AbstractNumerous studies have demonstrated regulation of specific lepidopteran proteins by pharmacological doses of insect juvenile hormone (JH). In this study, topical application of a 1 pg dose of JH I to fourth stadium larvae of theblack(bl) mutant strain of the tobacco hornworm,Manduca sexta, induced a 50% increase in the titer of hemolymph juvenile hormone binding protein (hJHBP). Radioimmunoassay confirmed that JH titers were lower inbllarvae than in wild‐type larvae at the time of JH treatment. Enzyme immunoassay analysis of hJHBP titers demonstrated that regulation by JH I was dose‐dependent at doses up to 10 pg and that the response was saturated above 100 pg. Western blotting and equilibrium dialysis confirmed these results and demonstrated that hJHBP frombllarvae had the same molecular mass and displayed the same affinity for JH I as hJHBP isolated from wild‐type larvae. Time course studies showed that regulation was complex: 1 2 h after JH I treatment, hJHBP titers were twofold lower in treated than in controlbllarvae, while 44 h after treatment they were twofold higher. JH I regulation of hJHBP titers inbllarvae was independent of changes in total hemolymph protein. © 1995 Wiley‐L