Of Ants and Aphids

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?

Ants Tending Aphids in My Garden

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.

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.

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2 Responses to Of Ants and Aphids

Qing Xu says:

February 12, 2013 at 12:44 am

This article interested me because I planted many kinds of flowers and vegetables in my garden and aphids are one of the main enemies for my plants. I always see numerous aphids on the shady face of leaves and stems of plants, and sometimes, also the ants. However, I never know the relationship between ants and aphids. It’s amazing to find that ants are friends and also predators of aphids. The key is whether the aphids provide ants with food (honeydew) or not. Perhaps I can find a solution to the aphids problems in my garden with the ants method.

Robert Ake says:

February 13, 2013 at 12:09 am

This article provides a great example for how symbiotic the relationship is between certain ant species and aphids. It makes perfect sense that an ant would want to protect and be able to recognize their source of food. Marking the aphids that the ant’s recognize as a food source and one that needs protection is a brilliant way to maintain a source of food. By marking the aphids with a substance, its almost as if the ants lay down a road map to locating the aphids that is easy to follow. This article goes well with the material that we were reading from your textbook during this time in class, I like how the blog is relevant to the material in the course.