Cephalotes sobrius

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Cephalotes sobrius
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Cephalotes
Species: C. sobrius
Binomial name
Cephalotes sobrius
(Kempf, 1958)

De Andrade 1999 Cephalotes OCR - Copy-606 Cephalotes-sobrius.jpg

Only known from the type collection. These were found in plant material being imported into New Jersey (United States) from Guatemala.

Identification

A member of the texanus clade differing from its sister species, Cephalotes lenca, by the absence of thick longitudinal rugosities on the posterior face of the femora of the worker. The workers of sobrius, lenca and Cephalotes curvistriatus are characterised by the thick striae on the mesosoma and on the ventral part of the head. The worker of C. sobrius shares with lenca the angulate hind and mid femora. The soldiers of sobrius and curvistriatus share the floor of the disc not deeply concave, the basal face of the propodeum with irregular denticles, the yellow spot on first gastral tergite, and the anterior fourth of the tergite with longitudinal, irregular rugosities. (de Andrade and Baroni Urbani 1999)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Guatemala (type locality).

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.

  • sobrius. Paracryptocerus (Harnedia) sobrius Kempf, 1958a: 119, pl. 4, fig. 6; pl. 5, fig. 6; pl. 6, fig. 1 (s.w.q.) GUATEMALA. Combination in Zacryptocerus: Hespenheide, 1986: 395; in Cephalotes: De Andrade & Baroni Urbani, 1999: 602.

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

Description

Worker

de Andrade and Baroni Urbani (1999) - Head subquadrate. Vertexal angles round, with weakly crenulate borders. Vertexal margin gently concave. Cheeks marginate above and below Frontal carinae upturned over the eyes. Mandibles laterally carinate.

Mesosoma almost flat in side view. Pronotum in dorsal view with the anterior border convex. Scapular angles absent or not visible in dorsal view. Pronotal sides with a narrow lamella with three pairs of teeth, the anterior pair short, pointed, and slightly direct anteriorly, the second pair similar in size to the first, and the third almost round. Sides of mesonotum with a pair of minute denticles. Promesonotal suture superficially impressed. Propodeal suture marked. Propodeum with differentiate basal and declivous faces; basal face narrowing backwards, with three or four pairs of teeth, the second pair larger than the others, the third and fourth pairs minute, rarely absent in some specimens; declivous face converging posteriorly.

Petiole anteriorly truncate; its anterior border marked by a pair of small denticles. Petiolar spines slightly shorter than the petiole, thin, pointed backwards and originating from the beginning of the petiolar sides. Postpetiole broader than petiole, with thin, pointed spines arising anterolaterally and curved backwards. Postpetiolar dorsum gently pointed dorsally.

Gaster oval, with an antero lateral crest not surpassing the first gastral stigma backwards.

Mid and hind femora angulate; mid and hind basitarsi long and without flat and broad base.

Sculpture. Head dorsum superficially and minutely punctate, with foveae deep and broader than their interspaces, diminishing in size anteriorly. Frontal carinae superficially punctate and with sparse, faint foveae and few, thin, oblique rugosities. Ventral face of the head and sides of the mesosoma superficially punctate and with thick longitudinal striae, the striae less regular on the pleurae. Mesosoma superficially punctate, with thick, longitudinal striae, rarely irregular. Pedicel with the same sculpture as the mesosoma but more irregular and with few, irregular foveae.

First gastral tergite superficially and minutely reticulate, with thin, irregular, longitudinal rugosities. First sternite with longitudinal rugae on the sides and on the anterior half; posterior half of the first gastral sternite superficially punctate and shining.

Legs reticulate-punctate, with slightly shining anterior and posterior faces of the femora. Distal part of the outer face of the femora and outer face of tibiae covered by small, irregular, superficial foveae.

Pilosity. Body with five types of hairs: (1) appressed and thick originating from each fovea; many more similar but originating or not from foveae thinner and sparse on the mesosoma and on the pedicel, dense on the cheeks, on the mesopleurae, on the middle of the metapleurae, on the gaster, on the distal part of the outer face of the femora and on the outer face of tibiae; (2) slightly clubbed on the sides of the frontal carinae, of the mesosoma, of the pedicel, on the anterolateral border of the first tergite, and on the legs; (3) truncate and subdecumbent, as long as the clubbed ones, mixed with type (1) hairs, on the pedicel and on the gaster; (4) minute and thin on the first gastral sternite; (5) long and slightly pointed on the posterior border of the gastral sternites.

Colour. Dark brown. Frontal carinae, tibiae, tarsomeres, mesosomal and peduncular spines yellowish-orange. First gastral tergite with a pair of yellow, oval spots anterolaterally. Anterolateral crest of the first gastral tergite yellowish-transparent.

Measurements (in mm) and indices: TL 3.92-4.68; HL 0.96-1.12; HW 1.12-1.24; EL 0.28-0.31; PW 1.06-1.08; PeW 0.56-0.62; PpW 0.65-0.742; HBaL 0.40-0.44; HBaW 0.08-0.09; CI 110.7-116.7; PI 112.0-114.8; PPeI 174.2-178.6; PPpI 145.9-153.8; HBaI 20.0-20.4.

Soldier

Kempf (1958) - Total length 6.3 mm; maximum length of head 1.85 mm; maximum width of cephalic disc 1.86 mm; maximum length of thorax 1.68 mm; maximum width of thorax 1.71 mm. Black; the following fuscous ferruginous: mandibles, anterolateral portions of cephalic disc, tip of scape, tibiae, tarsi, tip of peduncular spines; anterolateral corners of gaster with a yellowish-brown spot.

Head subopaque, subquadrate, surmounted by a nearly circular, anterolaterally somewhat excavate, mesially slightly convex, posteriorly nearly flat disc, the borders of which are noticeably crenulate but distinctly upturned laterally, more noticeably crenulate but not upturned posteriorly. Median portion of posterior border of cephalic disc vestigially excised or truncate between the vestigial, scarcely noticeable, occipital denticles. Floor of disc scarcely visible when head is seen in profile. Borders of occipital lobes sharply marginate, the lateral border crenulate, visible from the side as a distinct carina which runs foreward and upward on the sides of head toward the upper border of eye, but fading out before reaching it. Floor of disc finely but superficially reticulate-punctate, with sparse, larger foveolae, the interval between the foveolae being usually as broad, or even much broader than, the diameter of the pits. Foveolae larger, slightly more crowded on the sides of head and occiput. Lower face of head very finely reticulate-punctate, very sparsely foveolate.

Thorax opaque, finely reticulate-punctate throughout. Anterior border convex mesially, slightly concave laterally. Anterior corner with a prominent tooth. Lateral border of pronotum subparallel, crenulate, in front of the transverse carina, straight, converging caudad behind the carina, the posterior corner separated by mesonotum by a deep and narrow excision. Transverse pronotal carina not conspicuously crenate, sharply marginate, moderately prominent, shallowly excised medially. Promesonotal suture vestigial. Lateral lobes of mesonotum obliquely truncate and marginate. Mesoepinotal suture impressed laterally, vestigial mesially. Anterior corner of basal face of epinotum subrectangular, vestigially denticulate, followed behind by a broader, triangular projecting lobe, the posterior corner at most slightly dentate, practically unarmed. Declivous face not excavate, its lateral borders submarginate. Foveolae on dorsum of thorax slightly larger, and more crowded than on head disc, densely crowded on posterior half of basal face of epinotum, where the integument becomes reticulate-rugose. Sides of thorax with occasional irregular rugosities and grooves. Fore coxae with vestigial, fine, oblique rugulae on apical half of the outer face.

Peduncular segments opaque. Foveolae very dense, and irregular in shape. Postpetiole broader than petiole, the latter on each side with a strong, obliquely reflexed spine, the spine itself not curved. Anterior face of petiole obliquely truncate, bearing on the upper marginate border two minute denticles. Postpetiole with conspicuously longer, rather delicate lateral processes, the tip of which is obliquely recurved caudad. Body of postpetiole, as seen in profile, convex, the deepest portion just a little behind the anterior border.

Gaster opaque, subovoid. Anterior border moderately excised mesially, very narrowly crested laterally. First tergite finely reticulate-punctate, with slightly larger, yet very fine, rugosities, which form a scarcely raised network between the slightly impressed piligerous punctures. First sternite with a smooth posteromedian area, which is shiny, the rest subopaque, finely reticulate-punctate, with very fine longitudinal rugosities on the sides.

Standing hair thick, obtuse on apex, around the rim of cephalic disc, up to the posterior border, on the lateral border of occipital lobes, on the anterior half of the border of pronotum, one or two on mesonotal lobes, tip of peduncular spines, and a few on the anterolateral gastral crests and along the posterior border of the gastral sternites and tergites, and sparsely on the posterior half of the first sternite. Decumbent hairs scalelike, silvery, canaliculate, rather short in all foveolae of the head, thorax and peduncle. Very conspicuous on mesopleura where they are largest. very fine and minute on the first gastral tergite. Rather dense on the extensor faces of femora and tibiae.

de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 5.72-6.44; HL 1.48-1.60; HW 1.64-1.80; EL 0.32-0.36; PW 1.56-1.76; PeW 0.72-0.76; PpW 0.84-0.92; HBaL 0.33-0.48; HBaW 0.11-0.12; CI 110.8-112.5; PI 102.3-105.1; PPeI 216.7-231.6; PPpI 185.7-191.3; HBaI 25.0-26.2.

Queen

Kempf (1958) - Total length 6.5-6.8 mm; maximum length of head 1.57-1.64 mm; maximum width of cephalic disc 1.46-1.50 mm; maximum length of thorax 1.89 mm; maximum width of thorax 1.43-1.50 mm. In general resembling the soldier, with the peculiarities of the caste.

Cephalic disc more elongate, the floor mostly convex, only the anterolateral portions being slightly excavated. Anterolateral borders of disc slightly raised. Posterior half of disc either trapezoidal or more or less rounded. Posterior pair of ocelli very close to the occipital border. Lower face of head with the foveolae slightly larger and denser, and occasional longitudinal grooves. Occipital lobes with scarcely crenate border, the posterior corner rounded. Anterior corner of thorax dentate, the tooth not very prominent. Transverse pronotal carina little raised, vestigial toward the lateral border of pronotum, shallowly excised mesially. Lateral border of basal face of epinotum with a triangular lobe, the posterior corner unarmed, the posterior border nearly straight and transverse. Scutum very sparsely foveolate, the pits being somewhat denser on pronotum and scutellum, very dense and crowded on basal face of epinotum. Declivous face not excavate, its lateral borders immarginate. Mesopleural tooth prominent. Fore coxae with oblique rather coarse rugosities toward apex, of outer side. Petiole with obliquely truncate anterior face, the upper border of which is sharply marginate, forming with the dorsal face, as seen in profile a subacute angle. Lateral tooth of petiole relatively strong and projecting. Postpetiole with the same, yet shorter, rather delicate, more or less straight, lateral processes as in soldier. In profile the dorsum of this segment forms an anterior steeply ascending face, and a posterior descending face, meeting at an acute angle, the deepest part of the segment being farther removed from the anterior border, nearly in the middle of the length of the segment. Gaster subcylindrical, dotted with pale-yellowish on the anterior corner, and bearing on each anterolateral lobe a very narrow thin crest. Wings nearly hyaline, the pterostigma almost black, the veins brown. Venation of fore wing normal, transverse cubital vein (or vein: r-m) present. Fore wing, when reflexed backwards extending well beyond the normally contracted gaster.”

Measurements (in mm) and indices: TL 6.56-7.08; HL 1.40-1.52; HW 1.40-1.52; EL 0.33-0.36; PW 1.32-1.40; PeW 0.68-0.72; PpW 0.84-0.88; HBaL 0.48-0.56; HBaW 0.11-0.13; CI 100.0; PI 106.1-109.1; PPeI 183.3-194.4; PPpI 150.0-159.1; HBaI 22.9-23.2.

Type Material

de Andrade and Baroni Urbani (1999) - Soldier and gyne. Type locality: intercepted by the U. S. Plant Quarantine inspectors in New Jersey on Epidendrum aromaticum imported from Guatemala. Type material: holotype soldier and 5 paratype gynes (Museu de Zoologia da Universidade de Sao Paulo), examined.

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 602, Combination in Cephalotes)
  • Hespenheide, H.A. 1986. Mimicry of ants of the genus Zacryptocerus. J. N. Y. Entomol. Soc. 94: 394-408 (page 395, Combination in Zacryptocerus)
  • Kempf, W. W. 1958a. New studies of the ant tribe Cephalotini (Hym. Formicidae). Stud. Entomol. (n.s.) 1: 1-168 (page 119, pl. 4, fig. 6; pl. 5, fig. 6; pl. 6, fig. 1 soldier, worker, queen described)