I have been watching the milkweeds for hairstreaks lately, and have seen one banded hairstreak and a number of corals. I came across this one more or less by accident. This butterfly is not rare, but it is not common, either. It has one generation per year here in Iowa, and adults can only be found for a week or two.
It is on dogbane, which is a relative of the milkweeds.
The roused bear 
We used to see a very similar butterfly to this one in Spain, called the Blue-Spot Hairstreak (Satyrium spini) – not very imaginative, but does the job…
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