Cephalotes olmecus

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Cephalotes olmecus
Temporal range: middle Miocene
Mexican amber, Chiapas, Mexico
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Cephalotes
Species: C. olmecus
Binomial name
Cephalotes olmecus
De Andrade, 1999

A fossil species known from Mexican amber.

Identification

A member of the grandinosus clade differing from all the other species of the clade in the worker by the presence of a narrow, crenulate crest on the dorsum of the fore femora, and in the soldier by the strongly crenulate carinae on the dorsum of the fore femora. (de Andrade and Baroni Urbani 1999)

Key to Cephalotes Workers

Distribution

This taxon was described from Mexican amber.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

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.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • olmecus. †Cephalotes olmecus De Andrade, in De Andrade & Baroni Urbani, 1999: 425, figs. 15A-B, 194, 195 (s.w.) MEXICAN AMBER.

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

Description

Worker

Head broader than long. Frontal carinae weakly and minutely erenulate. Vertexal angles broad, round and membranaceous. Vertcxal margin concave. Mandibles with lateral carina. Antennal club two jointed.

Mesosoma. Scapular angles absent or not visible in dorsal view. Anterior pronotal border straight; pronotal sides with a broad, membranaceous expansion, anteriorly subround and narrowing posteriorly. Promesonotal suture absent. Mesonotal sides with a pair of triangular, membranaceous teeth. Propodeal suture deeply impressed. Deelivous face of the propodeum gently sloping backwards. Basal and deelivous faces of the propodeum with a broad membranaceous expansion originating cranially on the basal face and broadening backwards; margin of the membranaceous expansion of the propodeum minutely and superficially crenulate.

Petiole with the anterior face truncate; sides of the petiole with a broad, round, wing-shaped, membranaceous expansion directed laterally. Postpetiole with a comparably broad, wing-shaped, membranaceous expansion with round apex and directed forwards.

Gaster suboval and with broad, anterolateral, membranaceous expansions not surpassing the stigma backwards.

Mid and hind femora angulate and with two membranaceous crests on the two distal thirds, one on the dorsal face and another on the ventral face; fore femora with a short dorsal crest. Mid and hind basitarsi with flat and broad base.

Sculpture. Head dorsum, mesosoma and pedicel minutely reticulate and foveolate, the foveae larger and more regular on the frons, very irregular on the mesosoma, small on the propodeum and on the pedicel. Pronotum and mesonotum with short rugosities between the foveae. First gastral tergite and legs strongly reticulate, the same type of sculpture but more superficial on the first gastral sternite. Anterior half of the first gastral tergite with thin, longitudinal rugosities

Pilosity. Some fovea with a recurved hair. Sides of the frontal carinae, border of the mesosomal and of the peduncular expansions, and legs with short hairs.

Colour. Light brown. Frontal carinae, vertexal angles and membranaceous expansions light ferruginous and semitransparent.

Measurements (in mm) and indices: TL 3.60; HL 0.83; HW 1.07; EL 0.22; PW 0.82; PeW 0.47; PpW 0.53; HBaL 0.20; HBaW 0.12; CI 128.9; PI 130.5; PPeI 174.5; PPpI 154.7; HBaI 60.0.

Type Material

Holotype worker from the Mexican amber sample Mex. 1 and paratype small soldier from the Mexican amber sample H 10-201, both in the GOPC.

Etymology

This species is named after the Olmecs, one of the ancient peoples of Mexico.

References

  • 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 425, figs. 15A-B, 194, 195 soldier, worker described)