Effects of shell size/thickness and operculum on predation success of Badister pictus A relationship between maximum shell height/width and the presence/absence of an operculum and predation success (N = 155) B relationship between the shell thickness and the presence of an operculum and the predation success (N = 55). Red triangles and blue circles show snails with and without an operculum, respectively. Red and blue lines represent logistic regression lines of snails with and without an operculum derived from generalized linear mixed models, respectively (Tables 2, 3).