Development of the silkworm without juvenile hormones (JHs).

<p>Maintenance of larval characters before the larval-pupal and pupal-adult molts is the classical status quo role of JH. This JH effect is carried out through its receptor Met and the transcription factor Kr-h1. The <i>mod</i> mutants studied by Daimon et al. <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002591#pgen.1002591-Daimon1" target="_blank">[4]</a> lack a P450 enzyme (epoxidase) and cannot make functional JH, yet they do not enter metamorphosis until after two larval molts, producing precocious pupae instead of the normal fourth larval instar. This unexpected result suggests that the early larval instars might be insensitive to the lack of JH. Illustration: Martina Hajduskova.