Carebara

Worker minute, monomorphic, yellow, without eyes or ocelli; antennae 9- jointed, joints 2 to 6 very small, the two terminal joints forming a large and distinct club, with very long last joint. Mandibles with oblique 3- or 4-toothed apical margins. Frontal carinae short; frontal groove and frontal area absent. Clypeus simple, unarmed, without carinae. Epinotum unarmed. Petiole with a short peduncle, its node higher and larger than that of the postpetiole; both nodes from above transverse, subelliptical.

Female enormously larger than the worker, dark-colored, with well-developed eyes and ocelli. Antennae short, 10-jointed, the funiculi without a distinct club, their joints 2 to 5 not much narrower than the remaining joints. Thorax large and robust, convex above, higher than the head, the mesonotum anteriorly more or less overarching the small pronotum, with well-developed parapsidal furrows. Epinotum unarmed, or with low flattened lobes or protuberances on the sides. Tarsi densely clothed with short, stiff bristles. Wings large, the anterior pair rather pointed, with one cubital, a discoidal, and a closed radial cell and a well-developed pterostigma.

Male somewhat smaller than the female, but similarly colored, with long, 13- jointed antennae, scapes short, first funicular joint not swollen nor globular, remaining joints long and cylindrical. Mesonotum large, without Mavrian furrows. Nodes of petiole and postpetiole only feebly developed.

The genus Carebara (Map 24) is represented by seven species in the Ethiopian and two in the Indochinese Region ( C. lignata Westwood and C. castanea F. Smith ). Santschi described some females and males taken in French Guiana as Carebara carinata .1 The former measure 12 to 12.8 mm., the latter 9.3 mm. He is of the opinion that the species hitherto referred to the Neotropical genus Tranopelta , originally founded by Mayr on male specimens, are also to be referred to Carebara . Forel, however, in his description of the workers of T. gilva Mayr variety brunnea shows that. Mayr's genus is perfectly distinct. These workers are somewhat dimorphic, have eyes, and both the workers and females have 11-jointed antennae, with a 3-jointed clava. The male alone is very similar to Carebara , especially to the male of C. osborni described below. These characters are all evident in a series of worker, male and female cotypes of brunnea in my collection. Emery 2 had previously based another Neotropical genus, Carebarella , on females and males of a species ( C. bicolor ) from Brazil and Peru. He also described a worker from Ega, Brazil, under the name Oligomyrmex anophthalmus .

At first sight the occurrence of species of Carebara and Oligomyrmex in South America seems veiy doubtful. During a recent trip to British Guiana I was able to secure all three phases of a new subspecies of Santschi's C. carinata and of the typical form of Tranopelta gilva . The worker of the former shows that it is without a doubt a true Carebara ,and Prof. Emery, to whom I sent specimens for comparison with his Oligomyrmex anophthalmus , writes me that the latter, though specifically distinct, belongs to the same genus. It should therefore be known as Carebara anophthalma . The new subspecies of carinata was taken in a large termitarium of Syntermes dirus Klug, and it is interesting to note that of all the Neotropical termites this is most like the large Termes species with which the Ethiopian Carebarae live (vide infra). I took Tranopelta gilva , however, in the deeper parts of the nest of the large ponerine, Paraponera clavata (Fabricius) , and also living independently with coccids under bark.

Emery has placed Tranopelta and Carebarella with Diplomorium and Solenopsis in the tribe Solenopsidini and has made a tribe Pheidologetini for the genera Pheidologeton , Aneleus, Lecanomyrma, Oligomyrmex (including the subgenera Aeromyrma and Octella), Erebomyrma, Psedalgus, and Carebara . It would seem to be more natural to include all these forms in the single tribe Solenopsidini. Evidently Carebara , in the diminution of the antennal joints and the loss of the eyes in the worker, in the secondary reduction of this caste to monomorphism, and the secondary enormous enlargement of the females and males, represents the most extreme development of the whole series of genera, which probably started from forms like the existing species of Pheidologeton . Since the volumes of bodies of the same shape vary as the cubes of their diameter, a female Carebara vidua measuring 24 mm. would be 4096 times as large as the cospecific worker, which measures only 1.5 mm., if the two insects were of the same shape. But the female is a much stouter insect in proportion to her length than the worker, so that she must be nearly 5000 times as large. And this disproportion occurs not only among individuals of the same species but of the same sex and among the offspring of the same mother! The only other insects which exhibit a like disproportion are the workers and physogastric queens of the very termites with which Carebara lives as a predatory parasite. The extraordinary differences in stature between the workers and sexual phases of Carebara are undoubtedly correlated with interesting habits of the species. Haviland1 was the first to show that C. vidua lives in the masonry of the large nests of Termes natalensis in Natal. He discovered the minute workers but was unable to elucidate the relations of the ants to the termites. Forel {loco citato), inferring from analogy with our northern cleptobiotic species of Solenopsis ( S. fugax , molesta , etc.) advanced the hypothesis that the Carebara colonies live in cavities of their own in the masonry of the termitaria and that these cavities are connected with the galleries of the termites by means of very tenuous passages through which the Carebara workers, but not the termites, can pass. The Carebara workers, probably remaining unnoticed on account of their small size, prey on the termites with impunity and are therefore able to rear such huge sexual forms. The larvae of these are so voluminous that they could not be moved by the workers and are so soft and vulnerable that they would have to be reared in chambers inaccessible to the termites. Although no detailed observations on the relations of the two species have been published, the subsequent accounts of observers in the field go to confirm Forel's inferences.

Bequaert1 has witnessed the marriage flight of Carebara junodi Forel. He says:

This species is remarkable on account of the extraordinary disproportion between the female and the workers. In the Katanga it lives in the mound-shaped nests of Acanthotermes spiniger. October 6, 1911, I witnessed at Sankisia a nuptial flight of this ant. It was at the very beginning of the rainy season and on the two preceding days it had rained abundantly. Toward noon numerous winged females were flying about everywhere in the savannah; they came from a certain number of termitaria, the sides of which were covered with fabulous numbers of the very small workers of the same species. I did not see copulation but, in the evening, I captured several males at light but no females. The following days the phenomenon was not repeated.

The huge Carebara females are, among the aborigines of the Congo, a muchsought-for delicacy. Hence they take advantage of the nuptial flight to collect a great number of individuals. The swollen portion of the abdomen alone is utilized. They eat it either roasted or raw.

Dr. Bequaert informs me that his attention was directed to the marriage flight described above by the excitement of the congregated natives who were actually filling pails with the torn-off gasters of the females. Each Carebara colony gave off hundreds of females and the number of workers that covered a termitarium during the flight must have run into the millions. The workers of Carebara , like those of other hypogseic ants (Erebomyrma, Acanthomyops , etc.), apparently come to the surface of the soil only while the nuptial flight is in progress.

Arnold2 adds the following interesting note to his description of Carebara vidua .

It is probable that the dense tufts of hairs on the tarsi of the female serve an important purpose - that of enabling some of the minute workers to attach.themselves to the body of the female when the latter is about to leave the parental nest. Several specimens of the female have been taken by me with one or more workers biting into the dorsal fimbriae. I am inclined to suspect that the young queen cannot start a new nest without the help of one or more of the workers from the old nest, on account of the size of her mouth-parts, which would probably be too large and clumsy to tend the tiny larvae of her first brood, and that it is therefore essential that she should have with her some workers which are able to feed the larvae by conveying to them the nourishment from the mouth of the queen.

I find that the workers also attach themselves to the tarsi of the males. Two specimens of this sex referable to C. vidua ., evidently taken at fight and sent me by Mr. C. C. Gowdey from Kampala, Uganda, each bear two workers firmly attached by their mandibles to the tarsal hairs. Such workers must, of course, perish with their carriers, unless they can manage to pass over to the legs of the females during copulation.

The workers and females of the African Carebarae can be separated by means of the following keys.

Females

1. Large species, more than 20 mm. long.......................................2.

Small species, not more than 15 mm. long................................4.

2. Mandibles with only 2 teeth and the remainder of their apical borders undulated, not properly dentate.................................. ampla Santschi .

Mandibles with more than 2 teeth, entire apical border dentate.............3.

3. Black; the gaster sometimes red; mesonotum about as broad as long; clypeal border not emarginate in the middle; hind metatarsi much shorter than

hind tibiae............................................ vidua F. Smith .

Dull rusty red; mesonotum with three dark brown longitudinal stripes; thorax narrower; clypeal border broadly emarginate in the middle; hind metatarsi but little shorter than the hind tibiae.................. junodi Forel.

4. Length 13 to 15 mm.; dark brown or castaneous..........................5.

Length only 8 mm.; paler and more reddish brown...... osborni , new species .

5. Body covered with short hairs; clypeus merely coarsely punctate.. sicheli Mayr . Body almost hairless; clypeus transversely rugulose in the middle. langi , new species .

Workers

1. Mandibles 3-toothed. Length 1.7 to 1.9 mm................. arnoldi (Forel).

Mandibles 4-toothed....................................................2.

2. Base of epinotum longer than the declivity, marginate on the sides. Length 1.6 to 2 mm........................................ vidua F. Smith .

Base of epinotum shorter...............................................3.

3. Petiolar node one-fourth narrower than the postpetiole. Length 1.5 to 1.8 mm. silvestrii Santschi .

Petiolar node as broad as the postpetiole..................................4.

4. Thorax not impressed at the mesoepinotal suture; promesonotum but slightly longer than broad; epinotum subcuboidal with subequal base and declivity. Length 0.8 to 1 mm............................... osborni , new species .

Thorax distinctly impressed at the mesoepinotal suture; promesonotum much longer than broad; epinotum not subcuboidal, its base very short, its declivity long and sloping. Length 1.7 to 1.9 mm......... junodi Forel.

Concepción (ALWC, MHNG).

Carebara , Westw. Ann. & Mag. Nat. Hist. vi. 86 (1841).

Head small, much narrower than the thorax; eyes ovate, placed high on the sides of the head; antennae short; the flagel- lum 9-jointed, the basal joint as long as the two following, the joints from the second, gradually increasing in length and thick- ness, not having a distinct club; mandibles short, stout, widen- ing to their apex, which is oblique and dentate; maxillary palpi 3-jointed, labial palpi 2-jointed. Thorax ovate, very convex above; wings ample, the anterior pair with one marginal, two submarginal and one discoidal cell; the intermediate and poste- rior tibiae destitute of spines at their apex, the anterior tibiae with a single calcar or spine. Abdomen very large, ovate, much wider than the thorax.

The above characters are those of the female, the workers are not known.

Carebara is a genus of ants in the subfamily Myrmicinae. It is one of the largest myrmicine genera with more than 200 species distributed worldwide in the tropics and the Afrotropical region. Many of them are very tiny cryptic soil and leaf-litter inhabitants. They nest in rotten wood to which the bark is still adherent in the Afrotropical region, or may be lestobiotic nesting near other ant species. Some species are known to exist parasitically within termite nests. Little is known about the biology of the genus, but they are notable for the vast difference in size between queens and workers.