (redescription).
Senior synonym of Camponotus clarus Mayr, 1862: 660; Mayr, 1886d: 420; Forel, 1886h: 141; Cresson, 1887: 255; Dalla Torre, 1893: 223; Emery, 1896j: 372; Smith, 1951c: 839; Smith, 1979: 1428; Bolton, 1995b: 91; Mackay, 2019: 182.
Senior synonym of Camponotus melleus: Mayr, 1886d: 420; Forel, 1886h: 141; Cresson, 1887: 255; Dalla Torre, 1893: 223; Emery, 1896j: 372; Wheeler, 1906g: 22; Wheeler, 1910g: 321; Emery, 1925d: 74; Creighton, 1950a: 375; Smith, 1951c: 839; Smith, 1979: 1428; Bolton, 1995b: 91; Mackay, 2019: 182.
Diagnosis
Camponotus castaneus is a medium–large, moderately polymorphic species of the subgenus Camponotus, readily recognized by its uniformly castaneous to yellowish-brown coloration and combination of head, mesosoma, and pilosity characters. Workers exhibit weak cephalic allometry: majors with subquadrate heads and a shallowly concave occipital margin; minors with heads longer than broad and a broadly rounded posterior margin. The clypeus is evenly convex, ecarinate to weakly carinate, with the anterior margin broadly rounded and not projecting beyond the mandibular bases. Antennal scapes are long and terete, surpassing the posterior head margin by approximately one-half their length in minors and one-third in majors. Mesosoma low and evenly arched in profile; propodeum rounded, without a distinct angular transition between dorsal and declivitous faces. Petiole thick and nodiform in workers, becoming strongly anteroposteriorly compressed in queens. Standing pilosity sparse overall, with erect setae absent from antennal scapes and legs. Coloration uniformly castaneous throughout, lacking a contrastingly darker head capsule. Camponotus castaneus is most similar to C. americanus but differs by its uniformly colored head and mesosoma (head darker and clypeus paler in C. americanus), absence of dorsal infuscation on the mesosoma, and generally sparser pilosity.
Identification
Descriptions for each caste are based on examination of MEM specimens.
Minor worker. TL: 6.92-8.50 mm; HL:1.81-2.02 mm; HW: 1.28-1.42 mm; SL: 2.30-2.58 mm; ML: 2.90-3.14 mm; EL: 0.49-0.53 mm.
Head distinctly longer than broad in full-face view; lateral margins subparallel to weakly convex, rounding smoothly into a straight occipital margin. Eyes small, weakly convex, and only slightly protruding from lateral margins. Clypeus ecarinate, its anterior margin straight and non-projecting. Mandibles triangular, coarsely punctate, armed with 4–5 teeth. Frontal carinae short, weakly developed, and not strongly diverging posteriorly. Antennal scapes long and slender, surpassing posterior cephalic margin by nearly one-half of their length; scapes without erect setae.
Mesosoma low and slender in profile, dorsal outline evenly arched; pronotum gently convex; mesonotum weakly domed; propodeum rouded, dorsal face distinctly shorter than declivitous face. Petiole nodiform and robust, lateral margins evenly rounded; node higher than long in profile. Gaster short-ovoid.
Sculpture generally dull. Head and mesosoma finely and superficially shagreened; gaster faintly coriaceous, weakly shining.
Pilosity sparse overall. Anterior clypeal margin fringed with short setae. Erect setae on head and mesosoma few and arranged in discrete pairs: two pairs on pronotum, three on mesonotum, two near propodeal angles, and a transverse row on the vertex. Petiolar dorsum with four erect setae. Antennal scapes and legs lacking erect setae. Pubescence short, dilute, and indistinct throughout.
Coloration dull brown to chestnut; head and mesosoma darker; gaster concolorous to slightly lighter; femora slightly paler, yellowish.
Major worker. TL: 10.88-12.13 mm; HL: 3.12-3.42 mm; HW: 2.93-3.37 mm; SL: 2.96-3.20 mm; ML: 4.14-4.56 mm; EL: 0.64-0.65 mm.
Head slightly broader posteriorly than anteriorly in full-face view; lateral margins evenly rounded, posterior margin shallowly excised. Eyes moderately convex. Mandibles triangular, armed with 6–7 teeth, their surface coarsely and uniformly punctate. Clypeus medially convex, ecarinate to weakly carinate; anterior margin broadly rounded and non-projecting, lateral margins weakly sinuate and faintly crenulate. Frontal carinae lyrate and widely spaced; frontal area extremely reduced; frontal groove distinct. Antennal scapes relatively long, surpassing occipital corners by approximately one-third of their length.
Mesosoma moderately high, slender, and laterally compressed; dorsal outline evenly arched in profile. Propodeal angle indistinct; dorsal face approximately twice the length of the declivitous face. Petiole thick, with strongly convex anterior face, flattened posterior face, and blunt dorsal margin.
Sculpture and integument strongly shining throughout; surface very finely shagreened.
Pilosity sparse. Yellow erect setae present along the anterior clypeal margin and on mandibles; absent from lateral surfaces of head, antennal scapes, and legs except near apices. Mesosoma bearing eight pairs of erect setae on pronotum, 4–5 pairs on mesonotum, and four pairs near propodeal angles. Pubescence extremely short, dilute, and difficult to discern.
Coloration predominantly yellow to yellowish red; head and gaster somewhat darker. Mandibles, antennal scapes, anterior clypeal margin, and genae very dark red to blackish; tibiae and tarsi sometimes infuscate; mandibular teeth black.
Queen. TL: 15.60-17.20 mm; HL: 3.26-3.40 mm; HW: 3.30-3.36 mm; SL: 2.80-2.96 mm; ML: 5.66-6.94 mm; EL: 0.74-0.80 mm.
Similar to major worker but distinctly larger, with fully developed alate mesosoma.
Head slightly broader than mesosoma in dorsal view; lateral margins straight and gently tapering anteriorly; occipital margin shallowly concave to nearly straight. Ocelli well developed and prominent. Mandibles triangular, armed with 6–7 teeth. Antennal scapes long, surpassing posterior cephalic corners.
Mesosoma robust and voluminous. Mesoscutum broad and weakly convex; mesoscutellum evenly rounded. Wings long, whitish to faintly yellow-infuscate, with ferruginous veins and pterostigma. Petiole strongly compressed anteroposteriorly; dorsal margin sharp, distinctly emarginate medially. Gaster elongate-ovoid, darker than mesosoma, tergites with faintly lustrous posterior bands.
Sculpture and integument shining throughout; surface very finely shagreened; mandibles coarsely punctate.
Pilosity sparse. Erect setae short, yellow, and primarily restricted to anterior clypeal margin, dorsal mesosoma, and gaster; absent from antennal scapes and legs except near apices. Propodeal declivity lacking standing setae. Pubescence extremely short and dilute.
Coloration light brown to yellowish brown, generally deeper than in workers; head and gaster darker; femora paler than tibiae and tarsi.
Male. TL: 8.72-9.60 mm; HL: 1.58-1.72 mm; HW: 1.28-1.46 mm; SL: 2.18-2.24 mm; ML: 3.60-4.14 mm; EL: 0.56-0.60 mm.
Head longer than broad in full-face view, slightly broader posteriorly; genae weakly concave and subparallel, approximately equal in length to the large, strongly protruding eyes. Clypeus convex, ecarinate, with broadly rounded anterior margin. Mandibles reduced, spatulate and apically truncate, weakly dentate to nearly edentate. Frontal region faintly elevated medially, bearing a short longitudinal sulcus between antennal insertions. Antennae filiform and slender; scapes surpassing posterior cephalic margin.
Mesosoma robust; mesoscutum evenly convex; mesoscutellum rounded; propodeum smoothly convex, lacking a differentiated dorsal and declivitous face. Wings whitish to faintly infuscate, with ferruginous veins. Petiole short and thick, anterior and posterior faces forming triangular planes converging dorsally; dorsal margin blunt. Gaster ovoid, darker than mesosoma. Legs elongate and slender.
Sculpture and integument shining throughout, surface finely shagreened.
Pilosity extremely sparse; erect setae absent from head and dorsal mesosoma except on metapleural lobe. Pubescence short, dilute, and inconspicuous.
Coloration similar to queen but generally lighter; mesonotum often longitudinally streaked with darker brown; mandibles only slightly darker than head.
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 castaneus is a widespread habitat generalist occurring across a broad range of forested and open environments, including oak–hickory, mixed pine–hardwood, longleaf pine, bottomland hardwood, flatwoods, prairies, glades, and sandy scrub, as well as disturbed habitats such as campgrounds, orchards, yards, and cultivated fields. Colonies nest in rotting logs and stumps, exposed soil, or soil beneath objects, and may also occur at the bases or within the bark of pines and hardwoods. Frequent capture in Lindgren funnel traps baited with α-pinene suggests regular trunk-foraging activity, while repeated attraction to blacklight and mercury vapor lamps indicates conspicuous nocturnal dispersal flights; alates have been collected from early May through mid-June and again in September. This species is not considered a serious pest of wood products and typically enters buildings only while foraging rather than nesting. Overall, C. castaneus is ecologically beneficial, contributing to predation, scavenging, and soil turnover, with economic impact largely neutral and limited to occasional nuisance encounters near human structures.
Pest Status
Camponotus castaneus may occasionally act as a minor structural nuisance, primarily whenworkers enter buildings while foraging, especially at night. However, colonies typically nest in rotting wood, soil, or other natural substrates rather than sound structural timber, and indoor nesting is uncommon. As a result, reports of structural damage are rare and generally limited to preexisting decayed wood. When present near human dwellings, the species is best classified as a low-impact nuisance rather than a true structural pest, with overall economic importance minimal.
Distribution
Eastern United States from New York south to Florida and Puerto Rico, and west to Oklahoma and Texas. Widely distributed throughout the southeastern United States, with records from Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Tennessee, and Virginia. Additional records are known from Delaware, the District of Columbia, Illinois, Indiana, Maryland, New Jersey, New York, Oklahoma, and Puerto Rico.
Literature Cited
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