Galerucella sagittariae

This species is tricky to tell apart from Water-lily Leaf Beetle Galerucella nymphaeae (and the two may in fact be the same species). According to Duff sagittariae is less than 6mm long, nymphaeae is at least 6mm long - this was 5mm. Duff also has nymphaeae as usually darker brown on the elytra. For these reasons I have identified this one as sagittariae. Duff also states that the apical angles of the elytra are right-angled or only slightly produced on sagittariae and slightly produced on nymphaeae. On this specimen they were slightly produced - which I take to be ok for either species, assuming there is no significant difference between Duff's "only slightly produced" (sagittariae) and "slightly produced" (nymphaeae).

Galerucella sagittariae showing the tips of the elytra, Dillington Carr (Norfolk, UK), 14th May 2022