Silvery Blue (Glaucopsyche lygdamus) is a small butterfly, with a wingspan of 0.875 to 1.25 inches. Adults can be seen in our local area in March and April. Numbers peak in March. Host plants include several plants in the Pea family (Fabaceae): Vetch (Vicia), Lupine (Lupinus), Trefoil and Deervetch (Lotus), and Milkvetches (Astragalus).

It was added to the Garden’s species list only in March 2026. It is not expected to be seen in the Garden very often.

Like Gray Hairstreak and Acmon Blue, Silvery Blue caterpillars have a mutualistic relationship with ants (both species benefit). The ants protect the caterpillars from predators in exchange for the sweet “honeydew” the caterpillars secrete from a nectary gland. Roughly three-fourths of butterflies in the Lycaenidae family have a relationship with ants, but not always mutualistic. This butterfly overwinters as a chrysalis.

It is found across the Western half of the U.S., as well as the northern part of the Eastern half, and along the East coast south to Georgia. There are scattered sightings in Alaska and Nova Scotia.