At the tracheal dorsal trunk stage 17 embryos, expression of Blimp-1UAS.cOa in the posterior metameres (under the control of Scer\GAL4Abd-B-LDN) or in flip-out clones (under the control of Scer\GAL4btl.B123) leads to lower chitin levels, thinner tanedial folds and less anteroposterior elongated apical sided tracheal cells when compared to controls.