Another ecology question this week – this time about how butterflies avoid predators!
The two butterflies below have a relationship based on mimicry. One butterfly is poisonous and the other is harmless but has evolved a similar color pattern to the poisonous one to confuse predators.
Which of the butterflies below is the edible mimic?
I love this one. I hadn’t realized that “distasteful” bit. How fun this has been!!
Click below to find out the results of this weeks’ quiz!
The Red-spotted Purple on the left is the mimic!
The Pipevine Swallowtail on the right is poisonous. Caterpillars keep acids in their bodies from the pipevines they feed on. These acids are later turned into poisons that make them unpalatable to predators. The Red-spotted Purple feeds on harmless trees like willows, aspen and yellow birch.
So, Why do they look alike?
The Red-spotted Purple is a Batesian mimic of the Pipevine swallowtail, which is the term for when a harmless species evolves to use the color markings of a poisonous species. Adopting this coloration can trick predators into thinking that the harmless species is also poisonous.
Pipevine Swallowtails are rare in Vermont since they prefer warmer climates and need plants in the pipevine family, which do not grow natively here. But as temperatures warm and pipevines are planted in gardens, the range of the Pipevine Swallowtail has expanded into VT and NH. The Red-spotted Purple is also typically found in southern climates but the species is very abundant in Vermont. This is because the Red-spotted Purple is a color-morph subspecies of the White Admiral. While 61 Red-spotted Purples have been recorded in Vermont on iNaturalist, over 1900 observations were recorded of the White Admiral. Why the disparity? In southern climates where the species overlaps with the Pipevine Swallowtail, mimicry of their blue colors is selected for but that pressure doesn’t exist in the north, leaving the white striped color morph we are more likely to see. Don’t be surprised if you see some confusing color patterns – there is a high rate of hybridization when the two populations overlap.
Red-spotted Purple by steve b (iNaturalist)
Pipevine swallowtail by Robert Creech (iNaturalist)
Ready for the next quiz? Click here!
Glad to hear that it has been fun and that you’re enjoying the biology/ecology facts of butterflies as well!
