Wander around K-Country and you’ll find two very similar, but different, little Blue Butterflies. One type is Idas Blue, Plebeius idas (formerly known as Plebejus idas or Lycaeides idas). But we find the most common to be the Silvery Blue (Lycaeides argyrognomon). Both are small, with a wingspan ranging from 22 to 30 millimeters (0.9 to 1.2 inches).
Similar but different
While both are little and blue, they have distinct differences in appearance. The Silvery Blue males typically have blue upper wings with a silvery-white sheen and black borders. Females can vary in color, ranging from light blue to brownish-gray. On the other hand, the Idas Blue males have blue upper wings with dark borders and black spots, while females exhibit more varied coloration, ranging from blue to brown, often with orange or red submarginal spots on the hindwings. Compare the top photo of the Silvery Blue, with the spots on the Idas Blue at right.
Habitat & Range
The Silvery Blue and Idas Blue also have differences in habitat preferences. The Silvery Blue can be found in a variety of habitats, including meadows, grasslands, woodland edges, and even urban areas. The Idas Blue is often associated with alpine meadows, grasslands, and open areas near treelines in mountainous regions. A general rule: the higher in elevation you go, the more you’ll likely find Idas Blues.
The Silvery Blue has a broader overall range compared to the Idas Blue. The Silvery Blue is found across much of North America, including parts of the United States and Canada. The Idas Blue, is more commonly found in mountainous regions, including in parts of western Canada and the United States.
Both generally prefer areas with suitable larval host plants and nectar sources. Both butterfly’s life cycle consists of four stages: egg, larva, pupa, and adult. The female lays eggs on host plants, which are usually legumes like the Milk-Vetches (Astragalus species, pictured at right) or Locoweeds (Oxytropis species). The larvae feed on these plants. The adult butterflies feed on nectar from various flowers, such as asters, daisies, pussytoes and clovers.
See some more of the pretty critters and butterflies of K-Country here.
