Cephalotes bimaculatus

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

Cephalotes bimaculatus P casent0900247.jpg

Cephalotes bimaculatus D casent0900247.jpg

Specimen Label

Synonyms

Nothing is known about the biology of Cephalotes bimaculatus.

Identification

Unique member of its own bimaculatus clade characterised among all other species of Cephalotes for the following combination of characters; worker: propodeum with a small pair of denticles, gaster only slightly protruding anteriorly and with one pair of gastral spots; soldier and gyne: body foveae dense and irregular, cephalic disc concave, head bicoloured and gaster with only one pair of coloured spots. (de Andrade and Baroni Urbani 1999)

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Neotropical Region: Mexico (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.

  • bimaculatus. Cryptocerus bimaculatus Smith, F. 1860c: 77, pl. 4, fig. 4 (q.) MEXICO. Combination in Paracryptocerus (Harnedia): Kempf, 1958a: 136; in Zacryptocerus: Hespenheide, 1986: 395; in Cephalotes: De Andrade & Baroni Urbani, 1999: 563. Senior synonym of aztecus: De Andrade & Baroni Urbani, 1999: 563.
  • aztecus. Cryptocerus aztecus Forel, 1901c: 125 (s.w.) MEXICO. Combination in Paracryptocerus (Harnedia): Kempf, 1958a: 109; in Zacryptocerus: Brandão, 1991: 384. Junior synonym of bimaculatus: De Andrade & Baroni Urbani, 1999: 563.

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

Description

Worker

Kempf (1958) for aztecus - Total length 3.8-4.0 mm; maximum length of head 1.03-1.07 mm; maximum length of thorax 1.11-1.14 mm. Black; the following ferruginous: mandibles, tip of scape, basal and apical funicular segments, edge of frontal carinae, tip of tibiae, tarsites; rest of frontal carinae dark testaceous and semitransparent; tip of femora brown; anterolateral corners of gaster with a light spot, varying from yellow to ferruginous.

Head subopaque, strongly depressed, subquadrate, yet the maximum length distinctly exceeding the interocular width. Lateral border of the frontal carinae subparallel, not visibly excised in front of eyes. Lateral border scarcely upturned above eyes. Occipital corners obliquely truncate, the posterior border sharply marginate, gently emarginate. Eyes small, their greatest diameter less than one fourth of maximum head length. Dorsum of head finely reticulate-punctate, the macro sculpture being in between foveolate and reticulate-rugose and foveolate, the pits rather crowded, not deeply impressed, their diameter exceeding the width of their intervals. Lower face very finely reticulate-punctate, and not very coarsely reticulate-rugose, the rugae forming elongate meshes.

Thorax opaque, strongly depressed, its anterior border strongly arched mesially, somewhat concave laterally. Scapular angle incorporate in the sharply marginate lateral borders of pronotum, which conspicuously converge caudad and bear in front a subacute tooth, in the middle a vestigial, very obtuse tooth, forming a rectangular tooth at the posterior corner. Mesonotum with a more or less rounded lobe on each side. Promesonotal suture vestigial or obsolete. Promesonotum scarcely convex, the posterior portion of the mesonotum sloping abruptly downward to the impressed mesoepinotal suture and the epinotum which lies at a somewhat lower level than the promesonotum, when seen in profile. Anterior corner of basal face of epinotum subrectangular, not toothlike, the lateral border sharply marginate, forming a blunt, broad, scarcely projecting angle. Declivous face somewhat differentiated from basal face, its lateral border marginate. Dorsum of thorax finely and sharply reticulate-punctate, with coarse anastomosing rugosities forming a network, in the meshes of which lie the squamiferous foveolae. Declivous face of epinotum and sides of thorax finely reticulate-punctate with sparse, longitudinal (horizontal) rugosities, anastomosing on the pleura.

Peduncular segments opaque, their dorsal sculpture as that on dorsum of thorax. Petiole narrower than postpetiole, its anterior face nearly perpendicularly truncate, its sides bearing a small tooth, pointing laterad. Postpetiole with longer, rather stout anterolateral processes, the tips of which point obliquely caudad. Dorsum rather flat, lacking longitudinal ridges.

Gaster elliptical, opaque, strongly depressed, gently emarginate anteromesially, the anterolateral lobes broad, scarcely projecting, sharply marginate, lacking a transparent crest. The margination continues caudad along the lateral border, beyond the anterior half of the first tergite, which is finely reticulate-punctate, with rather fine, mostly longitudinal, rugosities. The squamiferous points not impressed. First sternites smooth and shining discad, reticulate-punctate laterad with more prominent, longitudinal rugosities on the sides.

Standing hair, as usual, confined to mandibles and tip of gaster, and a few short, thick setae, projecting from the lateral border of head, above eyes. Squamiform hair in foveae of head, thorax and peduncle silvery, canaliculate, but short and rather small. Finer, simple, almost minute on gaster and legs.

de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 4.70-5.18; HL 1.12-1.20; HW 1.20-1.32; EL 0.32-0.34; PW 1.00-1.12; PeW 0.52-0.58; PpW 0.56-0.62; HBaL 0.40-0.44; HBaW 0.12; CI 103.4-110.0; PI 111.1-117.8; PPeI 192.3-193.1; PPpI 174.2-180.6; HBaI 27.2-30.0.

Soldier

Kempf (1958) for aztecus - Total length 5.1-6.3 mm; maximum length of head 1.46-1.89 mm; of thorax 1.43-1.68 mm. Black; the following reddish-brown: mandibles, sides of head, occiput, pronotum in front of the transverse carina (rather infuscated), tip of femora, sides of tibiae, tarsites except the basitarsus; yellowish-brown: floor of cephalic disc, except for the anteromedian reddish-brown area, tip of scape, basal and apical funicular segments, extensor face of tibiae, and the two spots on the anterolateral lobes of gaster.

Head rather shiny, surmounted by an elliptical, elongate, excavate disc, the sides of which are strongly upturned all around, but scarcely crenulate. Floor of disc slightly raised anteromesially, just behind the vestigial clypeal area, the lateral and posterior portion of the disc excavate, not visible from the side, when head is seen in profile. Portion above frontal carinae semitransparent. Occipital lobes rectangular with their corner rounded, their borders strongly marginate posteriorly, vestigially marginate anteriorly, which in profile appears as an ascending ridge running forward toward the upper margin of eye, but fading out before reaching it. Lower border of cheeks marginate. Floor of disc and sides of head and occiput coarsely and strongly reticulate-rugose, forming more or less rounded meshes, which are deeply excavate, their bottom finely but only vestigially punctate, both ridges and pits are shining. Lower face of head with similar yet more superficial sculpture.

Thorax subopaque on dorsum, opaque on sides. Pronotum much broader than mesonotum, its anterior border gently arched, its anterolateral corner dentate, its lateral border strongly marginate, nearly straight evenly converging caudad, both in front and behind the slightly crested and raised transverse carina, which is not conspicuously interrupted mesially. Promesonotal suture present. Mesonotum on each side with a prominent, broadly truncate, oblique, strongly marginate lobe. Mesonotum flat. Mesoepinotal suture indicated by a depression in front of the transversely gently convex basal face of epinotum, the lateral border of which bears a triangular, broad little prominent projection, forming a blunt angle. Posterior angle of basal face unarmed. Declivous face of epinotum superficially reticulate-punctate, slightly excavate, somewhat shiny, its lateral border marginate. Dorsum of thorax with the same sculpture as on cephalic disc, but the bottom of the foveolae, circumscribed by the shiny ridges, is rather opaque, due to heavier microsculpture. Sides of thorax, including laterotergite, finely reticulate-punctate, irregularly rugose and reticulate-rugose. Squamiform foveolae sparse. Hind femora fusiform. Peduncolar segments and gaster as in worker, the former stouter, and the lateral processes slightly shorter. The lateral margination of the first gastral tergite is less distinct, likewise the longitudinal ridges on each side of the mesially smooth first gastral sternite. Conversely, the fine mostly longitudinal rugosities on first gastral tergite a little more prominent.

Standing hair as in worker, in addition a row of projecting, slightly clubbed setae, around the cephalic disc, excluding the posterior border, on the occipital lobes, on the sides of pronotum and a few on the tips of peduncular spines and the posterior border of the body of the postpetiole. Scalelike hair very prominent, rather long, silvery, decumbent, in the foveolae of head, thorax and peduncle, smaller on legs, minute on gaster.

de Andrade and Baroni Urbani (1999) - Measurements (in mm) and indices: TL 6.24-6.84; HL 1.60-1.76; HW 1.68-1.76; EL 0.36; PW 1.68-1.72; PeW 0.60-0.68; PpW 0.64-0.72; HBaL 0.42-0.44; HBaW 0.14-0.16; CI 100.0-105.08; PI 100.0-102.3; PPeI 252.9-280.0; PPpI 238.9-262.5; HBaI 33 .3-36.4.

Queen

de Andrade and Baroni Urbani (1999) - Head disc present. Posterior two thirds of the head dorsum slightly convex, anterior third moderately flat. Frontal carinae expanded anteriorly, converging posteriorly before the beginning of the eyes, connected by a convex carina on the vertex. Vertexal angles almost round and with crenulate margin. Eyes convex, not hidden by the disc in dorsal view. Clypeal border anteriorly concave. Mandibles with a lateral carina.

Mesosoma flat in side view. Humeral angles with an obtuse tooth anteriorly, straight posteriorly. Pronotal crest marked by a thin carina, superficially interrupted in the middle. Promesonotal suture impressed. Propodeum differentiated in basal and declivous face; basal face with slightly convex dorsum and sides, with a short, broad tooth in the middle of the sides and with a sulcus in the middle of the dorsum; declivous propodeal face with sides converging posteriorly and almost straight.

Petiole with differentiated anterior and posterior faces; anterior face declivous, posterior face moderately sloping backwards and with a small, broad denticle on each side. Postpetiole broadly convex, each side bears a broad tooth with obtuse tip arising anteriorly and prolonged backwards up to the middle of the postpetiole.

Gaster with protruding anterior border and with a superficial carina not reaching the stigma.

Legs. Fore coxae with anterior tumulus. Mid and hind femora without angle or denticles. Mid and hind basitarsi without broad base and compressed laterally.

Wings. Fore wings with R +Sc superficially reaching a marked pterostigma; 2r marked, Rsf5 connected with Rl; distal parts of A, Cu-Al and Mf4 vestigial. Hind wings with R, M+CuA, M and lA marked; CuA, M and distal part of lA vestigial.

Sculpture. Head, mesosoma and pedicel punctate and covered by deep foveae without interspaces between them on the head dorsum and more sparse on the anterior half of the pronotum. Ventral part of the head punctate, with anastomosing longitudinal rugosities alternated with foveae. Sides of mesosoma and legs deeply punctate, with few, almost longitudinal, rugosities on pro-, meso- and lower metapleural parts, on the distal part of the mid and hind femora and on the outer face of the tibiae. Gaster and posterior half of the declivous face of the propodeum punctate. First gastral tergite with anastomosing longitudinal rugosities on the first third, thinner on the last third. First gastral sternite with anastomosing rugosities on the anterior third and on the sides, shining on the middle. Few irregular rugosities on the meso- and metapleurae. Outer face of the tibiae with oval and superficial foveae.

Pilosity. Each fovea with an appressed canaliculate hair. Rim of cephalic disc with a fringe of moderately clavate hairs. The same type of hairs but sparser on the mesosoma, on the pedicel, on the legs and on the gaster, longer and less clavate on the apex of the gaster.

Colour. Dark brown to black. Frontal carinae reddish, outer face of tibiae, articulations between femora and tibiae and tarsomcres ferruginous. Anterior third of the first gastral tergite with an orange spot on each side.

Measurements (in mm) and indices: TL 8.32; HL 1.72; HW 1.68; EL 0.38; PW 1.72; PeW 0.72; PpW 0.82; HBaL 0.60; HBaW 0.18; CI 97.7; PI 97.7; PPeI 238.9; PPpl 209.7; HBal 30.0.

Type Material

Syntype Specimen Labels

de Andrade and Baroni Urbani (1999):

Gyne. Type locality: Mexico. Type material: holotype gyne labelled as such with the reference number 5970, without locality, in the The Natural History Museum, examined.

Cryptocerus aztecus. Worker and soldier. Type locality: Cuernavaca (Mexico). Type material: 5 soldiers, 11 workers and 1 male from Cuernavaca (Mexico) in Musee d'Histoire Naturelle Genève, Naturhistorisches Museum Basel, Museum of Comparative Zoology, Museo Civico di Storia Naturale, Genoa, examined. Synonymy by R. R. Snelling, personal communication, confirmed by our examination of the type material.

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 303, Raised to species)
  • 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 136, Combination in Paracryptocerus (Harnedia))
  • Smith, F. 1860c. Descriptions of new genera and species of exotic Hymenoptera. J. Entomol. 1: 65-84 (page 77, pl. 4, fig. 4 queen described)