Fun with Science Club®


			Ants and aphids: friends or are they just using each other? Carrie Straight 05.14.01 Some ants and aphids have a unique relationship. The ants, Lasius niger and the aphids, Aphis fabae, are common to gardens in Denmark. The aphids produce what scientists call honeydew. The honeydew is a sugar-like solution excreted by the aphids. The ants eat the aphid honeydew for energy. The ants eat the honeydew directly off the aphids, keeping the aphids clean. The ants also remove dead aphids, protect the aphids from predators, and take aphids to new feeding sites. This relationship between the ants and the aphids seems good, except for one problem. Sometimes the ants eat the aphids. Some scientists wanted to know if the interactions between these ants and aphids change depending on the amount of other food available to the ants. To make systematic observations of the relationship between the aphids and the ants, researchers collected ants and took them to the laboratory. They placed the ants in Plexiglass boxes connected by glass tubes. They grew bean plants for the aphids to eat. They used four different combinations of food for the ants to eat, with and without prey (fruit flies (Drosophila melanogaster), house flies (Musca domestica) and mealworms (Tenebro molitor)) and with and without honey. The researchers found out that when they supplied honey, the ants did not collect as much honeydew, and they would prey on aphids more often. This showed that when ants did not need aphids for their honeydew production (because honey was supplied), live aphids were not so valuable to the ants and the ants ate them!


			Offenberg, Joachim. 2001. Balancing between mutualism and exploitation: the symbiotic interaction between Lasius ants and aphids. Behavioral Ecology and Sociobiology 49(4): 304-310.