Thirty-three teneral Colorado potato beetle males were provided with non-transgenic foliage for 8 d, another 33 males were provided with non-transgenic foliage for 4 days, and then switched to transgenic foliage for another 4 d, and the remaining 33 males were provided with transgenic foliage for 8 days and then mated to females continuously fed on non-transgenic foliage only. Seventy-five percent of the males continuously fed transgenic foliage died during the first 8 d after eclosion. Only one of the females that mated to surviving males laid a single mass of fertile eggs, producing a total of 14 larvae. All the males from the other two treatments survived throughout the experiment. Ninety-four percent of the males fed non-transgenic foliage and 85% of the males fed both non-transgenic and transgenic foliage sired viable offspring. On average, one fertile female mated to a male fed non-transgenic foliage produced 353.3 eggs (SE=15.9) giving rise to 248.6 larvae (SE=15.9), and one fertile female mated to a male fed both on non-transgenic and transgenic foliage produced 322.9 eggs (SE=22.9) giving rise to 218.9 larvae (SE=18.1). Neither mean number of eggs, nor mean number of larvae was significantly different between the treatments. These results indicate that susceptible Colorado potato beetle males arriving in transgenic potato fields from refugia can mate with resident resistant females.