Looking for Swollowtale Butterflies

Asked July 17, 2020, 11:14 AM EDT

We have several butterfly bushes and other plants that usually attract many butterflies every year. We have seen none this summer. Can you tell us why? Thanks, Mary Ann

Carroll County Maryland

1 Response

Hello Mary Ann,

The multiple late frosts this year could have played a role in hampering pollinators this year - some are more resilient to cold than others once they emerge from winter dormancy. Additionally, predator-prey interactions can be at work, where some years butterfly populations boom or bust based on how well their predators (or parasitoids) have fared and how many survive to adulthood. There are naturally-occurring pathogens, like insect-infecting fungi, which may have prospered in the wet, cool conditions of this spring's weather (and the past few springs). At a broad level, the persistent background pressures of pesticide use, habitat loss, climate change, and introduced pests (both as direct competitors, pathogens, or predators, and indirect as resource destroyers) all play a role in chronic decline of pollinators and other insects.

Swallowtails are most numerous in our area in mid- to late summer, as this is their "last hurrah" for breeding before they spend the winter as a chrysalis in the final generation of the season. Magnets for attracting them - where they seem to be most noticeable - appear to be Joe-Pye Weeds and their relatives (Eupatorium), Ironweeds (Vernonia), Hyssop (Agastache foeniculum and its hybrids), Common Milkweed (Asclepias syriaca), and Beebalm (Monarda) if any are still blooming at the time. It's not uncommon in August to see dozens of Swallowtails nectaring on tall clumps of Joe-Pye Weed and large patches of Common Milkweed along the roadsides and other semi-wild areas.