A detective story - the stalking fly
Spotted this fly taking an amazingly close interest in what a potter wasp was up to. The wasp was searching for caterpillars on my potentilla bush. The fly would follow the wasp in the air about 15cm behind it but when the wasp settled to search for caterpillars the fly would land about 10cms away and watch it.
Seems likely the fly is Amobia signata a cleptoparasite of solitary bees and wasps. If the wasp finds a caterpillar the fly follows it back to the nest and when the opportunity arises, lays an egg in the nest.
The fly and wasp
The wasp searching for caterpillars
The fly and wasp (focus stacked)