A Branchine Ichneumon

Probably Lissonota coracina, found on wild angelica, Angelica sylvestris.
One of three females found on two nearby angelica flowerheads at Cullaloe Reservoir Nature Reserve.
The spike on the end of its abdomen is its ovipositor for laying eggs in the larvae of various small moths.  Adults feed on nectar.  Harmless to humans.