EPOW - Ecology Picture of the Week

 

Updates on Species Identification

EPOW reader Marcus Stüben, Ph.D. biology student at Theodor-Boveri-Institut für Biowissenschaften der Universität Würzburg (Biozentrum) in Würzburg, Germany, suggests that the species shown on this page might not be "Megaponera foetens" (which is a synonym of the valid name Pachycondyla analis, Ponerinae, Ponerini), but rather army ants, Dorylus species (Dorylinae), on a swarm raid.  Stüben wrote that Pachycondyla analis is a blackish species and has normally less numerous raiding parties.   However, another EPOW reader, Simon Williams of the BBC Natural HIstory Unit in Bristol U.K., has written that the species shown likely is Megaponera foetens.   Further, Dr. James C. Trager, Restoration Biologist and Ant Taxonomist with Shaw Nature Reserve, Gray Summit, MO, wrote that the species shown is "one of the African driver ants, probably Dorylus wilverthi.  He wrote, "Note the polymorphic workers, with large-headed majors guarding the flanks of the column" and that "Pachycondyla spp. by contrast have monomorphic workers, for example, this South American termite raiding species.        Dr. Trager also wrote:      From http://antbase.org/ants/africa/pachycondyla_1.htm comes the following information on Megaponera foetens, a.k.a. Pachydondyla analis:      "In Nigeria, studied at Mokwa, in the southern Guinea savannah, ... Longhurst & Howse .... described its predation on termites, and the biology of males. Almost half of the 73 nests which they examined were in deserted nests of the termite Macrotermes bellicosus (Smith), most of the rest were in the ground under bushes. Activity was either early morning (0700-0930 h) or late afternoon (1630-1830h). Major 'scout ants' locate foraging termites, by detecting chemicals in the soil sheeting built by the termites. The scouts then recruit other workers, scent trails being used once the route is established. Only the minor workers enter the ... [termite nest] and bring out captured termites, stacking the prey around the entry points. At the end of the raid the termites are carried back to the P. analis nests, mainly by the majors."      This site includes dimensions and pictures of the dull-headed majors and shiny-headed minors and a discussion of the taxonomic confusion caused by these different-looking castes. Still, most if not all other Pachycondyla species have monomorphic workers, and the picture is indeed of Dorylus. The raiding columns of P. apicalis have all workers going either to or fro, and lack the flanking ranks of much larger, outward-facing soldiers typical of Dorylus.      Later, Dr. James C. Trager (Ant Taxonomist, Shaw Nature Reserve, Gray Summit MO) wrote that the photos on this page are not of Pachycondyla analis (formerly called Megaponera foetens), but rather one of the African driver ants, probably Dorylus wilverthi.  He pointed out the polymorphic workers with large-headed majors guarding the flanks of the column.  These occur with Dorylus but not Pachycondyla spp. which by contrast have monomorphic workers, such as this South American termite raiding species (http://www.myrmecos.net/ants/PacMar1.html).      Dr. Trager also said that he cannot confirm if the term matabele is used for both Pachycondyla analis (which he says it is for sure) and for swarm-raiding driver ants, and suggests that perhaps the term matabele ant not be used at all because the photos posted on this page are not Pachycondyla.  Dr. Trager also wrote:      Dorylus spp. are mass-foraging, swarm-raiding army ants which have highly varied prey, and only opportunistically feed on termites or take up residence in their abandoned nests. They search for AND attack prey en mass, as is typical of all true army ants. I am not familiar with the chemistry of their trail and recruitment pheromones, and indeed, I don't think Dorylus trail pheromones have been chemically characterized.      P. analis, on the other hand, searches for prey singly, by means of individual scouts that go out looking for potential termite prey. Their raids are columnar rather than broad-fronted swarms, and are a separate event from the scouting expeditions, resulting from recruitment by successful scouts. A major component of their trail pheromone is N,N-dimethyluracil, and this compound appears to be unique to P. analis in this role. Finally, and in stark contrast to Dorylus, P. analis is a specialist predator on termites, never hunting other fare.      It is because of the deeply rooted phylogenetic, ecological and ethological differences between these two ants that I have been trying to make the distinction to the viewers of your page. I would make the radical suggestion that since the actual image is of a Dorylus species, that it would be best to confine the commentary to them, and not confuse the issue by bringing in the biology of another unrelated species. Apparently, the name "Matabele ant" is used by some authors for both Dorylus and Megaponera species, although Dorylus is actually a real army ant.   My sincere appreciation to all the EPOW readers and ant experts who contributed their knowledge and perspectives.

Next week's picture:  Vaux's Swifts

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