ABSTRACT
Nutritionally, the phylum Arthropoda is most clearly distinguished from the vertebrates by an inability to biosynthesize sterols, despite analogous physiological needs for sterols in lipid biostructures and as steroid hormone precursors. Insects have been shown to be unable to condense farnesyl pyrophosphate to squalene and to lack squalene epoxide cyclase, the enzyme needed to catalyze the cyclization of squalene to lanosterol.19
