Dynamics Of Aggregation Formation In Japanese Beetles, Popillia Japonica

Abstract

For most insect aggregations to form, they need to be started by an initial individual (the pioneer) andjoined by later individuals (the joiners). Pioneers and joiners may differ with regard to characteristics such as sex and body size. We carried out three field experiments to examine the characteristics of Japanese beetles, Popillia japonica, pioneering and joining aggregations on host plants. Individual beetles were captured as they arrived on uninhabited grape plants, as well as plants designed to simulate aggregations with model beetles and feeding damage. For all experiments and treatments, the beetles arriving were significantly female-biased, with pioneer females having higher egg loads than females in aggregations. Females pioneering later in the day had higher egg loads than those arriving earlier. Male beetles found on uninhabited plants were smaller and arrived earlier in the day than males in the aggregation area of the experiment. These results suggest that female Japanese beetles are typically the initiators of aggregations (i.e. the pioneers) and males are joining later in the process, and that females with fewer eggs and males with larger body sizes are more likely to join aggregations. We use these patterns to hypothesize on the different uses of aggregations by male and female Japanese beetles.

Date of Award	2009
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Paul V Switzer (Supervisor)