Regulation of hemimetaboly and holometaboly.

Pyrrhocoris (left) and Tribolium (right) cartoons signify the main innovations – postponement of wing development and the resting pupal stage in holometabolans. The absence of JH-dependent Kr-h1 expression in pupae and final instar hemimetabolous larvae (gray shaded areas) is prerequisite to adult development in both types of metamorphosis, supporting the view that these final juvenile stages of both insects types may be homologous [1], [35]. The orange shaded area marks a period of low Kr-h1 activity in the absence of JH, which is necessary to permit partial metamorphosis during the pupal molt, specified by the newly acquired function of BR-C in holometabolans. Gene expression profiles for Pyrrhocoris and Tribolium are from Figure 1B and from [17], respectively. JH and ecdysteroid titers are from Blattella germanica [34] (left) and Manduca sexta [5] (right).