Ants and aphids are known for their mutualistic relationships in which aphids will provide ants with honeydew. The ants in turn, will protect the aphids from predators. However, not all ants will protect aphids all the time. One ant species, Lasius niger, will at some times tend aphids and protect them from predators. At other times, they will consume the aphids as food for themselves and the colony. To Protect? or Prey? How does an ant decide?Hiroshi Sakata carefully observed ant-aphid interactions to answer the question, “How does an Ant Decides to Prey on or to Attend Aphids?” Sakata found that Lasius niger will prey less often on a species of aphid they have tended and more often on a species they have not attended. This suggests that the ants can and do learn to identify aphid species.
Within an aphid species, individual aphids that have been tended by an ant or aphids that have provided honeydew to an ant are less likely to be eaten. This suggests that ants that are attending an aphid may mark the aphid with a colony specific substance.
Ants use odors for a variety of purposes including navigation and nest mate recognition. Marking individual aphids would be a useful signal for the ants that says, “Get honeydew here” and a useful signal for the aphid that says to the ants, “Don’t eat me”.
*Hiroshi Sakata. How an Ant Decides to Prey on or to Attend Aphids. Res. Popul. Ecol. 36(1), 1994, pp. 45-51.