Pheromone-based assortative mating in a bark beetle

Assortative mating based on a courtship signal was investigated by examining the relation- ship between the male-produced pheromone and female preference in the bark beetle, Ips pint. Female preference in response to the male-produced pheromone was measured in the field using traps bailed with a range of 11 synthetic blends of the two pheromone enantiomers, (+) and (-)ipsdienol. The production of ipsdienol enantioruers was measured from individual, live-trapped male beetles in the laboratory. Although there was a significant regression of the blend that male beetles produced and the blend to which they responded, the sex ratios of beetles responding to different blends of enantiomers in the field did not differ significantly. In a second experiment, male-female pairs were sampled in the field, females were assayed for preference in a laboratory olfactometer, and male enantiomer production was measured in the laboratory. There was a significant correlation between female preference and male blend production. Pheromone production and response were not correlated with body size, nor was body size correlated in male-female pairs.