Cardiocondyla venustula

An native of the old world tropics that has spread into subtropical and tropical areas of North America, Central America and the Caribbean.

Identification
Seifert (2003) provides a key to the holarctic species of Cardiocondyla that includes this and other tropical tramp species.

Distribution
Cardiocondyla venustula belongs to the C. shuckardi species complex of which 6 species occur in the Ethiopian, W Palaearctic, and Malagasy faunal regions. The nominal population found in Puerto Rico and Florida is most probably an anthropogeneous introduction from Africa (Seifert 2003).

Distribution based on Regional Taxon Lists
Afrotropical Region: Mozambique, Namibia, Zimbabwe. Indo-Australian Region: Hawaii. Nearctic Region: United States. Neotropical Region: Barbados, Greater Antilles, Haiti, Honduras, Mexico, Puerto Rico.

Biology
Wilson (1959) reported the following about the natural history of Cardiocondyla venustula:

This species has been introduced by modern commerce into the West Indies and is probably native to some part of the Old World tropics. Wheeler (1908) in 1906 and the present author found it abundant in the lowlands of Puerto Rico, especially in urban and other cultivated areas near the shore.. The following generalizations are based on my observations, pertaining mostly to two colonies in urban Santurce.

As also noted by Wheeler, venustula colonies are small, in maturity containing probably no more than one or two hundred workers. Nests are built in open soil. Both Santurce nests were polydomous, with two or three entrances no farther than two meters apart. In each case most of the colony was concentrated in one of the subnests. Workers were often seen transporting brood and other adult workers between the subnests. In adult transport, the two ants face each other, and one grips the other by some part of the head (probably the mandibles) and swings it over its back; the transported worker assumes the "pupal" posture, with appendages tightly withdrawn. The nest entrances are circular or slit-shaped and large enough to accommodate only one or several ants at a time. Their appearance changes after each heavy rain, when excavation is renewed by the colony. Typically, the workers pile a circle of miscellaneous debris around the entrance holes. For example, the following particles were, recorded around one chief entrance: dessicated fragments of Pheidole workers, small beetle elytron, unidentified piece of dry vegetable detritus, small tuft of cotton fibers. With each heavy rain the debris circle is washed away, but it is replaced within a few hours by the ants.

Foraging is most intense during the middle hours of the day, from late morning to middle afternoon. The workers seem to be most active in hot sunshine. As many as 23 were counted outside the larger of the two nests at peak activity. Workers hunt singly and range widely from the nest; a few were encountered as far as six meters away. Orientation is apparently visual; workers were frequently seen moving in nearly straight lines or considerable distances to and from the nests, and these could not be significantly disoriented by raking up soil in front of them. Venustula is principally, if not exclusively, a scavenger species. Following are records of food particles being brought to the nest by workers, made at random, during a period of several hours: 8 pieces of unidentifiable material, probably insect in origin (see below); one fragment of insect unidentified to group; 4 body parts of another ant species, identified in 3 cases to Pheidole; 2 small beetles; one small spider; one cicadellid. In every case the insect material was either dried or, if fresh, crushed or mangled, obviously having been found in an inactive state by the venustula workers. No evidence of predation could be found. Workers were observed on many occasions to start away from the numerous small spiders, collembolans, cicadellids and other insects that swarmed in the nest vicinity. On the other hand, they readily accepted dead insects offered them. Insects too large to be carried back by a single worker were carved into manageable pieces by the foragers. The great majority of food particles brought to the nest ranged in size from slightly less than the volume of a venustula worker head to about three times this size. Workers also accepted sucrose solution readily.

Wheeler's (1908) remarks about his 1906 observations of this species in Puerto Rico include the following: C. venustula is not uncommon in sandy and gravelly places, especially on the sea-beaches, where it lives in small colonies, comprising a single dealated queen and a few dozen workers, in shallow nests like those of some species of Leptothorax. It was found in Culebra in the same stations as Cardiocondyla emeryi. At Coamo Springs a few winged females were captured March 23, while they were issuing from a nest in a gravelly creek bottom.

Tandem Running
Some of Wilson's (1959) account of this behavior in Cardiocondyla venustula (see the tandem running page for more about this behavior):

Workers of this species were never seen to lay or follow odor trails. Instead, a distinctive form of communication is employed during foraging that involves, in most cases, only two workers at a time. The leader moves outward from the nest, with a single follower close behind. The communication is as follows: the leader remains perfectly still until touched on the abdomen by the follower ant. Then it runs forward for a distance of approximately 3 to 10 mm (or one to several times its own body length), only to come to a complete halt again. The follower ant is in a highly excited state, apparently stimulated by a secretion released by the leader; other workers approaching the leader become similarly excited, even when the latter is completely immobile at the time. After each contact and subsequent "drive" of the leader forward, the follower may press immediately behind and drive it again. More commonly, it circles widely about in a hurried movement that usually lasts for several seconds and may take it as far as a centimeter from the path set by the leader. In short time, however, the circling brings the follower once again into contact with the leader. If it touches the leader on the’ head or from the side, the latter does not move. In such cases the follower’ invariably moves around to the rear of the leader, touches it on the abdomen and starts it torward again.

In the great majority of cases, tandem running involved only two workers. Occasionally a third worker crowded in closely behind the leader worker but did not continue following for more than a few centimeters. Additional workers became excited by the leader only when they encountered it directly. There was no evidence of any kind of an odor trail.

A total of 16 tandem trips away from the larger venustula nest were followed to completion. Two of these were abortive, breaking off less than 15 centimeters from the nest. Seven led outward for distances of approximately one to two meters from the nest, in four cases to food baits set at this distance. The remaining seven led for three to five meters before breaking up or ending at a food source, a very considerable distance for so small an ant. All of the movements formed a nearly straight line, with only occasional, momentary doubling back. Eleven of the tandem runs ended without achieving any obvious goal. Five, however, ended at food sources, either dead insects occurring naturally or baits set by the author and both workers thereafter commenced feeding.

Although tandem running is apparently devoted in part or entirely to the communication of food finds, it is employed only by a fraction of workers engaged in successful foraging. Less than 10% of workers running from the nest to food masses were coupled in tandem pairs.

Nomenclature

 *  venustula. Cardiocondyla venustula Wheeler, W.M. 1908a: 128, pl. 11, fig. 5 (w.q.) PUERTO RICO. Senior synonym of badonei, globinodis: Seifert, 2003a: 257. See also: Smith, M.R. 1944a: 37.
 * globinodis. Cardiocondyla globinodis Stitz, 1923: 154 (w.) NAMIBIA. Junior synonym of shuckardi: Bolton, 1982: 316; of venustula: Seifert, 2003a: 257.
 * badonei. Cardiocondyla badonei Arnold, 1926: 225, fig. 64 (w.) MOZAMBIQUE. Subspecies of shuckardi: Santschi, 1932a: 387. Junior synonym of shuckardi: Bolton, 1982: 316; of venustula: Seifert, 2003a: 257.

Worker
2;-2-25 mm.

Head longer than broad, as broad in front as behind, with faintly convex, subparallel sides and nearly straight posterior border. Mandibles rather narrow, 6-toothed. Clypeus convex in the middle behind, with straight anterior border. Frontal area small, triangular, elongated. Antennal scapes not reaching the posterior corners of the head by a distance somewhat greater than their largest transverse diameter. Second and seventh funicular joints as long as broad; joints 3-6 broader than long; terminal joint longer and larger than the two preceding unequal joints together. Thorax slender, with rounded, sloping humeri and pronounced mesoepinotal constriction. Epinotum with two rather blunt teeth, which are as long as broad at their bases; basal surface slightly convex, nearly twice as long as the concave declivity. Petiole slender, node from above spherical, as long as broad and as long as the slender peduncle, into which it narrows rather abruptly. Postpetiole only 1 ½ times as long as the petiole and barely half as broad as the first gastric segment, but little broader than long, transversely elliptical; in profile distinctly lower than the petiolar node. Gaster elongate elliptical, somewhat flattened above. Legs slender.

Mandibles obscurely and sparsely punctate. Clypeus and frontal area somewhat shining, the former indistinctly, longitudinally rugulose. Head opaque, finely and regularly reticulate-rugulose. Thorax and post-petiole opaque, finely and densely punctate on the sides and below, above somewhat shining, with smaller punctures; petiole still smoother and more shining throughout, with distinct and very small punctures above. Gaster glabrous, with minute scattered punctures. Legs somewhat shining.

Appressed pubescence covering the body and appendages grayish, somewhat longer and sparser on the gaster. Hairs very few, confined to the anterior border of the clypeus.

Dark reddish brown; head and gaster nearly black; mandibles, antennal scapes and legs more yellowish; funiculi and the greater portion of the femora and tibiae, especially of the posterior legs, and the nodes of petiole and postpetiole, infuscated.

Seifert (2003) also provided a description of the worker - Head moderately elongated, CL/CW 1.185. Anterior clypeal margin between levels of frontal carinae usually slightly concave. Median occipital margin usually slightly excavated. Postocular distance large, PoOc 0.454. Scape long, SL/CS 0.842. Eye rather small,0.228. Frontal carinae immediately caudal of FRS level slightly converging or parallel. Paramedian area of vertex strongly reticulate (in the C. globinodis type reticulate-rugulose), meshes having 16 - 20 µm inner diameter and showing flat central tubercle of 8 - 9 µm diameter. Anteromedian area of vertex and frontal laminae strongly longitudinally carinulate; caudal area of clypeus finely carinulate-rugulose. Anterior area of clypeus with 5 - 10 longitudinal curved carinulae. In Caribbean population and the C. globinodis type pronotum dorso frontally finely transversally rugulose-reticulate, dorsal area of pronotum moderately shining but clearly microreticulate-microrugulose; dorsal area of propodeum mildly shining but regularly reticulate; lateral area of pronotum, and meso- and metapleurae finely to strongly reticulate, region of metapleural gland bulla with 3 - 4 weak longitudinal rugae. In specimens of SE African population whole mesosoma frequently strongly microreticulate, though small smooth patches may occur. Spines reduced to blunt obtusely-angled dents, interspinal area shining, very delicately microreticulate-rugulose. Metanotal groove deep but with shallow slopes. Petiole and postpetiole more or less shining but very finely reticulate-rugulose. Petiolar node in dorsal view nearly as wide as long and almost globular, in lateral view with rounded dorsal profile which slightly produced caudad in some SE African specimens. Anterior margin of postpetiole in dorsal view slightly concave, its sides convex. Ventral area of postpetiole with indication of 2 paramedian curved carinae. Gastral pubescence long and rather dense. Whole ant dark brown. For morphometric data of 24 workers see Tab. 10.

Queen
Length 2.75-3 mm.

Resembling the worker. Thorax narrower than the head, more than twice as long as broad, somewhat flattened above. Epinotal teeth stronger than those of the worker but of the same shape. Petiole and postpetiole of the same shape and proportions.

Head, thorax and postpetiole opaque above; petiole slightly more shining; all of these parts uniformly reticulate-rugose; the mesonotum behind with more longitudinal rugae; epinotal declivity smooth and shining.

Pubescence as in the worker. Wings minutely hairy, with a long marginal fringe on the posterior pair.

Head, thorax and nodes of petiole uniformly dark brown; gaster black, except the bases of segments 2-4, which are yellowish. Mandibles, legs and antennae of the same color as in the worker. Wings white, with colorless veins and stigma.

Seifert (2003) also provided a description of the queen - Head moderately elongated, CL/CW 1.182. Anterior clypeal margin between levels of frontal carinae usually slightly concave. Median occipital margin usually slightly excavated. Postocular distance large, PoOc 0.441. Scape long, SL/CS 0.815. Frontal carinae immediately posterior of FRS level slightly converging or parallel. Vertex strongly reticulate, in centre of meshes with flat tubercle; anteromedian vertex, frontal laminae, and clypeus strongly carinulate. Dorsal area of pronotum, whole mesonotum and scutellum, dorsal area of propodeum, postpetiole, and dorsal area of petiole strongly reticulate; mesonotum and scutellum with few superimposed longitudinal rugulae. Interspinal area smooth. Lateral area of petiole shining but finely reticulate. Lateral area of mesosoma reticulate, but finer than on dorsal area of mesosoma. Metapleuron longitudinally rugulose, more coarse and upcurved in region of metapleural gland bulla. Spines reduced to short dents. Petiolar node in dorsal view slightly wider than long, in lateral view semicircular and slightly produced caudad. Anterior margin of postpetiole in dorsal view concave, its sides angulate-convex. Anteroventral area of postpetiole with 2 suggested paramedian, curved carinae (or longitudinal bulbs). Whole body with profuse and subdecumbent pubescence. Dark to medium brown. For morphometric data of 4 gynes see Tab. 18.

Type Material
Seifert (2003) lists the following type material that he examined:

Cardiocondyla venustula: lectotype worker (by present designation, in NHM Los Angeles) and 5 paralectotype workers labelled "Coamo Springs Porto Rico W.M. Wheeler", NHM Los Angeles and SMN Görlitz. 7 paralectotype workers labelled "Culebra I. W.M. Wheeler.", NHM Los Angeles and SMN Görlitz.

C. globinodis: 1 type worker labelled "Deutseh-Sw.-Afr. Omaruru 21.-22.6.1911", "Hamb. Dtsch.-sw.afr.Studienr.1911 W. Michaelsen leg.", and "Cardiocondyla globinodis Stz", ZM Berlin.

C. badonei: 1 syntype worker labelled "Amatongas forest P.E.A. -2.1917 Nat Museum S. Rhodesia", "M.C.Z. Paratype 29057", "Cardiocondyla shuckardi For. r. badonei Arn. det. G. Arnold 1953", MCZ Cambridge. 2 syntype workers labelled "Cardiocondyla shuckardi For st. badonei Ar" \"Port. East Afr. Amatongas forest IX 17" \ "Type", NHM Basel.

Additional References

 * Wilson, E. O. 1959. Communication by Tandem Running in the Ant Genus Cardiocondyla. Psyche. 66:29-34. DOI:10.1155/1959/29093