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Seven workers from the stomach of a toad (Bufo regularis) taken at Stanleyville; a series of workers of all sizes from Stanleyville and Lukolela to Basoko (Lang and Chapin); also workers from Katala (J. Bequaert).
Dorylus nigricans HNS is the famous driver or army ant, which has so greatly impressed all the African explorers. In my ant-book I have quoted some of the accounts of the earlier observers. To the field naturalist the various races of D. nigricans HNS and D. wilverthi HNS are so similar in appearance and habits that he designates them all as "driver" or "army" ants. It is not surprising therefore that Mr. Lang's notes refer indifferently to both species. The four fine photographs (Pls. II, III, and IV) belong undoubtedly to D. wilverthi HNS (vide infra) but the following note probably refers to both species: "Wherever they go, even though the file be very small, the army ants clear a road that can be easily seen. But when a large army is passing, they not only build a road but also bridges and frequently even fill in all the depressions between the dried grass with particles of sand or soil until a perfect road has been constructed. Across a pathway used by pedestrians, where they are often disturbed, they build walls and regular tunnels even in the hardest ground. Particle by particle is carried out by the steady stream of small workers and the soldiers, large and small, watch on both sides of the line, ever ready to attack anything that may approach. They assume a very peculiar attitude, with mandibles wide open and the head and thorax bent up and back till it forms a right angle with the abdomen. When they seize anything, the abdomen can be torn off without their loosening their grip. They are greatly feared by the natives and even the greatest laggard moves rapidly when passing 'the line.'" In connection with the fact cited by the early explorers, that the drivers are able to kill large animals when confinement prevents their escape, Santschi's quotation of the following observation of Cruchet concerning D. nigricans HNS in Benguela is of interest: "Twice during the course of the year we have been compelled to take the cows out of the kraal and drive them elsewhere, because they bellowed so piteously. On looking into the matter we found that the Anommas caused all this disturbance by crawling into the natural orifices of the animals, especially the anus and vulva. A brooding hen had her head half eaten away, but would not abandon her eggs. On three occasions one of my comrads had to quit his chamber during the night and take up his quarters in the work shop."
According to Forel,1 a very interesting account of the habits of Dorylus nigricans HNS in East Africa has been published by Vosseler,2 but I have not had access to this paper. Forel's paper, however, contains reproductions of three of Vosseler's photographs, one showing the Anomma overwhelming HNS a white rabbit and the others showing its army on the march and crossing a stream. Prof. Emery, some years ago, kindly sent me copies of these photographs, which seem to me worthy of being again reproduced for the benefit of my American readers (Pl. V, figs. 1 and 2; Pl. VI, fig. 1).
The singular dichthadiigyne, or female of D. nigricans HNS , was discovered by H. Schultze in Uganda. It measures 29 to 31 mm. and has been carefully figured and described by Forel in the work cited above (p. 177).