Glaucopsyche piasus piasus, the Arrowhead Blue, was starting its flight at higher elevations along Sherman Pass on May 15, 2014. This one was at Alder Creek, 6800' elevation. At lower elevations, and on a different lupine host, the darker subspecies excubita was flying in early to mid-April.
Moving from Alder Creek to the high meadows east of Sherman Pass, the first butterflies had already begun to emerge as the last of the snow melted. I found this perfect nominate Glaucopsyche piasus flying with two other species in the meadows: Polygonia gracilis zephyrus and Pyrgus ruralis ruralis. May 15, 2014.
An ant-attended last-instar larva on host lupines from the Alder Creek area. This was June 28, 2017; this should pupate and then overwinter at the base of the plant in that form before emerging ca. next May. Thanks to John Emmel for confirming the identification.