One interesting spot I made this summer on my Sea holly was this Ornate Tailed Digger Wasp, Cerceris rybyensis. A first for me and I'd initially thought it a Sawfly or Ichneumon wasp. This tiny wasp hunts small to medium sized bees which are (unfortunately for the poor bees) paralysed by their sting.
That may explain the goodly number of dead bees I noticed and wondered about in late spring and early summer. The females nest in compacted bare ground, sometimes in desnse groups, which also makes sense as there is an area with bare earth from my building work that I deliberately left this season after seeing all the bee (and presumably wasp) burrows.