Effects of male body size on mating activity and female mate refusal in the yellow-spotted longicorn beetle, Psacothea hilaris (Pascoe) (Coleoptera: Cerambycidae):: Are small males inferior in mating?

In the yellow-spotted longicorn beetle, Psacothea hilaris (Pascoe), variation in body size is conspicuous, especially in males. Size-related difference in male response to females and dummies treated with female extract were examined in the laboratory. Smaller males more frequently located and mounted females than did larger males when introduced to females. Smaller males responded to dummies treated with lower doses of female extract. This result indicates that small males were more sensitive to female sex pheromone and more active in their mating search and pre-copulatory behavior. However, females preferred large males to small ones. They displayed mate refusal behavior to small males much more frequently than to large males. A higher sensitivity to sex pheromone and subsequently higher copulatory activity in small males may compensate for the disadvantage of lower female choice. This hypothesis was supported by a field investigation: body size distributions were not significantly different between mounting males and solitary males.