Here’s a butterfly that’s relatively easy to see this time of year. The Common Wood Nymph or Cercyonis pegala is generally dull brown but it has some snazzy highlights that make it stand out.
First of all, take a look at this butterfly’s legs. Specifically, count them. What’s going on here? Aren’t all insects supposed to have six legs?
In fact, butterflies in the Nymphalidae family are known as “brush-footed” butterflies. That means their first set of legs has been reduced over time to something that looks like a tiny pipe cleaner, and resides near its mouth. Those brushy feet act as taste organs near the head, and the remaining four “normal” feet also have sensory hairs to find food. So do they or don’t they have six feet?
In addition to the unique organs for tasting, Cercyonis pegala have interesting organs for hearing: A swollen area on the front edge of the forewing houses a sensor for picking up vibrations, particularly the low sounds of bird wings.
Common Wood Nymphs have two large eyespots on their forewing and may have several smaller spots on the hind wing. The coloration and size of the spots and the wings may vary widely. There are three or four Cercyonis species in the U.S.
These fairly large butterflies like to be in open grassy areas, and should be visible through September. My photo of the mating Common Wood Nymphs isn’t great, but it illustrates how awkward they look while they’re mating. They flew (badly) and then landed several times as I tried to take pictures.
Females lay hundreds of eggs, one source says “haphazardly,” without attempting to attach them to any plants. Apparently that works, because the larvae can eat a wide variety of grasses and stems and even feed on feces and sap.
Fun fact: This species is also known as the “Goggle Eye.”
See more of Karen’s work here.
Montana field guide info on the species: https://fieldguide.mt.gov/speciesDetail.aspx?elcode=IILEPN7010
University of Colorado paper on wood nymphs’ senses: https://www.colorado.edu/asmagazine/2023/01/17/common-wood-nymphs-have-sensory-surprises-0