The effects of competition between larvae of stored-product moths

The competition between Idaea inquinata, Corcyra cephalonica, and Plodia interpunctella on an artificial diet was investigated. The experiments were carried out with eggs laid within 24 hours. In the first experiment, 20 eggs of one species were placed in a ventilated Petri dish with 10 g of diet and 20 eggs of one of the other species; in the second experiment, 20 eggs of one species and, after 7 days, 20 eggs of one of the other species were added. Experiments were carried out at 27±1 °C, 70±5% R.H. Each experiment was replicated 5 times and the number of days to complete the development and the number of emerged adults were recorded. The number of P. interpunctella adults was not affected by the presence of C. cephalonica or I. inquinata. A delay in the development was only observed when P. interpunctella eggs were added to the medium already colonized by the other species. I. inquinata was the less competitive, as the number of adults decreased and the days to complete the cycle increased. The development of I. inquinata was prevented if P. interpunctella eggs were started at the same time. Larvae of this last species cannibalized eggs of the other two species. I. inquinata was the least competitive due to the longer cycle, the lower mobility and the aggressiveness of the larvae of the other two species that cannibalized its eggs.