“…This has been especially true for the critical third (final) larval instar when the insect must be reprogrammed so that it can undergo metamorphosis to the pupa and then the adult in response to a large surge in 20E, a phenomenon studied mainly in the Lepidoptera (Bollenbacher et al, 1975;Riddiford, 1976Riddiford, , 1995. The requisite involvement of ecdysteroid signaling in these complex processes is central to present theories of arthropod development (Ashburner et al, 1974;Yao et al, 1993;Buszczak and Segraves, 1998;Bialeccki et al, 2002;Lafont et al, 2005;Henrich, 2005). However, the RIA, particularly when applied directly to whole body extracts, yields only a rough estimate of the molting hormone titer, as each ecdysteroid component present gives a variable response (cross-reactivity) in the assay depending on affinity characteristics of the antibody used.…”