[en] Malathion resistance in the red flour beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is actually a worldwide problem, and studies on resistance transmission are needed to improve insecticide resistance management. Females of Tribolium castaneum commonly mate with several males, and the last batch of male sperm preferentially fertilizes subsequent eggs. This phenomenon, a particular form of sexual selection, helps to increase resistance transmission in populations of stored product insects. We confirmed the last male sperm precedence and, in the absence of further matings, examined the evolution of mixed susceptible and malathion-resistant progeny during a 3-month period. The proportion of resistant phenotypes in female progeny was 99.6 and 3%, respectively, after the first mating with a resistant male and the second mating with a susceptible one. When females thus mated twice were isolated from males, the proportion of the resistant phenotype increased to 34.1% after 30 days. From 72 days onwards, this proportion ranged from 14.2 to 29.7%. (C) 1997, Published by Elsevier Science Ltd.