Blooming fennel is a magnet for all kinds of creatures, including this tachinid fly. At least I think that’s what it is. As with the probable honeybee I photographed a few days ago, there are thousands of varieties of these insects, and an amateur naturalist like myself does well to hedge his bets. However, this kind of fly is mentioned frequently as a visitor to fennel, adult members of this species are known to feed on flower pollen, and some tachinids look a lot like houseflies, as does this individual.
The fly doesn’t have the elaborate pollen-catching and carrying equipment of the bee, but pollen will tend to stick to its spiny legs and get carried to other flowers. Besides its work as a pollinator, several editions of the tachinid fly are useful biocontrol agents, because they lay their eggs or larvae with fatal results on other insects that destroy crops. So if you’re in the park and you see what looks like a housefly, don’t swat it. Thank it.