Date of Award


Degree Type


Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)


Biological Sciences

First Advisor

Evan Preisser


The relationship between predator and prey has traditionally focused on the act of consumption. More recently, interest has shifted to the intimidation of prey through predator presence and the resulting alterations in prey morphology, behavior, or development. These prey responses, broadly called non-consumptive effects, are energetically costly to prey and can result in changes in prey populations. The study of non-consumptive effects can help further explain complicated trophic level relationships and food webs. The pea aphid, Acyrthosiphon pisum (Hemiptera: Aphididae), is a small, phloem-feeding insect that has developed an array of anti-predator responses when threatened. Dropping from a host plant, the costliest of the pea aphid’s behaviors, has been subject to a wealth of previous literature. This thesis work explored the relationship between dropping behavior, alarm cues (an indication of predator threat), aphid density, and plant health. Pea aphids were added to broad bean plants (Vicia faba) at a low (five aphids) and high (fifty aphids) density and also for a short (one day) and long (five day) feeding period. The treatments were then exposed to a simulated predator via a present or absent alarm cue. The number of aphids that dropped were counted for all treatments. The presence of an alarm cue resulted in significantly more dropping than with alarm cue absent. The density of aphids and length of feeding time did not affect dropping behavior despite a reduction of new plant growth in the high density/long feeding period treatment from control.