At my father in law’s house in Wales this summer, I was fascinated watching these robber flies at work. Stationed at the edge of a blackberry leaf they waited until an ordinary fly came close and then pounced. Wrapping their legs around it, they held the fly tightly as it struggled and fluttered. Some broke away (or were they, perhaps, allowed to go?) But I never worked out what these bandits were up to. Laying eggs? Trying to kill?