Those are fruitflies, most probably Dacus dorsalis aka Oriental Fruitfly. They are known to congregate in large numbers on certain plants as shown here. Identification of flies depend on wing venation, no of segments of the antennae among others. Off course, these days, a nice picture also helps. Try to get a shot with the wings in focus if you wanna really id the bugger.
Syrphid files or hoverflies are normally hovering around and normally, dont appear in large numbers together but the best way to id them is to have a look at the veins on the wings. They are also quite good at mimicking bees in shape and colors. Therefore, from the pictures, it is quite safe to eliminate them as a choice.
