Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Costa Rica to Brazil (AM, PA, ES). Costa Rica: rare in Atlantic and Pacific slope rainforest.
Black; very smooth and shining, forming a highly polished, reflective surface over most of body.
This species is part of a small group of species (formerly placed in the genus Termitopone) known to be specialized predators of termites (Wheeler 1936, Hoelldobler and Traniello 1980). They carry out group raids on termite colonies.
Workers of laevigata are polymorphic in size, a trait unusual in the Ponerinae. Wheeler (1936) gave a thorough morphological description of workers and the male. He claimed the worker caste was dimorphic, and described both the major and minor workers. In my experience the workers appear continuously variable in size, not strictly dimorphic, but there has never been a quantitative analysis of polymorphism in this species.
Wheeler (1936) included the following behavioral observations:
The following observations made by three different entomologists on Barro Colorado Island throw much light on the behavior of laevigata. Dr. C. P. Haskins, who has generously given me specimens of this ant, informs me that at about 3:00 p.m. on August 15, 1930 he encountered it in a compact column about four feet long and three or four inches wide crossing one of the numerous trails that have been hewn through the primitive forest on the island. Acompanying the mass of workers, which were in all probability migrating to a new nesting site, were several males and winged females.
A few years later Mr. Phil Rau found nests of laevigata which he described (1933) as being in the ground under a log or heavy leaf and as sometimes extending up into the log.
Probably the termite raids of these ants do not begin till the rainy season sets in. At least I saw no traces of them during my latest visit to the island, towards the end of the dry season (April 3-12, 1935). Dr. Emerson was more fortunate later in the same year, when he succeeded in witnessing the raids on three occasions, as will be seen from the following excerpts from his notes.
On July 14 he came upon a column of about 500 workers "returning from a raid on termites and marching for the most part in single file. About one out of every three ants carried from one to five worker or soldier termites in its jaws. They were returning to their nest which they entered through a small hole in the leaf-debris of the forest floor." He was unable to locate the raided termite colony. "The column was about 20 feet long, with about 25 ants to the foot. The termites carried were soldiers and workers of Amitermes beaumonti Banks and workers of Heterotermes tenuis (Hagen), both characteristic species of the dead wood on the forest floor. The ants were carrying no other insects but termites."
September 9 Dr. Emerson encountered a column of more than a hundred laevigata workers with termites (Anoplotermes (Speculitermes) sp.) in their jaws while others were seen returning without any prey. He traced the column to a distance of 25 feet along the trail to a hole in the ground from which the termite-laden ants were emerging. They were evidently raiding an underground gallery, but subsequent digging failed to disclose the termites. Later he found a few paralyzed workers and soldiers of Heterotermes tenuis under a leaf near their trail but no termites of this species were seen in the ants' jaws.
A few days later (September 13) he encountered laevigata workers entering holes in a log and raiding a colony of H. tenuis. Sawdust was seen around the edges of the holes, which had probably been made by the ants, but they were not actually seen in the act of breaking into the termitary. Dr. Emerson writes me that this and the preceding observations were made towards noon.
While I am writing this paper Dr. Haskins informs me that he has just found (February 1936) a large laevigata colony nesting both in the soil and a small superjacent log on Baro Colorado Island. The workers of the colony were aggressive and made active use of their stings while he was collecting some of the males and winged females.
In Costa Rica, I have observed this species very few times, as follows:
Heredia Province, 22km N Volcan Barba, 10¡20'N, 84¡4'W, 500m. Column carrying termite prey.
Puntarenas Province, Corcovado National Park, San Pedrillo, 8¡37'N, 83¡44'W, 20m. I watched what I assume was a colony movement. A compact trail was steadily and rather sedately moving through the forest. The column was emerging from a cryptic nest entrance in the leaf litter. There was a cloud of small Diptera hovering around the entrance. At 1530hr the last of the column left the old nest. I went to the front end and followed them to where they suddenly entered a similar nest entrance. This entrance was in the center of the scattered remains of a termite nest. I made a few counts of ants per time, and measured the total time it took the column to enter the new nest, and I estimated 1400-1800 workers. The column was carrying much large brood. At one point, I removed a leaf across which the column was moving. The column backed up for a while. Meanwhile, the anterior portion disappeared into the woods. After a few minutes, the backed-up ball of ants at the head of the delayed portion of the column broke, and they continued on the same path as their predecessors, even though these were not within sight. This suggests the presence of a trail pheromone. The total distance moved was around 30m.
Corcovado National Park, Cerro Rincon, 8¡33'N, 83¡29'W, 700m. Worker collection.
Ponera laevigata F. Smith 1858:98. Syntype worker: Brazil, Amazonas: Ega (=Tefe).
Pachycondyla gagatina Emery 1890 is a junior synonym of laevigata, and has type locality in Costa Rica.
Emery, C. 1890. Voyage de M. E. Simon au Venezuela (Decembre 1887 - Avril 1888). Formicides. Annales de la Societe Entomologique de France (6) 10:55-76.
Hoelldobler, B., J. F. A. Traniello 1980. The pygidial gland and chemical recruitment communication in Pachycondyla laevigata. Journal of Chemical Ecology 6:883-894.
Smith, F. 1858. Catalogue of hymenopterous insects in the collection of the British Museum. Part VI. Formicidae. London: British Museum (Natural History), 216 p.
Wheeler, W. M. 1936. Ecological relations of ponerine and other ants to termites. Proc. Am. Acad. Arts Sci. 71:159-243.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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