Graduate Program
Biological Sciences
Degree Name
Master of Science (MS)
Semester of Degree Completion
2009
Thesis Director
Paul Switzer
Thesis Committee Member
Ann Fritz
Thesis Committee Member
Eric Bollinger
Abstract
Insects in have several methods of advertising for mates; one important and common method is via the use of chemical pheromones. Insects release pheromones into the environment to communicate information about their sex, mating status and receptivity to others. For example, Japanese beetles (Popillia japonica) produce a very volatile sex pheromone conspecifics can readily detect. This pheromone is released by virgin females only, and triggers scramble competition among the males that detect and follow the signal for access to these females. Because Japanese beetles are an invasive species and an important pest of ornamental and agricultural plants, there is strong incentive to develop an effective trap to manage their populations and to reduce the damage they cause. The beetles' sex pheromone has been incorporated along with floral compounds into lures for these traps because of its strong attractive ability; however traps are still not completely effective. Some individuals fly to the trap's location but do not enter the trap itself, and still others fail to respond to the trap lures at all. Another limitation of beetle attraction via pheromone is that because the pheromone origin is female-specific, for the most part only males are pulled into traps by this additional lure. Occasionally, females have been observed to respond to sex pheromone, however, and investigations of P. japonica's antenna! structures have shown the presence of pheromone-detecting pores on females' antennal lamellae. This evidence of female response to pheromone and the observed differences in individual males' responses are interesting for their behavioral and economic implications, and this thesis consists of two experiments that attempt to investigate factors influencing individual responses to pheromone for both sexes and the effect, if any, the social situations of male beetles might have on their pheromone response patterns.
In the first experiment, trials were performed on individuals of both sexes to investigate the behaviors displayed during pheromone exposure and determine the effect ofrecent mating experience. Beetles were kept either with or without mates for ~24 hours before testing, and their behaviors were recorded as they were exposed to odorless (control) or pheromone-laden air inside an acrylic testing chamber. We found that female beetles do indeed appear to respond to the presence of pheromone; they fly more often in its presence and rub their abdomens more frequently. Males also displayed clear pheromone response behavior, especially through rubbing behaviors. Recent mating experience appeared to have an effect on an individuals' latency to start flying during a trial in conjunction with the presence or absence of pheromone; unmated beetles flew more quickly during the pheromone· exposure trials, and had greater latency to flight during control trials.
Beetles were also tested in group trails to investigate pheromone response behaviors in differing social scenarios; several trials were run on groups of 5 male beetles and mixed-sex groups of 3 males and 2 females. Each group was exposed to either a control of normal outdoor air or a plume of pheromone. While patterns did not emerge as clearly in these experiments, a significant interaction between the number of pairs formed during a trial and the ambient light level was observed that suggests that pheromone presence could have an effect on the level of an individuals' arousal level and the instigation of mating interactions.
Recommended Citation
Schoenick, Carissa A., "Behavioral response of Japanese beetles (Popillia japonica) to sex pheromone: Exploring factors of social situation and recent mating experience" (2009). Masters Theses. 56.
https://thekeep.eiu.edu/theses/56
