Defects in apical extracellular matrix. Embryos show defects in the formation of the innermost layer of the apical extracellular matrix and its attachment to the epidermis. Most larvae die during second-instar or second/third-instar interface, but some survive until early third-instar. Surviving larvae display cuticle defect and irregular tracheal morphology. Ultrastructural analysis of larval epidermis reveal disruption of the deposition zone of the endocuticle, leading to separation of the epidermis from the chitin layers.