Figure 3.

Hormones effect juvenile and adult developmental programmes through mutual interactions of transcription factors. Bottom: phenotypes in Pyrrhocoris supporting the pathway scheme. An extranumerary larval instar (L6) can be induced either with the JH mimic methoprene or with E93 RNAi (iE93) early (on the first day) during the final larval instar (L5). E93 knockdown was achieved by injecting 3 µg per animal of double-stranded RNA encompassing the coding region of E93. Note that the wing pads of the aberrant L6 animals are larger relative to control L5 but similarly dark and unarticulated, external genitals undeveloped, and the notum retains the larval pattern. Conversely, precocious development of adult characters at the fifth instar was induced by knocking down Kr-h1 (iKr-h1) early during the L4 instar [21]. For details of RNAi treatments see Smykal et al. [22]. E93 and Kr-h1 are mutual repressors [23–25].