Morphometric differences between 60 specimens of Hydrobius. a Differences between morphotype and effect of body size on paramere length. Both axes are in logarithmic scale. Independently fitted lines for each morphotype are shown, slopes not significantly different. Type specimens of H. f. subrotundus and H. f. rottenbergii are labeled b Box- and whisker-plot showing differences between morphotypes on the ratio length of paramere / length of penis. Top and bottom of boxes represent first and third quartile; dark bands represent the second quartile (median); whiskers show the maximum and minimum values not including outliers (white points). Black points represent type specimens.