Blue-winged Olives
Baetis
Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
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Adams
Like most common names,"Adams" can refer to more than one taxon. They're previewed below, along with 5 specimens. For more detail click through to the scientific names.
Mayfly Species Siphlonurus alternatus
These are often called Adams.
This species occasionally produces important spinner falls. Its spinners may join the swarms of Siphlonurus quebecensis or Siphlonurus rapidus, amplifying the importance of all three species.
I'm tentatively classifying this one as Siphlonurus alternatus, because it seems to fit that species best in the old keys in Needham's Biology of Mayflies, but I'm hesitant because I can't find documentation that southwest Montana or the surrounding area is within the species' range, although they are widely distributed throughout eastern North American and western Canada.
Mayfly Species Siphlonurus quebecensis
These are often called Adams.
This is the Siphlonurus species I have encountered most frequently on Eastern trout waters. I often find its spinners swarming in a mix with Siphlonurus alternatus, and I have read that Siphlonurus rapidus may join these groups as well.
This one hatched in my house after I brought some nymphs home to photograph.
See 4 more specimens...
Mayfly Species Siphlonurus rapidus
These are sometimes called Adams.
This species may reinforce spinner flights of Siphlonurus quebecensis and Siphlonurus alternatus.