Abnormal melanization of tracheae in farnesoid (-) larvae. Most of the individually reared larvae expressing an RNAi that blocks expression of HMGCR in the corpora allatal cells were to observed exhibit tracheal melanization. The melanization started at the posterior end of the 2 main dorsal tracheal trunks, and rapidly spread anteriorly at or shortly after the 2nd instar to 3rd instar apolysis (A, B). In some cases, there seemed to be a positional periodicity to foci of the most darkened areas (C). Rarely, larvae that exhibited a lesser amount of melanization survived to pupate, and exhibit melanized streaks in the abdomen (D, E), and even more rarely, those pupae would survive to emerge as adults that still exhibited the tracheal melanization (F).