Colorado potato beetle, Leptinotarsa decemlineata (Say), is an important pest of potatoes Solanum tuberosum L. worldwide. To control this insect, commercial growers in North America may increasingly rely on planting transgenic potatoes that express the Bacillus thuringiensis (Berliner) subsp. tenebrionis Cry3A toxin in their foliage (Whalon and Ferro 1998). Because persistence and distribution of the toxin in these plants are maximized (Perlak et al. 1993), there is strong selection pressure towards development of resistance to the Cry3A toxin in beetle populations (Ferro 1993). One strategy proposed to delay development of resistance is to provide spatial refugia of nontransgenic potatoes to support populations of susceptible individuals sufficient to curtail matings between resistant individuals (Whalon and Ferro 1998). Therefore, it is important that susceptible beetles moving into the transgenic crop from refugia can successfully mate with local resistant beetles. Wierenga et al. (1996) reported that adult beetles that fed continuously on transgenic potatoes since eclosion from pupae did not display any reproductive activity, but that successful reproduction was eventually observed if beetles fed on nontransgenic foliage later. Under field conditions, however, it is more likely that susceptible beetles emerging from pupae in refugia will feed on nontransgenic potatoes before, not after, moving onto transgenic plants. We have recently discovered that under such circumstances female beetles remain reproductive, but with significantly reduced fecundity relative to control females continuously fed on nontransgenic foliage (Alyokhin and Ferro 1999). No such data are currently available for male beetles.