This species is sometimes erroneously called the 'Asian Bullet Ant'. This common name seemed to originate from an ant seller many years ago and was obviously given to help promote his sales of this particular species.
In Thailand and Asia generally, the ant called the ‘Bullet Ant’ (by the locals) with a sting much more venomous and painful is Tetraponera rufonigra. It would seem that some sellers looking for information on D. rugosum have just blindly copied past information on its common name, without taking time to do more detailed research.
This is a medium-sized primitive ant about 8 - 10 mm long. They are black, but in sunlight take on a glaucous appearance, which is caused by a fine covering of brown hairs. The actual exact identification of this species is difficult as there are 25 subspecies and varieties of D. rugosum recorded, many of which are only differentiated by microscopic details.
It is a hunter-gatherer species that is equally active both day and night. Single solitary workers roam tropical forests looking for food, which usually consists of dead insects and to a lesser extent any sweet secretions they can find. If a forager discovers food that is too heavy to carry back to its nest alone, it will return to the nest and lead a small group of workers which move in a tandem fashion across the forest floor to the food source. They are very inquisitive and will test any object they encounter for its food potential.
This species does not have a queen caste and a mated worker called a 'gamergate' acts as a functional queen. There is only one dominant egg layer in each colony, which looks just like the other workers, so is very difficult to differentiate.
This species does not have alate flights but propagates by colony division. In areas where the colony thrives and can find plenty of food, it will quickly increase in size to over a hundred individuals, and it will then split, with half the colony moving away to a new nesting site. The fertile gamergate will often move with the part that forms the new colony leaving behind 40 - 50 workers and some brood. As this brood matures and new workers emerge, they will fight amongst themselves until a dominant leader emerges. Once this ‘alpha’ worker has established her dominance, she will frequent the area just around the entrance of the nest and release a strong phenome (scent), which attracts males from other colonies who will mate with her. She then becomes the new egg-laying gamergate for the colony.
At intervals the colonies will produce males which are yellowish red with very long antennae - these leave the nest in the early morning and mate with receptive workers from other colonies.
They only raise a small amount of brood at any one time and the eggs, instead of being kept in a sticky mass like many other species are constantly held in the jaws of the workers. The larvae are very active and can be seen to wave their heads around when they are hungry and looking for food, and their pupae are enclosed in thick dark brown cocoons.
In the wild nests of very small ants are frequently found in close proximity to the Diacamma nests. These species benefit from the protection the larger Diacamma offer and feed on the leftovers of their food. This suggests that this species could be kept in a community tank with other smaller non-aggressive species.
They form small colonies usually from 50 to 150 individuals and nest in open deciduous forests at lowland altitudes. They usually nest in the ground constructing three to four small chambers about 10 – 15 cm below the surface. The nests only have a single entrance which is often surrounded by a small mound of excavated earth. Occasionally during the wet season, when there is a danger of ground nests becoming flooded, they will create nests in old wood and hollow bamboo. They will frequently change their nesting sites if conditions become unfavourable or if their nests are disturbed.
In the dry season when there is often no rain for several months workers have been recorded collecting hygroscopic objects such as small bird feathers and arranging them around the entrance to their nests. Then in the early morning natural dew forms on these objects, providing the ants with a source of moisture during a time when no regular source of water is available. This enables them to survive over the dry/hot season and to colonize areas other species which require moisture cannot.
It is an easy species to keep in captivity and because of the colony size does not need a very large habitat area. However, like many Diacamma they like to change their nesting location frequently, so it would help to have a set up with two artificial nests, so they can alternate between them, and this would also allow you to regularly clean the one not being used.
They also seem to be quite adaptable regards temperature and can be kept at normal room temperature, although this slows down the brood’s cycle, it also slows down the ant’s metabolism so they live a bit longer.
Warning: Be wary of buying low-priced colonies that only have a small number of workers (10 - 30) as this size colony does not exist naturally. Some sellers knowing that it is not possible for the hobbyist to identify the egg-laying ‘gamergate’ from the other workers, will split larger colonies into two or three separate parts just so they can make more money, and then obviously only the division with the gamergate will be viable.
In summary: Because of the colony size and adaptability to temperature, this is one of the easiest tropical species to keep. They are not fussy regards their food, will adapt to most artificial nests and do not require a very large foraging area.