Showy milkweed is the favored plant of the Monarch butterfly, Danalus plexippus. This is the northernmost area expected to host that amazing butterfly that migrates in sequential life cycles from Mexico in February. The egg hatches and the larva metamorphases into an adult in three weeks during northerly migration. The adults lay eggs on the leaves upon which the larvae feed.

A yellow swallowtail butterfly rests on this showy milkweed plant, Asclepias syriaca, along the trail on the McNary NWR.

Viceroys (Basilarcia archippus), Monarch mimics, are also thought to acquire the bitter taste from feeding on the milkweed flowers.

The Viceroy, Monarch, and swallowtail butterflies are found on the refuge and in other areas nearby.