Repeatability of pheromone emissions from individual female ermine mothsYponomeuta padellus andYponomeuta rorellus

The repeatability of the composition of pheromone emitted by individual female moths (Yponomeuta) was determined by gas Chromatographic analysis. An improved technique for repeated collections of airborne volatiles from the same moth was developed. The procedure did not harm the females and allowed precise quantification of 0.05 ng of pheromone components in 30-min collections. Individual females ofY. padellus (N=10) andY. rorellus (N=5) were sampled six and eight days after emergence.Y. padellus released, on average, 4.8 ng/30 min of tetradecyl acetate, (E)-11-tetradecenyl acetate, (Z)-11-tetradecenyl acetate, hexadecyl acetate, (Z)-9-hexadecenyl acetate, and (Z)-11-hexadecenyl acetate in the average ratio 445∶38∶100∶494∶35∶421. The amount of (E)-11-tetradecenyl acetate relative to (Z)-11-tetradecenyl acetate was less variable [coefficient of variation (CV)=15%] than the relative amounts of the other components (CV=46-61%). The repeatability of the relative amounts of compounds released by individual females was high for all components (r=0.82-0.90). The average emission of tetradecyl acetate, tetradecanol, hexadecyl acetate, and hexadecanol byY. rorellus was 8.3 ng/30 min (ratio 100∶8∶10∶2). The repeatability was low for tetradecanol (r=0.51) but higher for hexadecyl acetate (r=0.87) and hexadecanol (r=0.89). The low interindividual variance for the (E)-11-/(Z)-11-tetradecenyl acetate ratio inY. padellus might be due to its importance for reproductive isolation, i.e., it is under strong selection pressure.