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Thesis Abstract – Julian (1992)


An Examination of an Ant-Aphid Relationship: Do Aphids Benefit?

Author and college:

Glennis E. Julian, Pomona College


May 1, 1992


Bachelor of Arts in Biology


Paulette Bierzychudek, Pomona College


Ant tending of homoptera is a widespread temperate interaction which is often mutualistic. When mutualistic, the tending ants benefit by feeding on the carbohydrate-rich honeydew excreted as a byproduct by the aphids, and the aphids benefit by the protection offered by the ants from invertebrate predators. This mutualism, however, has been found to be conditional on environmental factors. Time of year, size of aphid colony, species specificity, types of predators all affect whether the ants truly provide a benefit to the aphids. To test in the field whether or not ants were providing benefits to aphids, I examined a natural population of ants, Iridomyrmex humilis, tending an unidentified aphid on leaves of willow trees. I excluded ants from certain branches and monitored the populations changes. In the fall, I found no significant different in population size between the excluded untended colonies and the tended colonies. I concluded that during this time of year, the aphids do not benefit from tending.

For more information:

Contact Gail Sundberg – gail.sundberg@pomona.edu

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