The effect of ant (Formicidae) presence on growth, predation, and sanitation of aphid (Aphididae) colonies.

Abstract

The association between ants (Formicidae) and aphids (Homoptera: Aphididae) is well documented. The aphids provide honeydew as a food source for ants. The ants ensure this food source by protecting aphids from predation and by regulating the density of the aphid population. Regulation is necessary to reduce intraspecific competition and minimize damage to the host plant. The effect of ant presence on growth, predation, and sanitation of aphid colonies was measured. Ant presence stabilized the number of aphids per colony such that the percent growth of colony size was only -3.7%. In the absence of ants, the number of aphids per colony rose 233.3% without predators present, and decreased 63.2% with predators present. A predator, lacewing larva (Chrysopidae) was more likely to stay on leaves without ants (86% of the time) than on leaves with ants (14% of the time). Sanitation was reduced in colonies without ants present. These colonies contained sticky leaves because of the lack of removal of the excess honeydew. The ratio of dead to living aphids was higher in colonies without ants (0.68:1.00) than on colonies with ants (0.17:1.00). Ants presence regulates the number of aphids per colony to stable levels, inhibits predation, and maintains sanitary aphid colonies.