Figure 2. Effect of diet on the mean durations of the four larval instars and of the pupa of the CPB. P-diet-I and LP-diet-I = P and F1 generations reared on Potato and Lettuce+Potato diets, respectively; P-diet-II and LP-diet-II = F7 and F8 generations reared on Potato and Lettuce+Potato diets, respectively; and L-diet-I = F8 generation beetles reared on the Lettuce diet (diet which contains 2.5% lettuce leaf powder and no potato leaf powder) during the F8 generation (P through F7generations had been fed the Lettuce+Potato diet). See Table 1 for description of the diets. For each experiment, each treatment group contained between 50 and 75 beetles (except for the Lettuce group which contained between 25 and 50 individual insects), and each experiment was performed at least three times. Since mortality reduced the total number of individuals, each value represents the mean of at least 50 separate determinations. A one-way ANOVA and the Tukey's HSD test were used to determine if there were significant differences among treatment groups. For any given stage, means ( S. E.) followed by the same letter were not significantly different.