A closer view of the dead honey bee with flies. As mentioned in the next photo, this bee died, trapped, on a milkweed flower. Bug Guide thinks the flies may be in the Genus Desmometopa, the Freeloader Flies, and they note that: "Females are kleptoparasitic and are especially attracted to predatory insects or spiders feeding on honeybees". So there may have been something else feeding on the bee that I didn't notice and scared off when I picked it up. You can see how small the flies are compared to the bee.