Protein and carbohydrate are the two most important macronutrients that have profound impacts on fitness and demography in most insects. The purpose of this study is to investigate the effects of dietary protein:carbohydrate (P:C) balance and mating status on feeding behavior, longevity and fecundity in male and female mealworm beetles, Tenebrio molitor (Coleoptera: Tenebrionidae). In the first experiment, we measured the amount of protein and carbohydrate consumed by mated and unmated beetles of both sexes. Newly emerged beetles were allowed to mate for 24 h before they were simultaneously provided with two nutritional imbalanced but complementary synthetic diets (P:C =1:5 vs. 5:1) for 24 successive days. Mated females not only consumed significantly more nutrients but also exhibited a greater preference for protein than did mated males and unmated controls. In the second experiment, we determined longevity and fecundity from a total of 120 male and female beetles that were confined to feed on one of three no-choice foods differing in P:C balance (P:C=1:5,1:1 or5:1) throughout their entire lives. Fecundity was recorded as the total number of eggs laid by individual females until death. Both male and female beetles lived significantly longer and laid more eggs over the lifetime on a balanced diet (1:1) than on the two imbalance diets (1:5 and 5:1), suggesting that the Darwinian fitness was maximized when the diet was equally balanced in protein and carbohydrate. Mated male and female beetles had a shorter longevity compared to their unmated counterparts, indicating that there was a significant survival cost to mating in this insect.

• Myung Suk Rho(Department of Agricultural Biotechnology, Seoul National University, Seoul)
• Kwang Pum Lee(Department of Agricultural Biotechnology, Seoul National University, Seoul)