Cephalotes placidus

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Cephalotes placidus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Cephalotes
Species group: atratus
Species: C. placidus
Binomial name
Cephalotes placidus
(Smith, F., 1860)

Cephalotes placidus P casent0217842.jpg

Cephalotes placidus D casent0217842.jpg

Specimen Label


This species has been collected from a recent treefall, in scrub forest and in a rainforest clearing. Besides these nesting and habitat notes, nothing is known about the biology of Cephalotes placidus.


A member of the atratus clade distinguishable from the other species, in the worker, for the following combination of characters: long, thick propodeal spines, deep foveolate sculpture and broad gastral lamella. The gyne and the male of placidus are similar to Cephalotes opacus but have much stronger body sculpture and longer propodeal spines. (de Andrade and Baroni Urbani 1999)

Keys including this Species


Latitudinal Distribution Pattern

Latitudinal Range: 5.17356° to -14.5°.

Tropical South

Distribution based on Regional Taxon Lists

Neotropical Region: Brazil (type locality), Colombia, Guyana, Peru.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


The biology of many Cephalotes species is not known. Ants in this genus are common in the New World tropics and subtropics and are especially abundant and diverse in the canopies of Neotropical forests. The majority of species are arboreal. Species that live in other strata inhabit smaller trees, bushes or grass stems. These noon-arboreal species, due to their accessibility, are among the better studied members of the genus. There are also species that can be found in downed wood but it is likely the wood housed the colony before it fell to the ground. Soil nests are not known for any species nor do most species appear to extensively excavate plant tissue. They nest instead in preformed cavities. Overall, ants in the genus utilize a wide range of plants. Some species are predictable in their plant use but none appear to have evolved specialized mutualisms with particular plant species.

Worker castes typically include two forms, a worker and soldier, but there are a few species that are monomorphic. The larger soldier caste typically has an enlarged head disk. In some species the head of the soldier is very different from the worker while in others these differences are less pronounced. Queens and soldiers tend to share similar head morphology. Soldiers use their heads to plug the nest entrance. This can be very effective in excluding potential intruders. Other morphological differences between the worker castes are present but these differences have not been studied as well as head moprhology.

The behavioral repertoire of Cephalotes varians has been examined in great detail (ethograms from Wilson 1976, Cole 1980 and Cole 1983). Soldiers do little else besides defend the nest. This specialized soldier behavior is presumed to be the norm for most species. An especially interesting behavior occurs when workers are dislodged from trees: they "fly" towards the tree, often grabbing the trunk well above the ground (video).

Mature nest size varies, by species, from less than a hundred to many thousands of workers. Available evidence suggests most species are monogynous. Queens may mate with multiple males.

The proventriculus of the Cephalotes is peculiar relative to other ants. The morphology of the structure suggests it serves as a powerful pump and filter. This does not appear to lead these ants to have a highly specialized diet as most species appear to be general scavengers. Foragers have been observed feeding on carrion, bird feces, extrafloral nectaries and even tending membracids. Pollen feeding has been observed in some species, and this is somewhat specialized for ants, but it is not evident that any species restricts its diet to this resource in any significant way. Evidence for pollen feeding in Cephalotes has accumulated, in part, via finding digested pollen grains seen in infrabucal pellets. It has been suggested that the morphology of the proventriculus is a specialization for processing pollen.

More research examining all aspects of the biology of Cephalotes is needed. Our present understanding of these ants is largely based on species that live in locations other than the forest canopy, which is where Cephalotes are most common and diverse.



The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • placidus. Cryptocerus placidus Smith, F. 1860c: 76 (m.) BRAZIL. Snelling, R.R. 1966: 38 (w.q.). Combination in Cephalotes: Emery, 1924d: 304; in Eucryptocerus: Kempf, 1959a: 92; in Cephalotes: De Andrade & Baroni Urbani, 1999: 156. Senior synonym of fenestralis: Kempf, 1963c: 437.
  • fenestralis. Cryptocerus fenestralis Smith, F. 1876d: 607 (q.) BRAZIL. Combination in Paracryptocerus: Kempf, 1951: 232. Junior synonym of placidus: Kempf, 1963c: 437.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.



de Andrade and Baroni Urbani (1999) - Head subquadrate, less than one fourth broader than long. Border of the frontal carinae with a small denticle in the middle. Vertexal angles with two pairs of teeth; only the internal tooth with lamellaceous border and ca. twice larger than the external one.

Mesosoma. Anterior pronotal border with a superficial or without a notch in the middle. Pronotal dorsum with a pair of developed denticles. Propodeum with a pair of spines ca. 1.5 longer than the basal face.

Petiole subcylindrical, with truncate anterior face, unarmed and gently converging posteriorly. Postpetiole slightly higher than the petiole; anterior half of the postpetiolar sides broadly convex, in some specimens with truncate apex; posterior half converging posteriorly.

Gaster with a pair of broad lamellae narrowing at the apex.

Legs. Mid and hind femora without angle or denticle medially but with a pair of faint longitudinal carinae on the two posterior thirds. Mid and hind basitarsi long, slightly compressed laterally at the base; their diameter constant through the whole length.

Sculpture. Foveae on the mesosoma and pedicel much deeper than in opacus and oculatus.

Pilosity and colour. As in the other species of the clade.

Measurements (in mm) and indices: TL 8.04-8.80; HL 1.84-2.04; HW 2.24-2.48; EL 0.47-0.49; PW 2.44-2.56; PeW 0.60-0.70; PpW 0.70-0.83; HBaL 1.00-1.16; HBaW 0.23-0.27; CI 119.1-1224 .0; PI 96.9-100.0; PPeI 365.7-380.0; PPpI 308.4-325.7; HBaI 23.0-23.3.


Snelling (1966) - Total length, 11.4 mm.; forewing, 10.9 mm; maximum head width, 3.0 mm; maximum head length (from anterior margin of lateral lobes), 2.9 mm; maximum thoracic width, 3.0 mm. Integument dull black, except the dark reddish-brown apical tarsal segments.

Head, excluding mandibles, very slightly longer than wide; mandibles strongly rugose; clypeus about as broad as long, triangular; frontal carinae slightly convergent anteriorly, margin of lower one-third slightly crenulate, with a few clavate setae occiput with a pair of low, pointed tubercles immediately above posterior ocelli; a low pointed tubercle on each side above eyes, with a similar tubercle immediately behind; front distinctly convex when viewed from above; occipital emargination rather deep; cheeks very broad, almost one-third as broad as head is long.

Pronotum nearly vertical anteriorly; humeral angles projecting forward as a narrow spine when viewed from above, pronotal crest strong laterally, absent medially, carinate, the carina raised on each side of median line as a pair of low humps, entire carina slightly crenulate; mesopleura with small spine above mid coxae; epinotum narrow, with a pair of spines directed caudad, the spines about as long as distance between their bases.

Petiole short, about twice as broad as long, anterior face vertical; postpetiole not swollen dorsally, only slightly swollen laterally; petiole and postpetiole without ventral projections; gaster more elongate than in worker, about one-third longer than broad, first tergite emarginated basally, disc with very fine striae which converge medially, anterior carina of first tergite distinct as far back as spiracle; remaining tergites discally roughened, all tergites with a narrow, dull, impunctate m arginal band; first ventrite dull, sparsely punctate with a few irregular striae laterally; remaining ventrites roughened disc ally; all ventrites with narrow, impunctate apical margins which are slightly more shiny than those of tergites.

Integument generally dull, subopaque, mesoscutum, scutellum and abdomen somewhat shinier. Punctures of front moderate in size, separated by about a puncture diameter, becoming a little finer and sparser below, somewhat less distinct on pronotal lobes j punctures of occiput coarser than those of front, separated by a puncture diameter or less; cheeks rugoso-punctate; punctures of anterior and upper faces of pronotum equal to those of occiput, sparser medially, of lateral face coarse, rather close; punctures of mesoscutum slightly elongated, separated by a puncture diameter or less, becoming sparser and fainter laterad; those of disc about equal to those of occiput; punctures of upper mesopleural plate slightly finer than those of adjacent portion of pronotum, separated by slightly less than a puncture diameter; punctures of lower half of mesopleura, entire metapleura, lateral and posterior faces of epinotum obscure, scattered, the integument opaque, minutely granulose; punctures of scutellum slightly elongate, equal to those of mesoscutum, separated by a puncture diameter or less the integument slightly more shiny than elsewhere; punctures of basal face of epinotum coarse, deep, subcontiguous. Wings fuscous infuscate, except for clear submarginal cell; marginal cell closed and appendiculate apically, about 3.5 times as long as wide; submarginal cell about three-fourths as long as marginal; otherwise as figured by Kempf (1959:93) for the male.

de Andrade and Baroni Urbani (1999) - de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 12.86-13.70; HL 2.48-2.56; HW 3.00-3.12; EL0.64; PW 3.04-3.20; PeW 0.92-1.00; PpW 1.08-1.10; HBaL 1.32; HBaW 0.32-0.34; CI120.0-121.9; PI 97.5-98.7; PPeI 320.0-330.4; PPpI 281.5-291.0; HBaI 25.7.


Kempf (1959), translated in de Andrade and Baroni Urbani (1999) - Total length 9.7 mm; length of the cephalic capsule 1 .45 mm; head width, including the eyes, 2.21 mm; length of the thorax 3.12 mm; length of the fore wing 7.6 mm. Black; funicular segments II - XII, legs, except the coxae, and gaster ferruginous. integument opaque, finely and densely punctuate; first gastral tergite, particularly in the center, and legs, particularly on the extensor face of the femora, with sculpture more superficial and slightly shining. Head with larger foveolae, superficial and sparse; with very short rugae disposed radially around the eyes; occiput rugose-reticulate. Pronotum, shield and scutellum with foveolae slightly larger but equally superficial and sparse. Basal face of the epinotum irregularly reticulate-rugose; declivous face with regular rugae, vertical and thinner. Dorsum and sides of the peduncular segments with fine, spaced, longitudinal rugae. Erect pilosity thick, yellowish, abundant on the body, nearly entirely lacking on the first gastral tergite and on the legs, excepted the flexor face of the femora and of the tibiae. Gaster with thin and short , sparse hairs, adherent to the integument. Pubescence more dense on the legs, very dense and very short on the funiculi.

Head transverse; interocular distance slightly larger than the length of the cephalic capsule. Clypeus considerably convex, with anterior face sloping and truncated in the middle, clearly separate from the superior face, the two forming a right angle, when seen in profile. Occipital angles with a triangular tooth large and projecting. Thoracic shoulders obtuse, not marked. Basal face of the epinotum with lateral borders converging behind, the triangular lobes of the posterior angle with pointed and sharp borders; postero-median impression without distinct margination in the middle. First tarsomere of the middle and hind legs slightly compressed, not remarkably enlarged. The two peduncular segments bear on each side a projecting tubercle, those of the petiole more ventral, not visible when seen from top. First gastral tergite 1 1/3 times longer than wide, the base superficially impressed in the middle of the articulation of the postpetiole.

Wings slightly darkened, with the venation dark-brown. Fore wing with black pterostigma, cubital cell nearly light and hyaline. Hind wing with venation originating from the anterior side of the radius, in the middle of the first abscissa, and with 9-10 hamuli.

de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 7.72-9.40; HL 1.12-1.36; HW 1.48-1.76; EL 0.52-0.65; PW 1.28-1.60; PeW 0.56-0.72; PpW 0.64-0.80; HBaL 1.16-1.28; HBaW 0.16- -0.20; CI 120.6-132.1; PI 102.8-119.3; PPeI 220.0-235.3; PPpI 193.7-222.2; HBaI 13.8-15.6.

Type Material

de Andrade and Baroni Urbani (1999):

Male. Type locality: Sao Paulo de Olivenca (Amazonas, Brazil). Type material: holotype male labelled: 1 st label "St. Paulo Braz.", 2nd label "Cryptocerus placidus Smith", 3rd label "Coll. Smith 1829", 4th label (pink) "Eucryptocerus placidus (Sm.) Holotypus [added by Kempf]”, 5th label "Eucryptocerus placidus (Fr. Smith, 1 860) det. W. W. Kempf", 6th label "Type Hym.: 1041 Cryptocerus placidus Smith Hope Dept. Oxford", in Oxford University Museum of Natural History, examined. A second specimen in The Natural History Museum, labeled "C. placidus, type. Sm., Journ. Ent. I.76, 59 2", examined, is likely to belong to another species which we are unable to identify. We consider Kempf’s (1959) re-description of the Oxford specimen as a lectotype designation.

Cryptocerus fenestralis Gyne. Type locality: Sao Paulo de Olivenca (Amazonas, Brazil). Type material: holotype gyne labelled "Cryptocerus fenestralis., (type) Smith, St. Paul, 70 16" in The Natural History Museum (Kempf, 1963: 437), examined.

The following notes on F. Smith type specimens have been provided by Barry Bolton (details):

Cryptocerus placidus

Holotype male in Oxford University Museum of Natural History. Labelled “S. Paulo Brazil.”


  • de Andrade, M. L.; Baroni Urbani, C. 1999. Diversity and adaptation in the ant genus Cephalotes, past and present. Stuttgarter Beitrage zur Naturkunde Series B (Geolgie and Palaontologie). 271:1-889. (page 156, Combination in Cephalotes)
  • Emery, C. 1924f [1922]. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [concl.]. Genera Insectorum 174C: 207-397 (page 304, Combination in Cephalotes)
  • Kempf, W. W. 1959a. Sôbre algumas formigas Cephalotini do Museu de Oxford (Hymenoptera, Formicidae). Rev. Bras. Biol. 19: 91-98 (page 92, Combination in Eucryptocerus)
  • Kempf, W. W. 1963c. Nota sinonímica acêrca de formigas da tribo Cephalotini (Hymenoptera, Formicidae). Rev. Bras. Biol. 23: 435-438 (page 437, Senior synonym of fenestralis)
  • Oliveira, A.M., Powell, S., Feitosa, R.M. 2021. A taxonomic study of the Brazilian turtle ants (Formicidae: Myrmicinae: Cephalotes). Revista Brasileira de Entomologia 65, e20210028 (doi:10.1590/1806-9665-rbent-2021-0028).
  • Smith, F. 1860c. Descriptions of new genera and species of exotic Hymenoptera. J. Entomol. 1: 65-84 (page 76, male described)
  • Snelling, R. R. 1966. The female of Eucryptocerus placidus (F. Smith) (Hymenoptera: Formicidae). Bull. South. Calif. Acad. Sci. 65: 37-40 (page 38, worker, queen described)

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.
  • Escalante Gutiérrez J. A. 1993. Especies de hormigas conocidas del Perú (Hymenoptera: Formicidae). Revista Peruana de Entomología 34:1-13.
  • Fernández F., E. E. Palacio, W. P. Mackay, and E. S. MacKay. 1996. Introducción al estudio de las hormigas (Hymenoptera: Formicidae) de Colombia. Pp. 349-412 in: Andrade M. G., G. Amat García, and F. Fernández. (eds.) 1996. Insectos de Colombia. Estudios escogidos. Bogotá: Academia Colombiana de Ciencias Exactas, Físicas y Naturales, 541 pp
  • Fernández F., and E. E. Palacio. 1995. Hormigas de Colombia IV: nuevos registros de géneros y especies. Caldasia 17: 587-596.
  • Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
  • 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. 1959. Sôbre algumas formigas Cephalotini do Museu de Oxford (Hymenoptera, Formicidae). Revista Brasileira de Biologia 19: 91-98.
  • Kempf W. W. 1960. Insecta Amapaensia. - Hymenoptera: Formicidae (segunda contribuição). Studia Entomologica (n.s.)3: 385-400.
  • Kempf W. W. 1963. Nota sinonímica acêrca de formigas da tribo Cephalotini (Hymenoptera, Formicidae). Revista Brasileira de Biologia 23: 435-438.
  • Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
  • Wilson, E.O. 1987. The Arboreal Ant Fauna of Peruvian Amazon Forests: A First Assessment. Biotropica 19(3):245-251.
  • 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