Synopsis

Bean beetles (Callosobruchus maculatus) are phytophagous insects that lay their eggs on the surface of several species of beans in the family Fabaceae. Larval development is completed within the bean.  Therefore, we would expect strong selection when the beetle switches to a new host. Students are provided with live cultures of beetles containing adults that have been raised on mung beans (Vigna radiata) for many generations; they also are given cultures that were originally grown on mung beans, but were recently switched to another bean species. In this exercise, students design and conduct an experiment to determine whether beetles have adapted to the new host. In the first class period, students design and set up the experiment. In subsequent sessions, they isolate beans with eggs and record data on life history traits including time to emergence and mass at emergence to evaluate the success of beetles on their historic and novel hosts.

Topic: Evolution

Level: Upper-level majors

Class time: one 2-3 hour class period, plus 1 hour class period 48 hours later, 15 minutes daily for 2 weeks about 4 weeks later