Fig. 1. Five representative GC-MS chromatograms showing the emission from one single Pieris napi male, one P. napi male interacting with one male of Pararge aegeria, two P. napi males, and one P. napi male and one virgin P. napi female, and one P. napi male interacting with one mated P. napi female. Volatiles were collected by SPME for 1 h. The two main compounds were neral and geranial, with approximate proportions of 1:1. IS, the internal standard, n-pentadecane.