If I’m not mistaken, this Robber Fly (or Assasin Fly) is sucking the life-blood out of one of those cockchafers in Janet’s previous post. Robber Flies are fast and agile predators and eat a wide variety of invertebrates (e.g. beetles obviously, flies, spiders, moths). Once caught, the prey is quickly killed using a hypodermic-type proboscis that injects neurotoxin-containing saliva into the victim. The saliva also contains enzymes that ‘digest the victims insides, allowing the Robber to feed on a liquid diet (rather like spiders do, too). That’s just what this fellow was doing to the hapless cockchafer when I found it. Whilst feeding, Robber Flies seem to remain motionless, focused on the job, allowing for easy photography. They’re clearly beneficial insects- though I’m glad I’m no beetle.