Svoboda, J.A., Insect Physiology Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, 20705, Maryland, United States
Thompson, M.J., Insect Physiology Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, 20705, Maryland, United States
Robbins, W.E., Insect Physiology Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, 20705, Maryland, United States
Elden, T.C., Applied Plant Genetics Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, 20705, Maryland, United States

Radiolabeled sterols,14C-cholesterol,14C-cholestanol,3H-stigmasterol,3H-stigmastanol, and3H-sitosterol, were fed to larvae of the Mexican bean beetle, Epilachna varivestis Mulsant, by coating soybean leaves. Free sterol and sterol ester fractions from treated insects were isolated and analyzed, and in each case nearly 30% or more of total radiolabeled sterols retained by the insect were found in the sterol ester fraction after 8 days. Δ5 sterols were readily reduced to stanols, and C29-stanols thus produced were dealkylated to cholestanol. Significant amounts of labeled lathosterol were formed from Δ5-C29 sterols; little, if any, radiolabeled cholesterol was detected in insects fed either of the labeled Δ5-phytosterols, stigmasterol or sitosterol. Sterol metabolism of this insect thus differs considerably from that found for most phytophagous insects. © 1975 American Oil Chemists' Society.