The sex pheromone gland of female, T. atristriga contained at least six candidate pheromone compounds that elicited EAD responses from male antennae. None of these compounds was attractive when tested alone. Only a binary blend of Z11-16:Ac and Z11-16Ald at a ratio of 75:25 was attractive to males in one location (Lincoln), while this blend was not attractive when tested in another location (Little River) just 50 km away. Interestingly, the minor compounds (16:Ald, 16:Ac, 18:OH and Z3Z6Z9-23:Hy) did not enhance male attraction in Lincoln, while in Little River at least Z3Z6Z9-23:Hy was critical for male attraction and the addition of the remaining compounds (16:Ald, 16:Ac, and 18:OH) significantly enhanced male attraction. These results suggest that there are two populations of T. atristriga in Canterbury with different response profiles to female sex pheromone. In the Lincoln population, males responded to a binary blend of Z11-16:Ac and Z11-16Ald at a 75:25 ratio with no synergistic effect of the minor compounds. Meanwhile, in the Little River population, males showed a more conservative response to the female sex pheromone blend and they responded only to a complex pheromone blend including the same binary blend plus the other four minor compounds. Analysis of the pheromone gland with GC/MS and GC/EAD indicated similar pheromone gland contents and male EAD response profiles. Therefore, it is unlikely that these two populations are two distinctly different strains because the females of each population produce the same pheromone blend and therefore we anticipate there will be no reproduction barrier between these two taxa based on the sex pheromone.