Proatta butteli

The only species in its genus, Proatta butteli is found in southeast Asia and is strikingly similar in appearance to New World Attine species. Unlike the Attines, Proatta butteli is a predator and scavenger. Their prey includes isopods, centipedes and a variety of insects, including other ant species. Eguchi et al (2011) - Proatta butteli is found in lowland forests of southern Vietnam, and nests under stones and wood fragments and in soil around tree bases. Adults are brick red and dull and are clad in dirt. When their nests are exposed, the cryptic workers freeze for a while, making them very difficult to detect.

Identification
The combination of 11 antennal segements, size (~2 mm), the series of spines along the dorso-lateral margins of the mesosoma, and the conspicuous frontal carinae that extend from the frontal lobes to the occipital margin set these workers apart from other co-occurring Myrmicinae ant species. In general appearance they are most similar to a number of Attine genera, which are all found in the New World.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia. Oriental Region: Thailand, Vietnam.

Biology
Moffett (1987) - Proatta butteli workers scavenge for invertebrate remains and prey on live arthropods. The ants also collect bits of fresh or dried vegetations, wood, and other plant material and recruit to piles of sesame seeds provided near nest entrances. Apparently none of these plant materials are eaten, however, although they are added to the debris the ants let accumulate inside the nest.

Colonies of Proatta butteli are polygynous, with numerous queens present. There is no evidence for aggression between queens or differential treatment of queens by workers. Also, there is no sign of intraspecific aggression: the ants readily acceptted workers transplanted from distant sites.

Workers search for food solitarily, foraging only a short distance (invariably less than a meter) from each nest entrance. Within the limited foraging area worker density tends to be high, and clumps of as many as 50 foragers are sometimes present. This foraging pattern allows for rapid exploitation of discovered food. Recruitment occurs along odor trails formed from a pheromone originating in the poison gland.

In addition to small prey and scavenged arthropod corpses, the ants capture prey larger than themselves. Such prey are taken by an inchoate form of group predation. The first worker to encounter the prey attempts to restrain it. Because of the high forager density, additional workers soon arrive seemingly by chance and aid in pinning the prey in place. Unlike attine ants, Proatta butteli does not feed on fungi.

Although workers vary little in head width (0.51 to 0.70 mm), they show a modest division of labor by size, with smaller individuals being relatively numerous in the brood area.

Nesting Biology
Most nests are near tree bases. Colonies infiltrate rotten roots, abandoned termite nests, and other cavities near the surface, forming within them a labyrinth of chambers and galleries. The ants apparently make use of available spaces, with little additional excavation. The chamber surfaces are lined with detritus such as woody frass and prey' remains. Dealate queens are numerous, with roughly one queen for every 100-500 workers throughout the nest. Nest entrances are scattered on the ground above the chambers, and are unornamented except for strewn debris. The primary study colony is one of the largest I have seen, probably containing several thousand ants, and possibly 10,000 or more. The nest site has been occupied for at least 3 years.

Nomenclature

 *  butteli. Proatta butteli Forel, 1912m: 769 (w.m.) INDONESIA (Sumatra). Crawley, 1924: 401 (q.); Wheeler, G.C. & Wheeler, J. 1986b: 447 (l.). [Also described as new by Forel, 1913k: 86.] See also: Moffett, 1987: 444.

Worker
Environ 2mm, 5. Caracteres du genre (see below). Glabre. Pattes un peu pubescentes, sans poils dresses. Les epines epinotales (derriere) un peu courbees et un peu plus courtes que l'epinotum. Mate, abdomen lisse. Les pattes, comme les antennes, ont tout a fait l'aspect de celles des Atta. D'un roussatre clair. Milieu de l'abdomen un peu brunatre.

(as given for the genus) Aspect tout semblable a une Atta, specialement au sousgenre Mycocepurus For., avec cette difference fondamentale, que les antennes ont 12 articles au lieu de 11. Les antennes forment la meme massue; les mandibules, en triangle allonge, ont deux dents devant et des denticules derriere. L'epistome a une carene laterale a l'oeil, et, comme chez certains Cyphomyrmex, un lobe median eleve et deprime au milieu. Les arêtes frontales sont prolongees a peu pres parallelement jusqu'a l'occiput. De meme, une carene posterieure se prolonge aussi jusqu'a l'occiput qui est ensuite tronque et termine par deux dents; une troisieme dent mediane terminant les aretes frontales. Toutes ces dents un peu courbees en avant. La tete est mate, reticulee-ridee en long. Elle est plus longue que large, a cotes peu convexes, echancree derriere; les aretes frontales sont retrecies et comme un peu liees entre elles au milieu. Les yeux sont situes presqu'au milieu et globuleux. Le pronotum et le mesonotum portent d'abord trois paires d'epines, la premiere est la plus ecartee, la troisieme la moins ecartee, toutes un peu courbees en avant. Puis une quatrieme paire, plus rapprochee, entre les epines pronotales. En arriere du mesonotum, il y a encore une epine mediane impaire, mais plate et bifurquee. L'epinotum porte d'abord, en avant, une epine impaire unique au milieu, puis, en arriere, la paire d'epines ordinaires recourbees en arriere et assez longues. Le pedicule a un petiole median et un noeud posterieur surmonte de quatre dents, impressionne au milieu, un peu plus long que large. Le second noeud est transversal-arrondi, plus de deux fois plus large que le premier, notablement plus large que long. Mate, irregulierement recticulee sur un fond plus ou moins granule. L'abdomen seul est luisant. Toutes les epines sont a peu pres de meme grandeur et rappellent beaucoup celle du sous-genre Mycocepurus.

Queen
Moffett (1987) - Total length about 6 mm, with little size variation. Head width of three Singaporean gynes 1.05-1.06 mm; head length 1.08-1.10 mm; cephalic index 96-98. Head similar to that of worker, but roughly triangular in full face view; eyes oval, maximum diameter about 20% of head length; ocelli prominent; mandibles and antennae as in worker. Trunk massive, with full complement of flight sclerites, and only about 25% longer than high; very similar in shape to that of Atta gynes. Metanotum with a single blunt spine medad, as in male. Petiole and postpetiole as in worker. Gaster heavily sclerotized, massive, of a length slightly greater than that of ali trunk. Head and alitrunk areolate-rugose (with alveolate microsculpturing) as in workers but more strongly impressed.

Male
Male. Longueur, environ de 2mm, 5. Scape bien plus long que la tete. Abdomen aussi large que la tete. Entierement brunatre avec les pattes et les antennes plus claires. Les dents de l'occiput sont un peu plus longues que les autres. Du reste comme l'ouvriere.

(as given for the genus) Memes differences pour le nombre des articles des antennes. Mais toutes les epines sont transformees en dents plus ou moins mousses. Epistome, aretes frontales, carenes laterals comme chez l'ouvriere. Des sillons convergents au pronotum. Scutellum tronque derriere, presque bidente. La meme dent anterieure, mediane et unique que chez l'ouvriere. De fortes dents paires en arriere de l'epinotum. Les ailes chiffonnees paraissent semblables a celles des Atta. Premier noeud du pedicule tres faiblement impressionne au milieu.