Garlic Mustard, an invasive plant in Vermont, has started to poke its way up through the leaves. This plant poses a risk for butterflies in the White genus (Pieris), which are tempted to lay eggs on it despite its chemicals slowing caterpillar growth and often outright killing them. But some species are less affected than others.
Which of these butterflies is the (slightly) more resilient, Mustard White?
Click below to reveal the answers to this weeks’ quiz.
The butterfly on the right is the Mustard White. The butterfly on the left is the early season, West Virginia White.
One of the reasons Mustard Whites are (slightly) less affected by Garlic Mustard is that they have a wider range of potential host plants including Toothworts, Bittercresses, and Rockcresses. The West Virginia White is restricted to our two species of Toothworts – Cut-leaved Toothwort and Two-leaved Toothwort. Mustard Whites have also shown slow adaptation to Garlic Mustard toxins but with crashing populations, evolution may not be acting fast enough to save them.
In the early spring, the Mustard White has darker grey veins that help distinguish them from the all white or faintly veined West Virginia White. The summer generation of Mustard Whites will no longer have the grey veins.
The West Virginia White is out in Vermont from the end of April (visit a patch of Toothwort near you starting next week!) and the beginning of June. The Mustard White emerges around the same time but will be around until the end of September.
Mustard White by Bruce Cook (iNaturalist)
West Virginia White by Kent McFarland (iNaturalist)
Ready for the next quiz? Click here!
