...also notice the apical lunule (the white band at the very back tip). It always has that distinctive shape in punctulata... it's a very thin band that runs completely across the bottom and then abruptly bends in at a sharp angle at the top into a little knob.

Also the body shapes of the two species are very different. C. punctulata is a lot more 'athletic' looking, with a narrower body, and narrower pronotum with a more cylindrical shape. punctulata also has very few hairs (setae) on the top the head, whereas duodecimguttata is pretty hairy. Although that may be hard to tell from a photo...

Dan

This is punctulata. Look for the row of punctations along the inner border of the elytra.