Thanks @CathB ! I thought of beetles initially but changed my mind when I saw the hole in all of them. It being a parasitic wasp hole makes more sense! I've reared Cadmus before and these are smaller and consistently very dark brown all over. I guess they are mimicking drops of sap because they look very similar.
Hi @Hejor1. This might be the pupal case of a leaf beetle. See for example sighting 4411148. The round hole would probably have been made by an exiting parasitic wasp. The beetles usually neatly remove the top of the case. See sighting 4496734.