Watercress Leaf Beetle Phaedon cochleariae

I'm not sure how widely the vernacular name is recognised. This one (Watercress Leaf Beetle) is used at the UK Beetles website, but NatureSpot uses an alternative name, Mustard Beetle.

These two were a mating pair collected from among at least 10 similar beetles on watercress. They both seemed to key to cochleariae but the first one I examined (the female) had more-or-less entirely black antennae, the only hint of colour on segments one and two being at the very apex of each segment. Also the diagram of the male's median lobe in Duff shows a very squared-off tip, whereas the tip of the one I collected was clearly rounded. The median lobe is strongly curved so if I laid it so the basal section was flat and the apex curved up towards the camera then it did appear squared off, but surely that's not a standard way of viewing it? Anyway, other sources (including Mike Hackston's ley and the German website coleonet.de) do not show the tip squared off.

female Watercress Leaf Beetle Phaedon cochleariae showing head, metasternum, pronotal fore margin, close-up of pronotal disc, apical sternite and spermatheca, Wendling Beck Environment Project (Norfolk, UK), 1st May 2024

male Watercress Leaf Beetle Phaedon cochleariae showing metasternum, pronotal disc and median lobe (3 views), Wendling Beck Environment Project (Norfolk, UK), 1st May 2024