ASYNCHRONOUS RHYTHMS IN THE EMISSION OF VOLATILES FROM HESPERIS-MATRONALIS FLOWERS

Twelve monoterpenes and five aromatic compounds were identified from H esperis matronalis flowers in situ. The most abundant compounds were 1 ,8-cineole, E-beta-ocimene, linalool, and benzyl acetate. These four c ompounds were released asynchronously by the flowers during a photoper iod of 15 hr light and 9 hr darkness: 1,8-cineole was released mainly during the light period, E-beta-ocimene mainly near the switch from li ght to darkness, and benzyl acetate mainly during the dark period. Lin alool was not released rhythmically. Release rates of monoterpenes wer e higher at 20 degrees than at 15 degrees, while release rates of the aromatic compounds were not significantly different at these temperatu res. The role of flower volatiles in host plant finding by a specializ ed Hesperis feeding weevil, Ceutorhynchus inaffectatus, is discussed.