| Cephalotes ustus|
Nothing is known about the biology of Cephalotes ustus.
A member of the clypeatus clade characterised in the worker and in the soldier by the dark brown body, by the head, mesosoma, pedicel and gaster surrounded by a yellow-whitish, opaque lamella, and by the strong body sculpture. (de Andrade and Baroni Urbani 1999)
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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 New General Catalogue, a catalogue of the world's ants.
- ustus. Zacryptocerus ustus Kempf, 1973c: 450, figs. 1-4 (w.) BRAZIL. De Andrade & Baroni Urbani, 1999: 284 (s.). Combination in Cephalotes: De Andrade & Baroni Urbani, 1999: 283.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Total length 7.7 (6.9) mm; maximum head length 2.08 (2.79) mm; maximum diameter of eyes 0.38 (0.37) mm; Weber's length of thorax 2.24 (2.00) mm; maximum width of thorax across pronotum 2.87 (2.71) mm. Deeply fuscous brown, almost black; gaster and tarsomeres black; membranaceous laminate borders of head, thorax, gaster and spines of petiole and postpetiole testaceous. Integument opaque, finely, densely punctulate, including the laminate borders which are not glassy nor hyaline. Dorsum of head, cheeks, dorsum of thorax, of petiole, postpetiolc and gaster, apical half of extensor face of femora, tibiae densely and shallowly foveolate, each foveola being oblong and containing an appressed, canaliculate, golden hair. The same hairs are much more widely scattered, either canaliculate or simple, on gular surface of head, sides of thorax, sides of femora and tibiae, ventral surface of gaster, with the foveolae usually indistinct. Gaster, in addition, very finely reticulate-rugulose. Standing hairs absent.
Head distinctly transverse, sides slightly diverging caudad, occipital angle spinous, acute, the spine with a laterally projecting lobe, smaller yet similar to that of membranaceus. Frontal carinae and occipital borders membranaceous and somewhat upturned. Dorsum of head gently convex on disc in both directions, laterally transversely concave. Clypeal sutures vestigial. Frontal area obsolete. Cheeks immarginate below. Eye stalk entirely fused to the frontal carinae above, the apical part bearing the eye not free. Eyes relatively larger, their maximum diameter equal to the distance between their posterior orbit and the tip of the occipital spine. Thorax as in membranaceus except for the different sculpture already mentioned above; lateral expansions of the pronotum scarcely raised apicad, horizontal, those of propodeum obliquely upturned. Hind femora marginate above on apical half yet not sharply carinate, angulate above in side-view, the angle situated beyond the first third of the femur length. First tarsomere distinctly yet not strikingly longer than tarsomeres 2-5 combined. Petiole, postpetiole and gaster as in membranaceus except for the differences in sculpture, color and pilosity already mentioned above.
de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 6.44-7.28; HL 1.52-1.68; HW 2.40-2.68; EL 0.37; PW 2.56-2.80; PeW 0.92-1.02; PpW 0.88-1.00; HBaL 0.72-0.76; HBaW 0.25-0.27; CI 157.9-163.4; PI 93.7-97.7; PPeI 270.6-283.3; PPpI 276.0-309.1; HBaI 34.7-37.5.
de Andrade and Baroni Urbani (1999) - Head feebly convex. Frontal carinae convex anteriorly; their sides slightly converging over the eyes and continuing to the vertexal angles; the latter in form of broad, pointed teeth interconnected by a broad lamella interrupted in the middle. Vertex with a pair of median teeth equally connected by a carina. Mandibles broad, with a strong lateral carina.
Mesosoma. Pronotal sides with a broad lamella, with convex anterior border and posteriorly converging sides. Pronotal carina wide, superficially interrupted in the middle; its sides forming an obtuse tooth in the middle of the notopleural angle. Promesonotal suture impressed on the sides. Mesonotum with a broad, obtuse tooth. Propodeal suture deeply impressed. Propodeum bearing a pair of long spines round at the apex, its basal and declivous face clearly differentiated. Basal face of propodeum with a broad lamellaceous border with 1-2 denticles anteriorly followed by a round tooth and embedding laterally the propodeal spines. Dorsum of propodeal spines markedly carinated.
Petiole with the anterior border truncate and slightly concave medially; posterior face of the petiole flat. Petiolar spines with lamellaceous round tips directed backwards. Postpetiolar spines as in the petiole, originating from the anterior face of the postpetiolc and curved laterally.
Legs. Fore coxae with a pointed anterior spine. Mid and hind femora forming an angle without denticles. Hind basitarsi flat and broad at the base.
Gaster oval and surrounded by a broad lamellae with a notch on its posterior middle.
Sculpture. Head, mesosoma and pedicel punctate and covered by foveae sparser and shallower on the middle of the frontal carinae and on the meso- and metapleurae. Ventral face of the head with broader foveae than those on the head dorsum; similar foveae but sparser on the propleurae. Posterior half of the declivous face of the propodeum, dorsal half of the metapleura, legs and gaster reticulate-punctate, with faint foveae and anastomosing rugosities on first gastral tergite. Middle of the first gastral sternite shining, with sparse piligerous punctures. Membranaceous border surrounding the body reticulate-punctate.
Pilosity. Each fovea bearing an appressed, canaliculate hair of size proportional to the one of the fovea; gaster covered by dense hairs as on the head. Legs with the same type of hairs as the gaster, but sparser. Thin, sparse, appressed hairs on the legs and on the middle of the first gastral sternite. Apex of the gaster with sparse, long, thick, erect hairs truncate or pointed.
Colour. Dark brown to black. Frontal carinae and vertexal angles yellowish-brown, lamellae of the mesosoma, of the pedicel and of the gaster lighter.
Measurements (in mm) and indices: TL 8.84-8.88; HL 2.12-2.16; HW 2.92-3.00; EL 0.44; PW 3.16; PeW 1.16; PpW 1.08-1.12; HBaL 0.88-0.92; HBaW 0.30; CI 137.7-138.9; PI 92.4-94.9; PPeI 272.4; PPpI 282.1-292.6; HBaI 32.6-34.1.
de Andrade and Baroni Urbani (1999) - Worker. Type locality: Pedra Azul, 800 m (Minas Gerais, Brazil). Type material: Holotype and paratype workers labelled: "Pedra Azul - MG, 800 m, XI-1972, Seabra & Alvarenga, no. 8816, Holotypus and Paratypus", in Museu de Zoologia da Universidade de Sao Paulo, examined.
- 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 284, soldier described, page 283, Combination in Cephalotes)
- Kempf, W. W. 1973c. A new Zacryptocerus from Brazil, with remarks on the generic classification of the tribe Cephalotini (Hymenoptera: Formicidae). Stud. Entomol. 16: 449-462 (page 450, figs. 1-4 worker described)