3,13,DIMETHYLHEPTADECANE - MAJOR SEX-PHEROMONE COMPONENT OF THE WESTERN FALSE HEMLOCK LOOPER, NEPYTIA-FREEMANI MUNROE (LEPIDOPTERA, GEOMETRIDAE)

3,13-Dimethylheptadecane (3,13-dime-17Hy) is the major sex pheromone c omponent of the western false hemlock looper (WFHL), Nepytia freemani Munroe. It was identified in extracts of female pheromone glands by co upled gas chromatographic-electroantennographic detection (GC-EAD) and coupled GC-mass spectroscopy (GC-MS). Traps baited with 100 mug of 3, 13-dime-17Hy attracted large numbers of male WFHL. Of five additional candidate pheromone dimethylated hydrocarbons, only 3,13-dimethylhexad ecane attracted male WFHL. However, neither 3,13-dime-16Hy nor the oth er four compounds enhanced attraction to 3,13-dime-17Hy when tested in binary or ternary combination at respective ratios of 100:10, 100:1, or 100:1:1. Identification of the complete WFHL sex pheromone requires structural elucidation of all 12 EAD-active components in gland extra cts, determination of their chirality, and field testing of antennally active isomers in appropriate combinations and ratios. Stereoisomeric 3,13-dime-17Hy as trap bait may already be used to monitor WFHL popul ations.