Ecdysone biosynthesis in the blowfly Calliphora stygia

3β,14α-Dihydroxy-5β-[3α-3H]cholest-7-en-6-one (1) is metabolised in Calliphora stygia at the time of puparium formation via hydroxylated derivatives to α-ecdysone (2) and β-ecdysone (3) and thus may be a precursor of ecdysones in this insect.