Each year on the first Saturday in May, National Start Seeing Monarchs Day raises awareness to preserve the Monarch butterfly and prevent it from being added to the endangered species list. The Monarch Butterfly is the State of Illinois’ official state insect.
The monarch (Danaus plexippus) was chosen in 1975 to be Illinois’ State Insect.
https://nationaldaycalendar.com/national-start-seeing-monarchs-day-first-saturday-in-may