This is the female of the violet (or bluish) oil beetle (Meloe violaceus). Spot reads that this unusual beetle lays its eggs on the ground in leaf mould (as here). These hatch into long legged small larvae (triungulins) that swarm over plants in hot weather (they may have to wait a long time this year). They then attach themselves to a wild bee and are carried back to the bee's nest where they set about devouring the eggs and grubs. As they change into grubs themselves they eat the honey. They pass the winter as fat headless legless maggots then metamorphose one last time and crawl out in the Spring as adults to feed on buttercup plants. They also act as models for Alien. When picked up or otherwise irritated by inquisitive dogs they exude a foul fluid from their joints. They have overlapping wing cases. This one is distinctly blue.
