Population dynamics of red flour beetle (Tribolium castaneum (Herbst)) under different temperatures and patch sizes

Abstract

Population dynamics of red flour beetles, Tribolium castaneum (Herbst), was determined using three different sizes of grain patch (bulk) at different temperature profiles. Grain patches were 0.03 kg, 2 kg, and 14 kg of wheat with 14.5% moisture content (wb). The temperature profiles tested were constant temperatures of 21, 25, 30, 35 °C, and incrementally decreased or increased temperatures (T-decrease (Td) and T-increase (Ti)). Every 28 d up to 168 d, the live and dead adults were separated from the wheat and their numbers counted. At Td, adults were separated and counted every 28 d during the first 140 d, then one last time 70 d later. After separating and counting, these adults were discarded and the wheat, which contained immature stages, was incubated at 30 °C. Four weeks later the emerged adults (referred to as “offspring”) were counted. The number of both adults and offspring showed great variation among temperatures at the same storage time and the same patch size. The peak number and density of insects also showed variation among different temperatures and patch sizes. Peak live adult density was the highest in the small patches. The peak live adult densities were 300 ± 50 at 21 °C, 673 ± 118 at 25 °C, 689 ± 48 at 30 °C, 1100 ± 150 at 35 °C, 1150 ± 150 at Td, and 1133 ± 94 adults/kg at Ti. The offspring density at 35 °C was higher than that at other temperatures in the small patches. Even though many factors and their interaction influenced population dynamics of T. castaneum, the number of insects was mainly influenced by temperature at the same patch size, while large patch size could provide more room for insects to multiply.