RP-HPLC/RIA analysis of whole body extracts during the third larval instar in Drosophila. The ecdysteroid content, as measured by RIA using either the H22 (black) or SHO3 antisera (red) is shown for each HPLC fraction (1 ml) in selected samples as indicated (in hours after ecdysis to the third instar). (VPP), very polar products; (E), ecdysone; (20E), 20-hydroxyecdysone; (26E), 26-hydroxyecdysone; (20,26E), 20,26-dihydroxyecdysone; (3D20E), 3-dehydro-20-hydroxyecdysone; (20E'), 3-α-epi-20-hydroxyecdysone; (MakA), makisterone A; (20dMakA), 20-deoxymakisterone A (24-methylecdysone); 44, combined larval and white puparial (44WP) extracts; (WP + 4 hr), pre-pupae 4 hr after formation of white puparia.