This is a male scorpion fly. Apart from the genital capsule at the rear end (which gives it the common name of scorpion fly) it looks pretty much like the female scorpion fly.
This is a close up of the genital capsule.
Males are much more difficult to find than females. I'm not sure why this is. It could be that there are just fewer, or perhaps they are more wary, or maybe they do not live long after mating. They are also more difficult to catch.