Perhaps like you I have been noticing lots of white butterflies dancing in the breeze in the road ditches over the past couple weeks. A closer look would reveal that most of them are white with perhaps some tinges of pale yellow, a couple dark spots on the wings, and some amount of darkening on the wing margins.
Based on what I have been seeing, most of them are cabbage butterflies. As the name implies, cabbage butterflies are closely associated with cabbage and other members of the mustard family because the larvae or caterpillars use these plants as their main food source, but they are not considered a serious pest of the garden and agricultural mustard crops.
Cabbage butterflies produce several broods over the summer, and their numbers generally peak about this time of year. Ron Royer, entomologist and science professor at Minot State University notes in his book Butterflies of North Dakota, that cabbage butterflies are the species most likely to be decorating the radiators and grills of our vehicles this time of year.
It may surprise you, but the cabbage butterfly is not a native species. Royer notes in his book that the cabbage butterfly was introduced to Quebec in the 1800’s and has since spread across much of North America. As occasionally happens with other introduced species, the cabbage butterfly has been displacing some of our native species.
We are also likely seeing some clouded sulphur butterflies and alfalfa butterflies. At a distance they can look similar to the cabbage butterfly. Both species are common across the state, and feed on members of the legume or bean family. They can be expected to be seen more frequently in and around lots of alfalfa and sweetclover, or perhaps red and white clover.
As far as I have been able to determine, the alfalfa butterfly is native to North America, but before introduction of alfalfa the butterfly used native legumes. Now of course the widespread planting of alfalfa and clover has provided much more habitat for the species than was available historically.
Take a few minutes to enjoy these butterflies. These species are providing us with perhaps the best butterfly show of the year. Enjoy them while you can, because as we all know, they will not be around much longer!
Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.