Initial and delayed mortality of late-instar larvae, pupae, and adults of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) exposed at variable temperatures and time intervals

Late-instar larvae, pupae, and adults of Tribolium castaneum (Herbst), the red flour beetle, or Tribolium confusum (DuVal), the confused flour beetle, were exposed for variable durations at 36–54 1C. Beetles were placed in laboratory ovens set at a baseline of 27 1C, the temperature was increased by 0.1 1C per minute until the target temperature was achieved, and beetles were then held for specified exposure durations. There was no mortality after initial exposure or after a 1-week holding period of any life stage of T. castaneum or T. confusum exposed for 32 h to 36, 39, or 42 1C. At 45 1C, there was no initial mortality of either species exposed for different time intervals except for those exposed for 28 h. However, there was a significant increase in mortality after the 1-week holding period of those beetles exposed initially for at least 16 h to 45 1C. There was a sharp increase in mortality after the initial exposures of 4 h at 48 1C; mortality of T. confusum larvae was 90.075.7% but was only 10.0710.0% for larvae of T. castaneum, and no pupae of either species were dead. All life stages of both species were killed after the initial exposure of 12 h, and 1-week mortality of beetles exposed for 4 and 8 h was generally greater than initial mortality. At 51 and see front matter Published by Elsevier Ltd. jspr.2004.10.003 r reports the results of research only. No recommendations are given nor implied by the US Department . ding author. Tel.: +1 785 776 2783; fax: +1 785 537 5584. ress: [email protected] (F.H. Arthur).