SEX-PHEROMONE COMPONENTS OF PITCH PINE LOOPER, LAMBDINA-PELLUCIDARIA

Two methylated hydrocarbons, 7-methylheptadecane (7) and 7,11-dimethyl heptadecane (7,11), are sex pheromone components of female pitch pine looper (PPL), Lambdina pellucidaria. Compounds extracted from the pher omone glands of female moths were identified by coupled gas chromatogr aphic-electroantennographic detection (GC-EAD) and coupled GC-mass spe ctrometry (GC-MS) in selected ion monitoring mode. In field-trapping e xperiments, 7 and 7,11 in combination, but not singly, attracted numer ous male moths. 5,11-Dimethylheptadecane (5,11) was detected by GC-EAD in female PPL pheromone gland extract, but did not significantly incr ease attraction of PPL males to 7 plus 7,11. Although 7 was > 10 times more abundant than 7,11 in pheromone gland extracts, traps baited wit h synthetic 7 plus 7,11 at a blend ratio of 1:1, rather than 1:0.1 or 1:0.01, captured the most PPL males. The chemical communication of PPL and spring hemlock looper (SHL), Lambdina athasaria, is strikingly si milar. Both species employ 7 plus 7,11 as sex pheromone. Restriction o f SHL to forests with eastern hemlock or balsam fir and PPL to forests with pitch or other hard pines contributes to their reproductive isol ation. PPL and SHL may also use different optical isomers of enantiome ric 7 and stereoisomeric 7,11 to maintain specificity of their chemica l communication.