Studying those flowers (looking for bugs on them) I soon noticed little injuries on the upper part most of the drooping flowers. The culprits were obvious too: bees were chewing through the side of the flower's throat to get to the nectar, instead of laboriously crawling into the flower. Easier on the bees, but of course this way, the flowers were probably left unpollinated. The bees that I observed were all of one species in the genus Colletes.
|Colletes sp. bee chewing into the side of the flower to get to the nectar|
|middle: Colletes bee. right: damaged flower; left: moth|
|Moth Caloreas apocynoglossa|
The bees may be armed with a painful sting - at least in comparison with a helpless moth. Predators would avoid bees and moths. So this would be direct Batesian mimicry.
But solitary bees are not usually heavily defended and many birds feed on them.
Another possibility is that the moth gains some protection from its head-down orientation: Flycatchers tend to grab their prey by head and thorax, in this case the pretend-bee-thorax - so the moth may be able to escape from the misdirected attack with minor hind-wing injuries (same idea as in hairstreaks).
But: If the relationship between bee and moth is old and established enough to have resulted in adaptive changes in behavior and pattern of the moth, it may be save to assume that the relationship of this Colletes species and Mertensia macdougalii is even older and that the bees are specialists. Too bad for the plant then, that these bees are specialized thieves!
Quoted: Thee Bees in your Backyard by JS Wilson, OM Carril, Priceton University Press 2016