The weather has turned cold and the butterflies are likely gone until spring. Now is probably an odd time to think about butterfly habitat, but it has been on my mind.
Iowa is mostly rural. In fact, according to the Iowa State University land use data, 91% of the land is in farms. Just under 75% is “crop”, which I assume is mostly row crops–corn and soybeans. Unincorporated/roads come in at just under 2%. Pastureland is 4%, woodland closer to 3.5%, “house lots, ponds and roads” comes in at around 4.75%. (All except the unincorporated/roads are subsets of “farms.”
I think the land classified as “crop” is not habitat for butterflies at all. Prior to the development of herbicide resistant crops it might have been marginal habitat–milkweeds, asters, smartweeds, and others living within the rows between corn and beans.
So the ditches become butterfly habitat. What kind of habitat is this?
This is an area near our house–there are grasses and flowers along the side–not all that diverse, but along the edge there are asters and hoary vervain.
How about this area? It has been mowed, but probably only once or twice per season.
How about this area? This photo shows one of the problems that might be encountered if you tried to manage roadside ditches for butterflies–that is, who manages them?
Ditches are managed by County or State departments of transportation–that management is usually fairly minimal, and intended only to ensure the safety of people using the roads. Adjacent landowners also can manage the ditches–usually by mowing, and usually to satisfy their own aesthetic view of how the ditch should look. In some places right-of-way ditches have allowed harvesting of crops–usually hay.
Roads are not just rights-of-way for transportation. In the photo above, there are other utilities–underground telephone lines, I think. So different utility companies might manage the vegetation in those areas.
Habitat is greatly affected by the management of the ditch, and ownership of the management can belong to more than one party.
There are programs in Iowa that try to improve the habitats in roadside ditches. Without that special management, the ditches are probably fair to poor butterfly habitat.
The roused bear 
In some states those ditches and roadsides are managed as wildflower habitat — which helps the butterflies. Even Texas does that. It’s a drive started by Lady Bird Johnson.
Tennessee used to have a model roadside wildflower habitat management program from the years when Lamar Alexander was governor. They discovered that they could increase tourism, reduce mowings, and improve the water and soil conservation properties by managing for flowers.
You might check with Iowa’s highway department and see if they have a clue. The Ladybird Johnson Wildflower Center in Austin may have some people on staff who could advise you on changing policies, and, if necessary, laws.
Yes, we have that here, also–they call it integrated roadside management. But it is a huge task and is mostly only done in areas with high visibility–for example, the interstate system.
At our most recent iowa honey producers convention, Joy Williams from the IDOT spoke about revegetation programs on Iowa’s state highways. Plants are chosen for year-round appearance rather than for insect habitat.