Observed this very colorful insect on Asclepias subulata (Desert Milkweed) in Phoenix Arizona. About 8 am, temperature about 90F, sunny, late-September. When flying it seemed to have a narrow waist like a wasp. About 5 cm long, appears rusty-red in flight (not surprisingly given its size). As the pictures show, it was enjoying a bit of nectar from the flowers. Would love to know its name so I can greet it properly next time!
Possibly a tarantula hawk (because of its red wings and metallic blue body), and because they inhabit the Southwest US. It being on the flower in the picture makes sense as “...adult tarantula hawks are nectavores and feed on flowers”. They have very painful stings, but as with most insects, if nobody bothers them, they won’t bother you.
The females hunt down and paralyze tarantulas and lay their eggs in them, hence the name. Freaky, isn’t it?