Pheromone components for many lepidopteran species are produced by the use of unique chain-shortening and Δ9, Δ10, and Δ11 desaturase systems. Correlations in the Tortricidae indicate that the pheromone components derived from Δ9 and Δ01 desaturases are found in the more primitive species (those possessing morphological plesiomorphies). The precise blend ofZ andE acetates in a number of species is regulated in the final reduction sequence from acyl intermediates. Preliminary research has been conducted on the characterization of the various desaturase enzymes used and on the important blend regulating sequence. Initial purification work on the Δ11 desaturase enzyme found in the cabbage looper moth is reported.