Coloration and pattern variation in barred grass snakes. A Typical Natrix helvetica helvetica with pronounced side bars and contrasting head pattern; Röttgen near Bonn, North Rhine-Westphalia, Germany (photo from iNaturalist, Santiago Jaume-Schinkel). B Aged N. h. helvetica with faded light occipital collar and weak side bars; Hofheim am Taunus, Hesse, Germany (photo from iNaturalist, pfadfinder). C N. h. helvetica with uniform body coloration and small side bars; Gengenbach, Baden-Württemberg, Germany (photo from iNaturalist, Corinna Herr). D N. h. sicula with faded light occipital collar, small side bars and spotted body pattern; Bichlersee, Bavaria, Germany (photo Frank Glaw).