Behavioural bioassays with the pollinators. Comparative level of attractiveness of floral odour extracts of each taxa in the hybrid zone towards patrolling male bees. A. Colletes cunicularius, the pollinator of Ophrys arachnitiformis; B. Andrena nigroaenea, the pollinator of Ophrys lupercalis; C. Andrena vaga. One-Way ANOVA with LSD post-hoc test (a = 0.05). Different superscript letters on top of error bars indicate significant differences; the number of replicates is listed underneath the columns.