Mating attraction by Stenotus rubrovittatus (Heteroptera: Miridae) females and its relationship to ovarian development.

Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae) causes brown or black marks on rice, Oryza sativa L., grains (pecky rice), and it is becoming of increasing importance in Japan. Attractiveness of adult females or males of S. rubrovittatus to conspecific individuals was examined in the field in 2003 and 2004. Unmated female-baited traps captured significantly more males than did the unmated male-baited traps. However, the numbers of females captured by female- or male-baited traps were low, and they were not significantly different from the numbers caught by the control traps. No nymphs were captured by any traps. In 2004, we examined the effects of age and mating experience on female attraction ability with the goal of understanding the role of reproductive development in the observed behavior. The daily number of males captured by young unmated female (3-d-old)-baited traps increased from the first day until the fourth day of experiments, and then capture started to decrease. The peak in the number of captured males corresponded to the preoviposition period. When we observed ovarian development of S. rubrovittatus females under 25 degrees C and a photoperiod of 16:8 (L:D) h, we found that vitellogenesis had already started in approximately 30-50% of 1-d-old individuals. By the fifth day after emergence, 50-70% of individuals had mature eggs. These results indicated that the attractiveness of females is the strongest when egg laying becomes possible. Therefore, S. rubrovittatus females attract males selectively for mating, and it is probable that females use a sex pheromone for the attraction.