DIGGER BEES CLOAK AND DAGGER BEES. Thyreus himalayensis
A tiny little bee that you can often find in the butterfly gardens of Shing Mun Country Park.
Look for the more common banded digger bees, and then wait patiently and more than likely one of these will show up. These bees do not have a pollen carrying region on their legs. It is a type of cuckoo bee, a term that is used for a variety of different bee lineages which have evolved the brood parasitism behaviour of laying their eggs in the nests of other bees, like the cuckoo bird. These bees lay their eggs on the pollen masses made by other bees, the larva hatches, kills the other occupant (egg or larva) and feeds on its provisions. Rather like a hedge fund manager, or someone working for AXA.
This is called kleptoparasitism (etymologically, parasitism by theft) which is a form of feeding in which one animal takes prey or other food that was caught, or collected, by another animal. I have also read, but not seen that they can take nectar from the base of the flower by stabbing through the nectary, rather than using the conventional method of collecting nectar, and getting a dusting of pollen, so they steal their food, without pollinating the host flowers. Lovely, beautiful little bees, but quite naughty too.