Cephalotes fossithorax

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Cephalotes fossithorax
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Cephalotes
Species: C. fossithorax
Binomial name
Cephalotes fossithorax
(Santschi, 1921)

Cephalotes fossithorax casent0912598 p 1 high.jpg

Cephalotes fossithorax casent0912598 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Cephalotes fossithorax.


A member of the fiebrigi clade differing from its next outgroup species, Cephalotes jheringi, and from its next ingroup species, Cephalotes supercilii, in the worker, soldier and gyne by the erect, very short, truncate body hairs.

Keys including this Species


Latitudinal Distribution Pattern

Latitudinal Range: -40.421° to -40.421°.

Tropical South

Distribution based on Regional Taxon Lists

Neotropical Region: Argentina (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.


Explore-icon.png Explore Overview of Cephalotes biology 
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. ‎


Images from AntWeb

Cephalotes fossithorax casent0912599 d 1 high.jpgCephalotes fossithorax casent0912599 p 1 high.jpgCephalotes fossithorax casent0912599 h 1 high.jpgCephalotes fossithorax casent0912599 l 1 high.jpg
Syntype of Cephalotes fossithoraxWorker. Specimen code casent0912599. Photographer Will Ericson, uploaded by California Academy of Sciences. Owned by NHMB, Basel, Switzerland.


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

  • fossithorax. Cryptocerus fossithorax Santschi, 1921h: 125, fig. 1 (s.w.) ARGENTINA (Rio Negro).
    • Type-material: 1 syntype soldier, syntype workers (number not stated).
    • Type-locality: Argentina: Río Negro (Hildemann).
    • Type-depositories: MZSP, NHMB (other possible syntypes in MACN).
    • De Andrade & Baroni Urbani, 1999: 638 (m.).
    • Combination in Paracryptocerus (Harnedia): Kempf, 1958a: 58;
    • combination in Zacryptocerus: Brandão, 1991: 386;
    • combination in Cephalotes: De Andrade & Baroni Urbani, 1999: 635.
    • Status as species: Kempf, 1958a: 58 (redescription); Kempf, 1972a: 177; Brandão, 1991: 386; Bolton, 1995b: 425; De Andrade & Baroni Urbani, 1999: 635 (redescription).
    • Distribution: Argentina.

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



Kempf (1958) - Total length 3.8-4.7 mm; maximum length of head 1.09-1.37 mm; of thorax 1.07-1.28 mm. Very close to Cephalotes jheringi, from which it differs by the ensemble of the following features:

Color reddish-brown; dorsum of body, especially of head, more or less infuscated; legs usually lighter, yellowish-brown. One specimen is nearly black, with fuscous-ferruginous legs. Shape of head variable, subquadrate to subrectangular (but cephalic index: 0.88-0.90, definitely above bivestitus, with which it agrees to some extent in the shape of the lateral thoracic crest). Sides of head slightly emarginate above eyes, especially in larger specimens, which also show an apparently more elongate head. Sides of pronotum usually, not always, little converging caudad, its border with a denticulate crest. This crest contains at least two of four distinct, acute, strong teeth, and inbetween theses teeth smaller denticles. All teeth are foliaceous. Sides of mesonotum either straight or weakly dentate. Mesoepinotal suture distinct only laterally, absent in the middle. Anterior corner of basal face of epinotum with an obtuse, smaller tooth, followed posteriorly by a larger triangular tooth. Inferior corner of declivous face angulate, or even dentate. Peduncular segments of equal width. Petiole with strong lateral tooth, pointing obliquely backwards. Postpetiole with the customary lateral spines, the tips of which are rounded in front, and pointed behind. Postpetiole strongly convex dorsally. Anterolateral lobes of the usually rather short gaster thick, prominent, rounded, their borders at most very bluntly marginate, not depressed, nor forming a thin edge. Sculpture and pilosity not visibly different from peltatus.

de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 3.77-4.36; HL 0.88-1.04; HW 0.98-1.14; EL 0.24-0.27; PW 0.83-0.97; PeW 0.47-0.51; PpW 0.40-0.51; HBaL; HBaW 0.09-0.11; CI 109.6-111.4; PI 117.5-118.1; PPeI 176.6-190.2; PPpI 169.4-190.2; HBaI 29.7-33.3.


Kempf (1958) - Total length 6.5-7.3 mm; maximum length of head disc 1.75-2.10 mm; of thorax 1.71-1.86 mm. Likewise very similar to jheringi, except for the combination of the following features:

Black; anterolateral portion and lateral border of cephalic disc yellow to reddish-brown; a yellowish spot on each shoulder of the larger specimen. Gaster and legs fuscous-ferruginous. Head disc completely marginate, more or less rounded postero-laterally; lateral borders not raised, especially in larger specimen, which has the anterolateral portion of disc completely flat, not excavated. Clypeus with less pronounced teeth on the anterior border, its lateral sutures less distinct than in jheringi, not forming a prominent ridge. Foveolae of floor of head disc slightly more crowded than in jheringi, about 18 pits in a transverse row at the level of the eyes. Occipital lobes with a blunt tooth. Thorax with a transverse pronotal carina, which is not interrupted mesally in the larger worker. Apex of lateral mesonotal lobe not truncate, but subtriangular. Sides of basal face of epinotum without a prominent lateral lobe in larger specimen, with a triangular lobe in smaller specimen. Sculpture and pilosity much the same as in jheringi, with the exception of the projecting setulae on the rim of the head disc, which are fine and pointed at tip.

de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 5.94-7.06; HL 1.44-1.72; HW 1.54-1.80; EL 0.32-0.36; PW 1.48-1.72; PeW 0.65-0.80; PpW 0.66-0.84; HBaL 0.37-0.43; HBaW 0.11-0.14; CI 104 .6-106.9; PI 104.0-104.6; PPeI 215.0-227.7; PPpI 204.8-224.2; HBaI 29.7-32.5.


de Andrade and Baroni Urbani (1999) - Head almost flat to slightly concave anteriorly and gently convex posteriorly, with disc. Sides of the disc strongly crenulate; posterior part of the sides of the disc converging before the eyes and connected with a faint, convex carina. Vertexal angles lower than the disc, convex and with crenulate border. Clypeal border concave. Mandibles carinate, the carina impressed. Dorsal border of the antennal scrobes with a crenulate carina ending in a small denticle before the eyes. Eyes convex and not hidden by the disc. Ocelli distant from the vertexal margin.

Mesosoma flat in side view. Pronotum anteriorly sloping. Humeral angles obtuse, their sides parallel. Pronotal carina superficially marked from the sides to the center where, in some specimens, it is interrupted by a superficial furrow. Promesonotal suture impressed. Mesonotum and scutellum on the same plane and flat. Propodeum with well differentiated basal and declivous faces. Basal face converging posteriorly and bearing a pair of small, round denticles or lobes and a pair of broad, round teeth slightly directed laterally. Declivous face gently concave on the sides and converging posteriorly.

Petiole with differentiated anterior and posterior faces; anterior face sloping; posterior face short. Sides of the petiole with a pair of short, round or obtuse denticles. Postpetiole broadly convex, in some specimens with a gentle concavity in the middle. Postpetiolar sides with a pair of thick, broad, anterior lobes bearing an obtuse denticle posteriorly.

Gaster oval, with a broad, protruding anterolateral lobe.

Hind femora neither angulate nor denticulate. Hind basitarsi more compressed apically than distally and without a broad base.

Sculpture. Head dorsum reticulate and covered by large foveae broader than their interspaces, or, in some specimens, contiguous each other. Frontal carinae with foveae shallower than those on the head dorsum. Sides of the head densely foveolate. Ventral part of the head with irregular foveae variably clumped and shaped as broad reticulation. Pronotum, scutellum and upper mesopleurae reticulate with superimposed dense foveae, less dense on the anterior part of the pronotum. Mesonotum, propleurae and lower mesopleurae reticulate, with superimposed sparse and shallow foveae. Basal face of the propodeum, posterior face of the petiole, postpetiole reticulate-foveolate, the foveae agglomerate and irregular in shape. Declivous face of the propodeum and metapleurae reticulate and with faint, irregular, longitudinal rugosities, the same rugosities but rarer on the pro- and mesopleurae. Gaster, anterior face of the petiole and legs reticulate. Anterior half of the first gastral tergite and sternite and extensor face of the legs with irregular, longitudinal, anastomosing rugulosities which may or may not cover most of the first tergite. Gaster with sparse, small, piligerous foveae. Posterior half of the first gastral sternite and remaining sternites faintly reticulate and shining.

Pilosity. Each fovea with an appressed, short sensillum auricillicum. Legs and gaster apparently with the same appressed hairs as those in the foveae but thinner. Body with sparse, short, thin, suberect, truncate hairs, these hairs are very evident on each crenulation of the frontal carinae and on the sides of the body. Posterior borders of the gastral tergites and whole sternites with the same type of hairs as those on the crenulation of the frontal carinae but longer; rare, long and pointed hairs on the posterior border of the sternites.

Colour. Dark ferrugineous to light brown. Frontal carinae, sides of the head over the eyes, pronotal sides and extensor face of the tibiae yellowish-orange to light ferrugineous; remaining parts of the legs ferrugineous with darker tarsi. Gaster with two pairs of oval yellow spots, the first pair anterolateral, reaching the stigma, the second one on the posterolateral third of the gaster but not reaching the border of the tergite. Body opaque with superficially shining head.

Measurements (in mm) and indices: TL 8.08-8.22; HL 1.48-1.52; HW 1.50-1.56; EL 0.34-0.36; PW 1.48-1.52; PeW 0.64-0.67; PpW 0.77; HBaL 0.43-0.45; HBaW 0.14-0.15; CI 101.3-102.6; PI 101.3-102.6; PPeI 220.9-237.5; PPpI 192.2-197.4; HBaI 32.5-33.3.

Type Material

de Andrade and Baroni Urbani (1999) - Worker and soldier. Type locality: Viedna (Rio Negro, Argentina). Type material: 4 syntypes (one soldier and three workers) in Naturhistorisches Museum, Basel (examined); one syntype worker in Museu de Zoologia da Universidade de Sao Paulo (examined); several workers and soldiers from the same nest as the type in the collection of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (Kempf, 1958 a), not available for the present study.


References based on Global Ant Biodiversity Informatics

  • 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