Specificity of sex pheromones, the role of host plant odour in the olfactory attraction of males, and mate recognition in the aphid Cryptomyzus

Choice tests in an olfactometer showed that males of the aphid Cryptomyzus galeopsidis spent more time in the odour of conspecific females than of a sibling species or a more distantly related Cryptomyzus species, which all co-occur on red currant. Analysis of the pheromone-emissions of females showed the presence of a nepetalactol and a nepetalactone, two known aphid sex pheromone components. However, no interspecific difference in the ratio of the components (c. 30:1) was found, and this ratio did not change as the females aged. Males were only slightly attracted by a synthetic 30:1 mixture of these two components, and in a choice test 'preferred' the odour of conspecific females. The sex pheromone of Cryptomyzus spp. must thus consist of more than two components, the first time this has been reported for aphids. Host plant odour did not attract males or enhance the activity of the pheromone.