Macromischoides aculeatus, Wheeler, 1920

Wheeler, W. M., 1922, The ants collected by the American Museum Congo Expedition., Bulletin of the American Museum of Natural History 45, pp. 39-269 : 189-190

Macromischoides aculeatus (Mayr)

Plate XVII, Figure 1

Stanleyville, [[worker]]; Avakubi, [[worker]], [[queen]]; Bafuka, [[worker]]; Medje, [[worker]], [[queen]], [[male]]; Isangi, [[queen]]; Leopoldville, [[worker]] (Lang and Chapin); Bumba, [[male]] (J. Bequaert) Many workers and females and four males.

The following note by Mr. Lang accompanies the specimens from Medje: "These ants build their nests by filling out interstices between neighboring leaves with a rough-looking, light mass of decomposed vegetable matter. They prefer densely leaved trees and there are sometimes several hundred nests on the same plant. If one touches the tree, the ants at once rush out of their nests in great numbers and hurry along the branches to reach the intruder. They cling to the human skin and double themselves up while biting and stinging. The result is rather painful and very annoying. There is no swelling but the pain endures for several minutes. All of the ants climb towards the head. The nests are often empty and contain only a few workers, but sometimes they are filled with brood and winged individuals. These ants have a strong odor, especially when rubbed between the fingers." In the plate (Pl. XVII, fig. 1) two of the nests are shown, one in situ, the other with one of the two thick leaves between which it was built removed.

M. aculeatus is so common in the Congo that its nests have been seen by several previous observers. Santschi1 says of these structures: "Their nest consists of the leaf of a tree or shrub rolled up and lined with a felt-work of very fine vegetable débris and of a mycelium bearing fructifications. It would be interesting to study this fungus where it grows and to ascertain whether or not it is used habitually by the ants as food and is cultivated for this purpose." Commenting on the variety rubroflava, Forel2 remarks that it was "found in nests woven of silk, fixed to leaves, and, according to Mr. Kohl, similar to those of Oecophylla and Polyrhachis . From this fact I conclude that the nest of T. aculeatum is probably only superposed on a woven tissue, i.e., it is a combination of carton and tissue, as I have proved to be the case in many species of Polyrhachis ."

Examination of a nest of aculeatus preserved in alcohol by Mr. Lang and conversation with Dr. Bequaert, who is well acquainted with the habits of the ant in the Congo, have convinced me that both Santschi and Forel labor under a misapprehension in regard to the structure of the nest. It consists of particles of the most diverse vegetable substances, bits of bark, dead leaves, trichomes, etc., loosely felted together and invaded by fungus mycelium, but the latter bears nothing resembling fructifications or ambrosial bodies such as are found in the gardens of funguseating ants. Dr. Bequaert informs me that aculeatus often nests in forests that are inundated during the rainy season and, as fungus hyphae in such situations in the tropics grow readily on any dead vegetable matter, it is not surprising that we should find them invading the loose carton of the aculeatus nests. These hyphae were interpreted as silk by Forel and suggested to Santschi the possibility of the ant being mycetophagous.