The width of a plot was 1 m; the length ranged from depending on the distribution of plants; and the distance between nearest plots was greater. Almost all plants within the census plots were individually tagged each year, but plants that formed highly dense patches were excluded because the discrimination of individuals was difficult. After tagging, the rosette diameter was measured for each plant prior to the flowering season in 2006 to take plant size into account in our statistical analysis of fitness differences between hairy and glabrous plants. We used 202 hairy and 262 glabrous plants in 2005 and 160 hairy and 199 glabrous plants in 2006 for analysis. The number of herbivorous insects on each plant was counted once a week on sunny days during the flowering season, which represents the period in the year when herbivory by leaf beetle larvae was most intensive. The damage on leaves was estimated by eye and categorized into one of four levels: 0, no damage; he total possible area of leaves consumed; 2,,50% possible leaf area consumed; possible leaf area consumed. The presence or absence of damage on the apical meristem was also recorded. We adopted this estimate of damage because the rapid loss of leaf tissues due to intensive herbivory did not allow a quantitative measurement to be made. Fruit production was determined at the end of the flowering season. We did not examine seed production because seeds were spontaneously released from mature fruits, and it was difficult to prevent seed release from fruits while allowing herbivores access to SCH727965 supply flowers and young fruits. Seed production and male fitness were Nutlin-3 in vivo likely to be strongly correlated with fruit production in the study site because P. brassicae consumed flowers and flower buds, resulting in the simultaneous loss of both male and female reproductive organs. We also examined the abundance of herbivores once or twice per month during the summer through winter seasons and found that the intensity of herbivory was weak and negligible. Thus, we present the results only for spring herbivory by P. brassicae larvae in this report. To examine the costs and benefits of trichome production, we conducted field transplant experiments in which the intensity of herbivory was manipulated using insecticide . A. halleri subsp. gemmifera reproduces in spring and grows vegetatively in the rest of the year, and P. brassicae was active from spring to autumn.