Singapore Rhododendron (Melastome malabathricum) is a weedy shrub with showy pinkish flowers. Details of the flower parts and some of the fauna associated with the plant have been posted earlier HERE.
Most of the time we are aware of the large Carpenter Bees (Xylocopa spp.) visiting the flowers for the nectar and pollen. The image at the top and the video clip above show X. latipes landing heavily on the flowers. By then pollen grains would have covered its body, shot out from the open pores of the anthers (below) as the result of the high pitch generated by the rapid flapping of the wings LINK.
This is “buzz pollination”. Once the bee returns to its burrow, it will groom the body to collect the pollen.
There are also other smaller bees hovering around the flowers. The slender bees are the Asian Hive Bee (Apis cerena) (above left, video below)…
…the bulkier ones are the Halictid or Sweat Bees (Anthophora zonata, Family: Halictidae) whose body is black with broad bluish-green metallic banding (above right, video below). As these are smaller bees, they land on the flower and move around the anthers for the pollen. As the anthers liberate the pollen grains through their terminal pores as noted above, these two smaller bees must similarly indulge in buzz pollination, as seen in the Carpenter Bees.