Studies on the diapause of Trogoderma granarium: Effects of juvenile hormone analogues on growth and metamorphosis

Trogoderma granarium larvae reared at 30°C on wheat flour containing appropriate concentrations of farnesyl methyl ether (FME) resembled normal diapause larvae in their growth characteristics and reactions to diapauseterminating conditions. When these larvae were transferred to 37°C either without food or with normal food, normal adults resulted. But when the diapause-like state was broken at 37°C in the presence of the original FME-containing food the insects either died before pupal-adult ecdysis or gave abnormal adults. At 35°C FME did not inhibit the larval-pupal ecdysis, but only a few adults emerged and these were abnormal.Farnesol did not inhibit metamorphosis at 30°C and caused less abnormality than did FME.Based on these results, the hypothesis that the density-dependent diapause of this insect is caused by the presence, in faecal pellets, and thereby in contaminated food, of juvenile hormone (JH) analogues is rejected, but the possibility that diapause results from a high physiological level of JH brought about by causes other than the presence of JH analogues in the environment is examined.