The efficacy of pitfall traps baited with pheromone and cereal oil in capturing Tribolium confusum Jacquelin du Val and T. castaneum (Herbst) (Coleoptera: Tenebrionidae) was low (trap catch) in mill and simulated warehouse settings. In a simulated warehouse experiment, strains of Tribolium Macleay recently taken from mills were caught 24% less often in traps than were laboratory strains, and T. confusum was caught 40% less often than T. castaneum. Both species were found together in all flour samples taken from a Canadian flour mill. A comparison of the species ratio in flour samples with that found in traps revealed that T. confusum was caught less often in traps than was T. castaneum. In flour, T. castaneum burrowed more than did T. confusum, and there were differences in burrowing behaviour between the four T. castaneum strains. Mills infested with T. confusum may have higher levels of infestation than was previously thought, indicating that further research into beetle behaviour in mills is needed.