Newly emerged, adult P. ammicana males, reared on a
nymphal diet of commercial dog food, were separated
from a stock colony and placed on Noland’s modified
diet V (7) containing 0.1 yo cholester01-4-C’~, specific
activity 179,000 cpm/mg. The radiochemical purity of
the cholesterol, examined by paper chromatography
(8), was found to be greater than 95%.