These are flies from the Bombyliidae family of insects. They are a large family of flies and their life cycles are not well known to many studying these insects. They generally feed on nectar and pollen and thus pollinate flowers as they go along. They have an unusually long proboscis used to suck out nectar from the flowers. These bee-flies don’t have stingers, but they look like bees and this helps protect them from predators.