The name harvester ant implies vegetarianism but this is not strictly true. They will eat pretty much anything that contains a bit of nutrition. They do eat seeds in abundance however, mainly from grasses. Several of the grass species actually seed themselves and grow on the ant-hill waste heap so food is just on the doorstep for the ants. They will also eat the seeds from numerous other plants as well as the nectar and pollen from their flowers.
A wide range of carnivorous behaviors is reported for harvester ants. These will include the process whereby the queen will feed unhatched eggs to her first brood. These are called trophic eggs and this behaviour is unique to this species. I am not aware of any examples of cannibalism among harvester ants so your ant farm should be a peaceful community. It is termites, the soft bodies, types that make up about 70% of the ants’ meat consumption. Other larger insects, such as grasshoppers and crickets form the remainder, often the ants will remove the soft tissue from the inside of the insect?s exoskeleton if they cannot move the entire insect to the nest.
The most common foraging strategy is individual foraging. In individual foraging, singleton workers will leave the ant nest to forage for food alone. This is thought to be the most primitive of the hunting strategies but also one that is likely to result in the highest rate of losses. A simgle ant is far more vulnerable to predation from other species than a whole group of ants would be. This leads us on to group foraging behavior which is quite extraordinary. Many species, including the Florida, western and red harvester exhibit this behaviour and this is one of the reasons for their success. Sometimes, columns of ants over 100 feet long and two inches in width can be seen and woe betide any small animals that stand in their way. When a group attack takes place the insect (it?s usually an insect) is cut up and taken back to the nest. Often different ants will assume different roles when dealing with prey, from attacking, to dismembering and even digging underneath large prey to make it easier to move. Although the armies of harvester ants on the move are a fearsome sight to many animals, it should be remembered that not all foraging trips are successful. They only come back with food about 60% of the time. So the ants in your ant farm ought to be eternally grateful that you are providing them with food without their having to move from their doorstep.