Cotton-chested Yellow-neck Bee

Size about 10mm. Flying slowly with its hind legs visibly dragging. Landing on artichoke plant that hosts a lot of other insects at the moment. I am absolutely lost with this identification. Maybe it is safe to say family Apidae or at least Hymenoptera. Its hind legs are very obvious: massive and wide. I think it is mainly the tibia that is enlarged. But also the other legs and leg parts are well built. Chest looks like cotton and is hairy white. Top of thorax is black with grainy, shiny surface. Head with large, wasp-like lateral compound eyes and three oculi at the top (as usual). Maybe the identification is obvious and I simply don't see it. Last photo: some colours desaturated because a green leaf was blocking the view. Update 20/10/2016: I moved and renamed this species from Cotton-chested Apoid Wasp into Cotton-chested Yellow-neck Bee, based on Deb's feedback that it is Tetragonula. It certainly matches a few individuals in the Sugarbag Bee gallery at the moment. I might move them here at a later stage. The numbers of this species have picked up dramatically after winter.