Newly-laid eggs of Locusta migrutoria contain as the major ecdysteroid conjugate donated by the female lo its offspring the 22-adenosinemonophosphoric ester of 2-deoxyecdysone (3): during embryonic development this conjugate is hydrolysed to free !-deoxyecdysone (1). which is subsequently metabolized IO 3-dehydro 2-deoxyecdysone (7) and 2-deoxy-3-epi-ecdysone(5): the latter substance is accumulated at late stages of development as a 3-phosphoric ester (6). 2?-Phospho-?-deoxyecdysone (4) also appears as embryonic development proceeds. either from partial hydrolysis of the maternal conjugate or from phosphorylation of free 2-deoxyecdysone(1).