Vanessa Invasion

If you’ve set foot outside in the past couple of weeks and found yourself in the vicinity of any flowers, you have probably noticed an abundance of medium-sized, orange and black-colored butterflies swarming sedums, goldenrod, asters, and just about any other flower they can find.

These are Painted Lady butterflies, (Vanessa cardui), a migratory species that has begun its return trip to Mexico and California as its more famous counterpart, the Monarch, will begin in a few weeks. Also similar to the Monarch, the Painted Lady have multiple generations each summer before returning to their overwintering grounds.

Due to favorable conditions earlier this year, the Painted Lady population has exploded, increasing drastically through each generation over the summer. At Reiman Gardens in Ames, their regular count from last year tallied around 20 individuals, but this year the number exploded to 747 individuals.

Why does the Monarch population struggle year to year while other butterflies thrive? It is the old story of a specialist versus a generalist: where Monarchs utilize only a single type of plant – milkweeds – as hosts for their caterpillars, Painted Ladies are not nearly as discriminating and may use any of over one hundred different species as hosts.

In addition, habitat loss has struck Monarchs particularly hard and left them with a very small overwintering patch in Mexico, where they are vulnerable to winter storms. Painted Ladies, with a range throughout much of the globe, are better able to withstand occasional local disasters as their population is not centralized in any single place.

Originally published on Sycamore Greenway Friends