ASSORTATIVE MATING IN 2 PHEROMONE STRAINS OF THE CABBAGE-LOOPER MOTH,TRICHOPLUSIA NI

The evolution of animal communication systems is an integral part of s peciation. In moths, species specificity of the communication channel is largely a result of unique sex pheromone blends produced by females and corresponding specificity of male behavioral response, Insights i nto the process of speciation may result from studies of pheromone str ains within a species in which reproductive isolation is not complete. Toward this end we investigated assortative mating based on female ph eromone phenotypes and male response specificity between mutant and no rmal colonies of the cabbage looper moth, Trichoplusia ni. There was n o evidence of assortative mating in small cages in which the density o f moths was high. In larger cages with lower densities of months, asso rtative mating was evident. In these larger cages, matings between nor mal males and normal females and mutant males and mutant females were more frequent than interstrain matings. Wind tunnel tests indicated th at normal males responded preferentially to pheromone released by norm al females, whereas, nutant males did not discriminate between normal and mutant pheromone blends. In large field cages, pheromone traps bai ted with normal females caught equal numbers of mutant and normal male s, while pheromone traps baited with mutant females caught primarily m utant males. The overall pattern of assortative mating could be explai ned primarily based on the normal males' preference for the pheromone blend released by normal females.