Abstract The hemolymph from the kissing bug, Rhodnius prolixus, contains two major proteins, i.e. storage protein (SP) and lipophorin (LP) in all stages of both sexes, and egg yolk main protein precursor vitellogenin (Vg) in the adult females. We studied changes in the profiles of SP, LP and Vg in the hemolymph and their synthetic activities during nymphal and adult development. Bugs were labeled in vivo with [ 35S]methionine, hemolymph was separated by native or SDS-PAGE, and visualized with Coomassie blue and fluorography. SP and LP are detected in the hemolymph of both sexes throughout life. Vg appears only in the hemolymph of females both immediately after adult emergence and after engorgement in starved adults. SP is observed both in the fat body and the ovary throughout the nymph and adult stages. Vg (or Vn) is detected in the adult fat body and ovary. SP synthesis is detected in every stage of development and reproduction. The synthetic activity of SP increases after engorgement and decreases during starvation in both nymphs and adults. In autogenous and blood-fed reproductive female adults SP synthesis is reduced except during a short time after emergence and after engorgement. The level of LP synthesis is lower than that of SP and Vg, but detected during the entire life span. In adult females, Vg synthesis is superior to SP synthesis both after emergence and after engorgement. Synthesis of both SP and Vg are detected in the fat body and the ovary. Both SP and LP synthesis are induced in decapitated adult females and males after JH treatment, whereas no protein synthesis is detected in acetone treated animals. Vg synthesis increases greatly after 4 days of JH treatment in adult females and is maintained at a high level for at least 1 week.