Maize (Zea mays) has been transformed to express the Cry34Ab1 and Cry35Ab1 genes (Cry34/35) from Bacillus thuringiensis strain PS149B1. These two proteins act together as a binary insecticidal crystal protein that is active against larval corn rootworm (Coleoptera: Chrysomelidae) species. The transformed plants containing event DAS-59122-7 confer a high level of root protection from corn rootworm larval feeding. This high level of root and yield protection is the result of effective larval exposure to Cry34/35 insecticidal proteins in maize roots. Effective larval exposure is a quantity of Cry34/35 insecticidal proteins that, when encountered by a larva, prevents substantial feeding or injury to maize roots. The insect response to effective exposure may range from acute mortality to sub-lethal effects that result in reduced utilization of the maize host. The first objective of this study was to characterize the fate of larval western corn rootworm after exposure to DAS-59122-7 maize seedlings beginning at each of three instars. A second objective was to characterize the ability of western corn rootworm larvae to recover on conventional unprotected (non-transgenic) maize after exposure to DAS-59122-7 seedlings. The methodology accounts for the full range of potential insect responses through the use of an on-plant exposure scenario. Results suggest the effect of DAS-59122-7 on western corn rootworm larvae is best described as chronic and not acute. The mortality effect of DAS-59122-7 maize is largely a function of instar and the probability of any instar locating a suitable alternate host.