Cephalotes opacus

Little is known about the biology of .

Identification
A member of the atratus clade appearing as sister species of Cephalotes placidus. Its main apomorphy, in the worker, are the short, cylindrical propodeal spines. (de Andrade and Baroni Urbani 1999)

Distribution based on Regional Taxon Lists
Neotropical Region: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Venezuela.

Nomenclature

 *  opacus. Cephalotes opacus Santschi, 1920f: 147 (w.) GUYANA. De Andrade & Baroni Urbani, 1999: 149 (q.m.). Combination in Eucryptocerus: Kempf, 1951: 131; in Cephalotes: De Andrade & Baroni Urbani, 1999: 147. Junior synonym of placidus: Kempf, 1959a: 92. Revived from synonymy and senior synonym of abdominalis: De Andrade & Baroni Urbani, 1999: 147.
 * abdominalis. Cephalotes abdominalis Santschi, 1929d: 302 (w.) FRENCH GUIANA. Combination in Eucryptocerus: Kempf, 1951: 129. Junior synonym of opacus: De Andrade & Baroni Urbani, 1999: 147.

Worker
de Andrade and Baroni Urbani (1999) - Head subquadrate. Border of the frontal carinae irregularly crenulate, with a small, median denticle. Eyes globose, behind of the scrobes. Vertexal angles with two pairs of teeth with lamellaceous border; the anterior tooth smaller and separate from the posterior one by a deep notch. Vertexal margin prolonged backwards into a visible neck. Vertex with a pair of denticles, more developed in larger specimens. Mandibles, laterally, with a superficially carinate tumulus.

Mesosoma. Anterior pronotal border with a superficial incision in the middle and with a developed scapular angle laterally. Anterior third of the pronotal sides straight, second third with a pair of long spines with bidenticulate tip, posterior third gently converging behind. Pronotal dorsum with a pair of denticles more developed in large specimens. Pronotal suture marked on the sides. Mesonotal sides unarmed, superficially marginate and gently converging posteriorly. Propodeal suture well impressed, less marked in the middle. Basal face of the propodeum with straight, weakly marginate sides and separate from the declivous one by a pair of cylindrical spines. Propodeal spines as long as half or less than half of the maximum length of the basal face of the propodeum. Declivous face of the propodeum straight and laterally separate from the broad metapleura by a carina.

Petiole subcylindrical, with truncate anterior face, dorsally and laterally unarmed and gently converging posteriorly. Postpetiole slightly higher than the petiole; anterior half of the postpetiolar sides convex or truncate, posterior half converging backwards.

Gaster with a pair of anterior lamellae or simply shortly marginate.

Legs. Mid and hind femora without angle or denticle medially but with a pair of faint longitudinal carinae on the two posterior thirds. Hind basitarsi long, laterally compressed and slightly broadening at the base.

Sculpture. Head entirely minutely and superficially reticulate and with foveae diminishing in size anteriorly, denser on the on their posterior third, very superficial on the frons and on the hypostomal area of some specimens. Mesonotum minutely reticulate and with variably distributed and impressed foveae; in some specimens the foveae are smaller, sparser and more superficial on the mesonotum and on the propodeum. Pedicel minutely reticulate and with dense, mall foveae. Gaster and legs reticulate. Femora with thin, short, irregular, superficial rugosities. Centre of the first gastral tergite and sternite superficially reticulate and shining.

Pilosity. Each fovea with a thin, short, appressed, pointed hair; similar hairs but not originating from the foveae on the legs and on the gaster. Anterior border of the frontal carinae, vertexal angles, pronotal spines and legs with rare, short, suberect, clavate hairs; similar hairs but longer and slender on the legs and on the posterior border of the gastral tergites and sternites. Sternites with long, pointed hairs.

Colour. Black and variably opaque. Frontal carinae with two pairs of infuscate dark-reddish, opaque maculae. Border of the vertexal angles, of the gastral lamellae and tarsomeres dark-ferrugineous.

Measurements (in mm) and indices: TL 6.56-8.70; HL 1.54-2.40; HW 1.94-2.40; EL 0.40-0.48; PW 1.68-2.28; PeW 0.50-0.62; PpW 0.52-0.60; HBaL 0.96-1.20; HBaW 0.19-0.25; CI 115.6-125.9; PI 104.0-115.5; PPeI 336.0-392.8; PPpI 297.1-340.3; HBaI 19.8-21.4.

Soldier
de Andrade and Baroni Urbani (1999) - Differing from the worker for the following characters: frontal carinae gently converging in front of the eyes. Vertexal teeth smaller and without lamellaceous border. Vertex with a pair of larger denticles. Eyes less globose.

Mesosoma. Notch on the anterior pronotal border almost absent. Pronotal sides with thicker and shorter spines. Pronotal dorsum with a pair of broad, flat, triangular teeth. Mesonotal sides unarmed or slightly convex, superficially marginate and gently converging posteriorly. Propodeal suture deeply impressed.

Gaster with a pair of lamellae of variable size.

Measurements (in mm) and indices: TL 10.32-10.60; HL 2.40-2.48; HW 3.00; EL 0.56-0.60; PW 2.84-2.96; PeW 0.72-0.76; PpW 0.80-0.84; HBaL 1.24-1.32; HBaW 0.28; CI 121.0-125.0; PI 101.3-105.6; PPeI 373.7-411.1; PPpI 352.4-355.0; HBaI 21.2-22.6.

Queen
de Andrade and Baroni Urbani (1999) - Head subquadrate, slightly broader than long and with subparallcl sides. Frons gently convex. Frontal carinae converging anteriorly and straight up to the vertexal angles. Frontal carinae broadly crenulate and with a small tooth in the middle. Vertexal angles with a pair of small teeth separate by a concavity from a low, anterior angle, the angle round and poorly projecting. Vertex marked by a pair of triangular teeth. Mandibles as in oculatus.

Mesosoma. Humeral angles bearing a thick, pointed tooth. Pronotal crest well marked, high, with crenulations and interrupted in the middle by a superficial impression. Mesonotum, scutellum, lower mesopleurae and sides of the declivous face of the propodeum as in oculatus. Basal face of the propodeum much lower than the scutellum and short; its sides with a pair of subtriangular spines, slightly diverging backwards.

Petiole with differentiate anterior and posterior faces; anterior face truncate, posterior face gently sloping posteriorly. Petiole unarmed and with the sides weakly converging posteriorly. Postpetiole convex dorsally; sides of the postpetiole slightly convex

Gaster with a thin lateral margin not surpassing the first gastral stigma posteriorly.

Legs as in oculatus.

Sculpture as in oculatus differing only in the size of the foveae, generally larger and sparser on the lower mesopleurae.

Pilosity as in oculatus.

Colour. Black. Tarsomeres brown.

Measurements (in mm) and indices: TL 14.52; HL 2.64; HW 3.04; EL 0.64; PW 3.24; PeW 0.96; PpW 1.08; HBaL 1.44; HBaW 0.31; CI 115.1; PI 93.8; PPeI 337.5; PPpI 300.0; HBaI 21.5.

Male
de Andrade and Baroni Urbani (1999) - Head (eyes included) slightly less than 1/3 broader than long. Vertexal angles, medially, with a broad, triangular denticle continuing into a longitudinal, incomplete carina almost reaching the internal border of the eye. Vertexal margin prolonging backwards into a broad neck. Vertex dorsally gently convex and bearing salient ocelli. Compound eyes convex, in the middle of the sides of the head. Frontal carinae high, slightly convex, broad, not reaching the impair ocellus but diverging backwards into a thin, irregular margin. Frons flat posteriorly, slightly declivous anteriorly. Clypeus convex posteriorly and with almost truncate anterior face. Mandibles slim, laterally with a superficial carina. Scapes thick and short, not reaching the posterior border of the eyes. Funiculi thickening from the base to the apex.

Mesosoma. Pronotum in dorsal view with the sides diverging backwards. Mesonotum convex in side view; only pair Mayrian furrows impressed and visible. Scutellum convex and higher than the mesonotum, its sides converging posteriorly. Basal face of the propodeum much lower than the scutellum; dorsum of the basal face sloping backwards, but differentiate from the declivous one; sides of the basal face gently converging backwards, with the posterior half bearing a short, carinate, triangular tooth. Declivous face laterally marked by a pair of longitudinal, convergent carinae.

Petiole and postpetiole cylindrical; anterior petiolar face truncate and dorsally carinate.

Gaster very narrow and elongate; the first segment ca. 1.5 times longer than broad.

Sculpture. Head dorsum minutely reticulate and with sparse, irregular, thin rugosities; vertexal angles with irregular foveae; frons with very superficial foveae, small foveae. Ventral part of the head with the same type of sculpture as on the vertexal angles, the foveae diminishing in size and more superficial on the anterior part. Pronotum, mesonotum and scutellum reticulate and with sparse, irregular foveae; the same sculpture but separated by short, irregular rugosities on the basal face of the propodeum, on the anterior half of the petiole and on the sides of the postpetiole. Pedicel, pleurae, declivous face of the propodeum and first gastral tergite deeply reticulate; the reticulation less impressed and more shining on the remaining tergites, on the sternites and on the legs.

Pilosity. Body with three types of hairs: (1) suberect, long hairs, more dense on the head, on the mesosoma and on the apex of the gaster, sparse on the pedicel and on the legs, shorter on the first sternite; (2) short, sparse, appressed on the legs and on the gaster, rare on the pedicel; (3) similar to type (2) but longer, thicker and dense on the internal, anterior and posterior faces of the tibiae and on the tarsomeres.

Colour. Head, mesosoma and pedicel opaque black. Two anterior thirds of the first gastral tergite dark reddish brown. Remaining tergites, sternites and legs ferrugineous and slightly shining.

Measurements (in mm) and indices: TL 8.80; HL 1.36; HW 1.48; EL 0.51; PW 1.24; PeW 0.65; PpW 0.70; HBaL 1.16; HBaW 0.16; CI 108.8; PI 119.3; PPcI 190.8; PPpI 177.1; HBal 13.8.

Type Material
de Andrade and Baroni Urbani (1999):

Worker. Type locality: St. Jean du Maroni (French Guyana). Type material: holotype worker (unique), without head in (examined).

Cephalotes abdominalis Worker. Type locality: St. Jean du Maroni (French Guyana). Type material: lost; the original pin is still in the but no ant is glued to the label nor can it be found in the drawer.

References based on Global Ant Biodiversity Informatics

 * Bezdeckova K., P. Bedecka, and I. Machar. 2015. A checklist of the ants (Hymenoptera: Formicidae) of Peru. Zootaxa 4020 (1): 101–133.
 * Brandao, C.R.F. 1991. Adendos ao catalogo abreviado das formigas da regiao neotropical (Hymenoptera: Formicidae). Rev. Bras. Entomol. 35: 319-412.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Fichaux M., B. Bechade, J. Donald, A. Weyna, J. H. C. Delabie, J. Murienne, C. Baraloto, and J. Orivel. 2019. Habitats shape taxonomic and functional composition of Neotropical ant assemblages. Oecologia 189(2): 501-513.
 * Franco W., N. Ladino, J. H. C. Delabie, A. Dejean, J. Orivel, M. Fichaux, S. Groc, M. Leponce, and R. M. Feitosa. 2019. First checklist of the ants (Hymenoptera: Formicidae) of French Guiana. Zootaxa 4674(5): 509-543.
 * Kempf W. W. 1951. A taxonomic study on the ant tribe Cephalotini (Hymenoptera: Formicidae). Revista de Entomologia (Rio de Janeiro) 22:1-244
 * Kempf W. W. 1960. Insecta Amapaensia. - Hymenoptera: Formicidae (segunda contribuição). Studia Entomologica (n.s.)3: 385-400.
 * Kempf W. W. 1974. Taxonomic and faunistic notes on some Neotropical Cephalotini ants (Hymenoptera, Formicidae). Revista Brasileira de Entomologia 18: 67-76.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Kusnezov N. 1953. La fauna mirmecológica de Bolivia. Folia Universitaria. Cochabamba 6: 211-229.
 * Santschi F. 1920. Nouvelles fourmis du genre Cephalotes Latr. Bulletin de la Société Entomologique de France. 1920: 147-149.
 * Santschi F. 1929. Nouvelles fourmis de la République Argentine et du Brésil. Anales de la Sociedad Cientifica Argentina. 107: 273-316.
 * de Andrade, M.L. & C. Baroni Urbani. 1999. Diversity and Adaptation in the ant genus Cephalotes, past and present. Stuttgarter Beitrage zur Naturkunde Serie B 271. 893 pages, Stuttgart