Morphological variation in the pine bark bug Aradus cinnarnomeus Panzer was studied by making 43 metric measurements of the head, thorax and abdomen of adult males and 40 of the females (n = 1884). The amount of individual variation in males and females was studied both in pooled bug material and separately in two parapatric alternate-year cohorts, i.e. in the Finnish eastern even-year and the western odd-year reproducing populations. The first three dimensions in a principal components analysis accounted for 36% of the variation present in males in the pooled data and for 43% of the variation in females, respectively. There appeared to be different trends in individual variation within the western odd-year cohort and within the eastern even-year cohort. The first principal component describes the general size of the bug in all analyses, while the second and third components correlate best with different measurements depending on the sex and the cohort examined.