ELECTROPHYSIOLOGICAL AND MORPHOLOGICAL-CHARACTERISTICS OF PHEROMONE RECEPTORS IN MALE PINE SAWFLIES, DIPRION PINI (HYMENOPTERA, DIPRIONIDAE), AND BEHAVIORAL-RESPONSE TO SOME COMPOUNDS

The morphology and physiology of pheromone receptors on the antennae o f male pine sawflies, Diprion pini L., were investigated. Using scanni ng electron microscopy, five sensillar types were recognized. The type shown to be pheromone sensitive has a long (50-70 mu m) cuticular hai r, is single-walled, and is innervated by 8 or 9 sensory cells as reve aled by transmission electronmicroscopy. Electroantennography (EAG) sh owed similar activity of the acetate and propionate of (2S,3R,7R)-3,7- dimethyl-2-tridecanol, precursor of the main constituent of the female -produced sex pheromone. No other isomer induced any significant respo nse. Single-sensillum recordings confirmed the results of the EAG, and also showed that several neurons were excited by the active compound. EAG recordings and combined gas chromatographic-electroantennographic detection indicated that esters of three 3,7-dimethyl-2-pentadecanol (diprionol) isomers were active, but field tests could not demonstrate any behavioural effect. Diprionol esters are used as sex pheromones b y all other pine sawflies investigated so far, and D. pini is thus the first diprionid species shown to use a different sex pheromone.