Hundreds of dead flies in garden
This summer I've noticed that the south side of my garden has been inundated with what look like green bottle flies. They seem to be very attracted to the milkweed. Unfortunately, I'm finding clumps of dead flies on the milkweed as well as on the tips of all my other plants. At first they appear to be sitting/resting on these plants but when I take a closer look, the flies are dead. I've attached a few pictures for reference. I'm not sure if this has anything to do with the milkweed, but this is the first year we've had an abundance of it and the first year we've had this issue with the flies. The little bit of information that I've found online, that may be related, points to a fungus that entices, kills, and decomposes the insects. Nonetheless, any help in determining the cause of this strange phenomena is welcome.
Hennepin County Minnesota flies
Green bottle flies are attracted to decaying matter: manure, dead critters, even dead plants. I'd look for such things near where the flies are congregating:
Their lifespan is short, so they may be gone by the time you read this.