Karavaievia

Asian Weaving Carpenter Ants

Diagnosis. Emery (1925): "Worker. - No caste polymorphism. Head round with rounded sides; anterior clypeal margin more-or-less rectilinear, posterior margin somewhat concave. Eyes situated anterior to posterior third of lateral head margin. Clypeus short and depressed, without median carina; anterior clypeal margin weakly sharpened laterally sides, straight or slightly sinuous medially; lateral clypeal portions very small, occupied almost entirely by the clypeal fossae. Frontal carinae short and not sinuous. Mandibles short and strongly curved along lateral margins, and armed with 5 teeth. Mandibles somewhat long. Scapes surpassing posterior head margin in repose; pedicel longer than antennomere 3. Mesosoma slender; constricted in middle as seen in dorsal view; in profile, mesosomal dorsum strongly impressed anterior to propodeum and, at bottom of impression, metanotal spriracles protrude from the profile. Sutures between mesonotum, metanotum, and propodeum erased. Petiolar scale vertical with sharp edges. Queen.- Head more elongate than that of worker, with straighter lateral margins; rest of head similar to worker. Anterior clypeal margin impressed or excised medially. Male. - (From Viehmeyer.) Head somewhat wider than long, with big and strongly convex eyes. Anterior clypeal margin linear. Mandibles with strong apical tooth.

Geographical distribution of species. - Malaysia."

(Translated by B. E. Boudinot, 17 February 2017.)

Karavaievia is currently a subgenus of Camponotus.

Identification
Dumpert (1996) - The subgenus Karavaievia is a very well defined taxonomic unit containing not only morphological but also behavioural characteristics. The common morphological traits include the subuniform size of workers, females and males, the shape of the head, the position of the eyes, the characteristic shape of frontal carinae, clypeus, mandibles, antennae and alitrunk. Camponotus (Karavaievia) orinus showed deviations by the slight polymorphism of the worker caste. Though the six presently described species fit quite well in this subgenus, there are some minor differences in a species to the rest of the Karavaievia species. This contains the relatively small length of the Camponotus micragyne females and the shape of the workers and females of Camponotus striatipes. Heads, gaster and especially alitrunks of these species are much thinner and distinctly more slender than found in all other Karavaievia species. Also the excision of the anterior clypeal margin of the C.  striatipes females differs in shape and extension from the very uniform clypeal shapes of the females in all other Karavaievia species.

On the other hand, there is no doubt that these species all belong to the Camponotus subgenus Karavaievia. All the other characteristics of Karavaievia fit quite well including a lacking of worker polymorphism to a large extent. The main characteristic of Karavaievia, however, seems to be the weaving of silk nests with the aid of their larvae.

Biology
Dumpert (1996) - In 1984 we discovered in Peninsular Malaysia near the Ulu Gombak Field Studies Centre of the University of Malaya an Old World silk weaving Camponotus species, Camponotus texens. It produces silk carton nests mainly beneath leaves of trees, which contain brood as well as trophobiotic Homoptera symbionts. This species turned out to belong to the subgenus Karavaievia from which two species and one subspecies were described from Singapore and Borneo. Since then we discovered eleven further species, of which six had been described. All are weaver ants which produce silk carton nests. As Camponotus (Karavaievia) dolichoderoides overbecki discovered by Viehmeyer (1915) was also found in carton pavilions we can suppose that the whole subgenus is silk weaving. The majority of the species were found on Peninsular Malaysia possibly due to more thorough collection. Most of the species were found in primary forests, two in the Pasoh Forest Reserve and three in Belum during the Expedition of the Malaysian Nature Society in 1994. In some cases, only one colony or a few pavilions could be found. We do not know whether Karavaievia species are very rare or are only seldom found because of their canopy dwelling life habits.

Dumpert et al. (2006) - Natural preformed nesting sites are rather limited in the canopy region of the tropical rainforest. By constructing free-hanging nests in this habitat, weaver ants get access to the leaf and crown region. In these ants silk of the larval labial glands is not only used by the mature larvae themselves for spinning their pupal cocoon but also for nest construction. Like weaver shuttles worker ants take large larvae with their mandibles and use the silk secreted by them to spin together leaves or to form flexible and firm carton nest walls out of particles with help of the fresh sticky silk.

Until recently four independent groups of weaver ants were known worldwide, all of them belonging to the subfamily Formicinae. Two are found in the Old World tropics (the famous genus Oecophylla Smith, 1860 and many species of the genus Polyrhachis Smith, 1857) and two in the New World tropics (species of the subgenera Dendromyrmex Emery, 1895 and Myrmobrachys Forel, 1912 of Camponotus Mayr, 1861) (Hölldobler & Wilson 1977, Schremmer 1979).

Nesting Biology
Dumpert (1996) - Karavaievia live arboreally, weaving silk nests with the aid of their larvae. Most of these nests are built at the undersides of leaves, forming free-hanging pockets. This holds for the vast majority of the pavilions of Camponotus melanus, Camponotus gentingensis, Camponotus belumensis, Camponotus nigripes, and Camponotus asli. In all these cases, the silken material at the outside of the pavilions is covered with particles. C. asli, C. gombaki, C. belumensis, C. micragyne and C. texens were shown weaving additional nests between leaves. C. striatipes pavilions were found in folded leaves that are woven together with the aid of larval silk. The pavilions of most of the newly described species (C. striatipes, C. melanus, C. gentingensis, C. belumensis, C. nigripes) consist of merely one chamber like those of C. asli and C. texens. Only the pavilions of C. micragyne were found to consist of more than one chamber like those of C. gombaki and especially those of C. orinus. Nearly all hitherto investigated Karavaievia species contain in at least most of their pavilions scale insects as trophobionts. This is valid for C. texens, C. gombaki, C. asli, C. orinus, C. melanus, C. belumensis, C. gentingensis, and C. nigripes. Only the few (3) pavilions that were found as well of C. micragyne as of C. striatipes contained no trophobionts. Pavilions of C. belumensis were found to be fully packed with pupae of this species.

Concerning the vertical distribution of the Karavaievia species, the few findings do not justify any conclusions. The C. texens colonies and those of C. gombaki, C. asli, C. melanus, C. belumensis and C. orinus were found on small trees (2-5 m in height). The findings of C. striatipes were made in heights of about 30 m, and those of C. gentingensis, C. micragyne, and C. nigripes were made on fallen branches. This means that Karavaievia spp. at most are canopy dwelling ants. So it is impossible to say, whether or not the crown regions of the rain forest trees contain Karavaievia colonies in a larger scale. From the fact, however, that the recent Karavaievia findings revealed more new colonies than of already known species, one can conclude that the number of species in this subgenus is probably still considerably higher than already known. The discovery of 12 new species (including a yet undescribed species already mentioned in the accompanying key) in addition to the 2 formerly known in this ant taxon demonstrates very convincingly how diverse rain forest canopy fauna can be and how little is known about it.

Life conditions and geographic distribution of Karavaievia
Dumpert et al. (2006) - In the evergreen rainforest zone of Southeast Asia most of the woody plants possess leaves that persist over several years and are not shed synchronously (Whitmore 1988). Only this type of leaf is suited as a substrate for the long-lasting nest pavilions built by Karavaievia. All known Karavaievia species nest in this way. Moreover Karavaievia workers are able to recognize in advance the moment of natural shedding of inividual leaves, possibly through the change of honey dew production of their trophobionts on the decaying leaves within the pavilions (Waldkircher and Maschwitz 2002). Consequently, without any loss of colony members such pavilions can be abandoned in time and their brood and trophobionts can be transported to other leaf nests before leaf drop. Synchronous annual defoliation, however, as commonly occurring in woody plants of the monsoon zone during the dry season would simultaneously destroy the numerous pavilions of a Karavaievia colony on such a plant, i.e., its whole nesting and trophic base.

Correspondingly, most, i.e., 15 of the known 18 Karavaievia species were found in the evergreen rainforest region of Sundaland, i.e., Borneo, Peninsular Malaysia, Sumatra and Mentawei island (Dumpert et al. 1995). Many of these have been found only once or twice. Only Karavaievia texens was found frequently, within a large area ranging from the east coast of Peninsular Malaysia to West Sumatra (Dumpert et al. 1995 and unpubl.). We suppose that many more species remain undiscovered in the vast unexplored regions of ever wet Sundaland: no collections exist from the moist regions of Java, from large parts of Borneo and Sumatra and from many smaller islands. As Karavaievia is neither specialized in living on specific plant species nor in cultivating specific trophobionts and as colony founding queens are able to disperse over water by flight, no limitations by the classical biogeographic Sundaland distribution borders, e.g., such as Wallace's Line, have to be expected (Whitmore 1988). Thus Karavaievia should also be looked for on Sulawesi and on the Philippines.

Colony foundation, rareness and high species diversity in Karavaievia
Dumpert et al. (2006) - Most species of Karavaievia have only been collected once or twice indicating their rareness in their habitats. The supposition that colonies are abundant in the inaccessible upper forest canopy is not consistent with our long term observations. We often have found their colonies in lower and middle heights of the forest. Additionally the crowns of hundreds of larger fallen trees checked over many years in our observation area in the Gombak valley/Peninsular Malaysia never were inhabited by any Karavaievia colonies. Here in a quantitative counting during a road side clearing action 312 fallen trees up to 12 m height were checked for ants: 12 % of them were occupied by weaver ants (Oecophylla or Polyrhachis spp.) and 6 % contained carton nests of various ants, but none was inhabited by any Karavaievia. During extensive research on nest building behavior, nest architecture and details of nest materials (silk, diverse plant material [carton-nest], and minerals), in tropical canopy-dwelling Formicidae we found clear indication not only for genus specific but even species specific nest constructions (Weissflog 2001). Thus, the majority of free-hanging canopy nests can be assigned to species even without seeing the original inhabitants. An important reason for the rareness might be the mode of colony foundation of Karavaievia species as described here. The typical mode of colony foundation in Karavaievia seems haplometrotic (a single queen establishes a new colony). Because colony-founding queens are not able to build pavilions without silk of last stage larvae, they cannot form any foundation pavilions under free hanging plant leaves. Instead, in at least two species, such queens used as foundation chambers abandoned or weakly colonized leaf nests of other pavilion building canopy ants which still contained trophobionts. We found colony founding queens of Karavaievia in nests of Monomorium species (Myrmicinae) which are able to construct their leaf pavilions without silk. This hitherto unknown mode of colony foundation has been found so far in C. (K.) schoedli from Thailand and in C. melanus from Borneo. In the cases of Camponotus schoedli and Camponotus melanus the colony founding queen was detected with her own brood and trophobiotic partners inside a single Monomorium sp. nest pavilion, while workers of Monomorium nested in the neighborhood on the same tree in separate pavilions.

A large colony of Camponotus micragyne from Sumatra mainly inhabited species specific self-constructed pavilions. However, it also had fully taken over some of the typical pavilions of a canopy dwelling Monomorium. Some Monomorium sp. pavilions were inhabited by C. micragyne and by Monomorium sp. at the same time.

This observation indicates that also in this species colony foundation may happen in a similar way to that of C. schoedli and C. melanus.

A similar mode of colony foundation is known from one type of true social parasites, the “temporary social parasites”. They have developed a high species diversity in temperate zones but are lacking in the tropics. Like Karavaievia, they are rare compared to their host species. Like Karavaievia temporary social parasites penetrate into the colonies of their hosts. However true social parasites are different in that they take over not only the nest building but also workers and brood of the host ant colony after having killed its queen. Phylogenetically, true social parasites appear to have evolved directly from their host species or from closely related ancestors. This is the so-called “Emery's Rule” (Emery 1909).

We do not know whether the Karavaievia queens kill the Monomorium sp. individuals during the take-over of the Monomorium nest pavilions. Nevertheless such a take-over can be classified as a mild sort of interspecific parasitism. However, we do not know whether Karavaievia also take over abandoned pavilions of Monomorium sp. or nests of other pavilion building canopy ants. Thus questions about whether these relationships are obligate or facultative and whether it is specific or non specific nest founding parasitism, remain open. At present, we can only suppose that the take over of trophobionts is obligate.

More common SE Asian canopy weaver ants like Oecophylla smaragdina (Fabricius, 1775) or various Polyrhachis species need no preformed pavilions and no trophobionts for colony foundation (Dorow and Maschwitz 1990, Liefke et al. 1998, Buschinger 2001, Weissflog 2001).

Species

 * Camponotus asli
 * Camponotus aureus
 * Camponotus belumensis
 * Camponotus dolichoderoides
 * Camponotus exsectus
 * Camponotus gentingensis
 * Camponotus gombaki
 * Camponotus khaosokensis
 * Camponotus maschwitzi
 * Camponotus melanus
 * Camponotus micragyne
 * Camponotus nigripes
 * Camponotus orinus
 * Camponotus overbecki
 * Camponotus schoedli
 * Camponotus striatipes
 * Camponotus texens
 * Camponotus weissflogi

Nomenclature

 *  KARAVAIEVIA [subgenus of Camponotus]
 * Karavaievia Emery, 1925b: 115 [as subgenus of Camponotus]. Type-species: Camponotus exsectus, by original designation.