The images show a tiny fly perched on the filament of a flower next to the stamen, with a regurgitated droplet of nectar. Within the droplet is an inverted image of a background flower. Insects that drink nectar such as flies, bees, wasps and the like use this mechanism to concentrate the nectar they’ve collected by evaporating water from it. This produces more nutrient rich nectar and a lighter load for the insect. It’s always worth a closer look at winged insects sitting quietly amongst foliage to see if they are blowing nectar ‘bubbles’ like this.