Suddenly there were thousands of them. It was, in biologists’ terms, an irruption, a sudden sharp increase in the relative numbers of a population. My grandpa’s eyes had never witnessed such a dramatic increase. Unusual things like these a naturalist remembers and records. My experience has recorded nothing of this magnitude before. It may be a lepidopterist’s dream come true.
You ask what “irrupted”? You may be questioning the use of the word. The word irruption is not a mistake, the term is not “erupted”. An eruption is for volcanoes, and rashes. Our subject is an irruption of butterflies. The sudden appearance of thousands and thousands of Painted Lady butterflies (Vanessa cardui) to be specific.
As this holiday weekend began we had the privilege of traveling with 4 grandchildren across half the state of North Dakota to connect them with their cousins for a time with family. It is nearly 200 land miles, or 3 hours of driving time. On the outbound trip, there were thousands of painted ladies crossing the road headed south, likewise on the return trip. Even more astonishing, the return trip was 3 days later. How many butterflies flew southward during the time we were with family? When we returned there were still thousands flying. All were southbound. Arriving home last evening, we found dozens on the flowers of our postage stamp sized prairie. Today my 11 AM estimate was 40 butterflies. Most years there are 3 or 4. The large number is highly unusual, but within normal for the painted lady butterfly. From season to season, this butterfly has noticeable population increases and declines. The current irruption is massive and impressive, the largest in memory!
During these times of irruption, thousands to millions of individuals can be seen. Since they migrate close to the ground, just 6-12 feet above the surface, they are easily noticed. Most of the world’s population has had opportunity to see painted Lady butterflies since they are found on every continent in the world except Australia and Antarctica. Many painted ladies migrate from the south in spring before the more well-known migrator, the monarch butterfly arrives. Perhaps one reason painted ladies are found in almost all parts of the world is their ability to feed on many different types of plants. Few other butterflies will forage on such a wide range of flowering plants. Over 100 have been recorded. The painted lady butterflies in the photos were feeding on Cup Plant (Silphium perfoliatum) flowers. Possibly a second reason there are so many painted ladies in our prairie garden is the great abundance of cup plants growing there. Painted Lady butterflies prefer composite flowers that are tall. Cup plant grows tall. The plants in the prairie garden tower more than 10 feet in height. Go ahead try to imagine dozens of painted ladies on tall yellow flowers. They too are pollinators, while they seek food for life, the plants they feed on are able to develop seed from the mix of pollen moved by butterfly feet, proboscis, and even wings.
From egg to prickly caterpillar, to chrysalis and on to adult, the painted lady really lives a life of mystery. There have been thousands of words written, hundreds of websites produced and thousands of school children studying the painted lady. Yet, it lives its life largely away from human attention. Most humans are unaware of the wildlife that lives just outside their homes. The coming change of season will move the painted lady butterflies to their winter places. It is why they are moving now. In spring the mystery is continued. It is reversed, painted lady butterflies will move northward.
The greatest naturalist the world has ever known was King Solomon. He spoke about plant and animal life to the kings of the world at the time. Solomon also reminded us that there is a God directed time for everything. He said, “There is a time for everything, and a season for every activity under the heavens…”
This is the season of the painted lady.