Banded Small-headed Fly

Cute little fly that looks like a bee. Maybe 6-7mm in size. It was clinging to a branch of our Grevillea bush. Next to its small head, it has very obvious white bands around its abdomen, a bit covered on top by black triangles. Body is hairy. Legs are long and black-orange interchanging colour. I am reading that its larvae are parasite in spiders.