The regulatory effects of ants (Formicidae) on predation, growth, and honeydew production in colonies of aphids (Aphididae).

Abstract

Many studies have been done on the relationship between Homopteran species such as aphids (Homoptera: Aphididae) and their attending ants (Hymenoptera: Formicidae). The results of these studies, most of which have suggested that this relationship is mutualistic, have shown conflicting results regarding the benefits received by aphids in this relationship. The purpose of this experiment is to specifically look at how aphids are benefitted in this species interaction. Colonies of aphids on Populus balsamifera L. were studies at UMBS, Pellston, northern lower Michigan. Samples were set up with and without protection from predators and with and without tending ants to see how the presence of ants and predators affects the growth of aphid colonies. We measured growth by comparing the number of aphids in each colony over time. To study predation, we added lacewing larvae (Chrysopa spp.) to colonies of each treatment to see how they would react in the different environments of each. We found that the number of aphids did not significantly change over time, that ants protect aphids against predators, and that in the absence of tending ants, excess honeydew built up on leaves surrounding the colonies and that some colonies dispersed. It appears that the ants regulate aphid population size by keeping it from getting too large or too small.