The population dynamics of Tribolium castaneum (Herbst), red flour beetle, was studied at 30℃ using long vertical columns (LVCs) (150 mm diameter and 1020 mm long) and shallow containers (SCs) (460 mm long, 660 mm wide, and 150 mm high), containing 14 kg of whole wheat or a diet made of whole wheat and cracked wheat in 19:1 ratio by mass. The moisture content of the wheat or mixed diet was 14.5% (wb). Every 4 weeks and up to 24 weeks the live and dead adults were counted in the SCs or in each section of the LVCs. Each LVC was separated into ten equal sections before removing grain from the LVC. After counting, the grains were incubated at 30℃ and 70% RH for 4 wk, and emerged adults after re-incubation were counted as offspring. The adults and offspring were mainly concentrated in the top section of the LVCs, which could be due to higher mortality in the lower sections and the preference of T. castaneum for the surface of grain bulk. The diet influenced the population, and the insects developed better in the cracked wheat-based diet. The greater surface area of the container increased the multiplication and/ or survival of T. castaneum. Insects inside SCs with larger surface area and with cracked wheat-based diet, had a quicker population increase rate and larger carrying capacity than LVCs.