Susceptibility of last instar red flour beetles and confused flour beetles(Coleoptera : Tenebrionidae) to hydroprene

Last instar larvae of the red flour beetle, Tribolium castaneum (Herbst), a nd the confused flour beetle, Tribolium confusum Jacquelin du Val, were eit her exposed for 8-144 h on concrete treated, with 1.9 x 10(-3)mg(AI) /per c m(2) hydroprene, or continually exposed on concrete treated with 9.8 x 10(- 4) to 1.9 X 10(-3) mg[AI] /per cm(2) hydroprene. In both tests,larvae were exposed and held at 27 or 32 degreesC and 40, 57, or 75% RH. When larvae we re exposed with no food to hydroprene for different time intervals, then tr ansferred to untreated concrete containing flour, consistent effects were p roduced only at 144 h. At this exposure interval, tile percentage of beetle s arrested in the larval stage after 3-4 wk was generally greater at 75% RH compared with 40 and 57% RH, but there were no differences between species or temperature. The percentages of dead adult red flour beetles and live a dults with morphological deformities were also greatest at 75% RH and defec ts were more prevalent in red flour beetles than in confused flour beetles. When larvae were continually exposed to different concentrations of hydrop rene on concrete that contained. flour, the percentage of arrested larvae, dead adults, and live adults of both species generally increased with conce ntration. There were more deleterious effects at 75% RW compared with eithe r 40 or 57% RH, and effects were more pronounced in the red flour beetle co mpared with the confused flour beetle. In both experiments, temperature eff ects were variable and inconclusive. Results indicate that continual exposu re of last instar red flour beetle and confused flour beetle to hydroprene can limit population development, but exposure intervals of >6 d may be req uired for maximum effectiveness.