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  Oarisma poweshiek
Biology of the Poweshiek Skipper
Original description
Henry's list

Oarisma poweshiek is a small, prairie obligate grass skipper butterfly.  Part of its biology is known, but there are huge gaps in our knowledge of the species.

Here is what we do know:  O. poweshiek has one generation per year throughout its range.  Adults can be found flying from mid-June to late July, with peak populations occurring at about the end of the first week of July.  The flight period lasts about three to four weeks.

Eggs are reported to hatch within 9 to 10 days.  The caterpillar goes through seven instars and spends the winter in the fifth instar.  There has been some speculation about what the caterpillar host plant is (or what the plants are).  Spike rush, prairie dropseed, and little bluestem have all been reported as possiblities.  What plant or plants are used by the caterpillars is not known for certain.

Bugguide has a photo of the egg here, and a couple of photos of the adults as well.

This butterfly is only found in prairie areas that are original and not degraded too much.  It seems to be sensitive to management of prairies by fire (as are many other invertebrate species), and does not seem to be found in reconstructed prairies.

A couple of fairly good descriptions of the life history of this butterfly can be found here and here

Unfortunately, that is pretty much all we know.  The descriptions on the two external links are more detailed, but in a sense they define what we don't know more than what we do know. 

So here are some of the problems with attempting to conserve the species.  It is very difficult to survey for the butterfly, because it only flies for a short time of the year.  If you go to a prairie and don't see them, is it because you were too early, or too late, or because they simply are not there.

Historically, the information we have about butterflies comes from collections or more rarely surveys.  Surveys tend to concentrate on what is there, not what is not.  Recent surveys in Iowa have made a point of noting what is not present in survey areas, and the news has not been good for O. poweshiek, or for a number of other habitat specific butterflies as well.

The areas where this butterfly has been found in the recent past are very small as well. One of the last places the Poweshiek skipper was seen in Iowa was Hoffman Prairie, near Clear Lake.  This is a small patch of ground, a prairie pothole area about 37 acres in area.  The picture on the left is the prairie.  The picture on the right is the Super WalMart in Ankeny.  The red squares are approximately the same size.

The actual amount of undisturbed prairie is smaller than the preserve. This is not good habitat for butterflies of any kind.

Hoffman Prairie is  typical of the other areas in Iowa where the Poweshiek skipper has been found.  It is good, relatively undisturbed prairie.  It is also geographically isolated from similar areas.  Presumably the Poweshiek skippers found on this prairie were all hatched here--the area seems isolated and removed from other known sites.  If they disappear from here there is not likely to be a source nearby that can repopulate this site.
So what problems can you face if you try to preserve the Poweshiek skipper just at this one site? Let's go through some of the issues.
1.  Is the Poweshiek skipper still found on the site? 
Bottom line is that we don't know.  Two or three individuals were seen there in 2007.  I think there was a sighting in 2008 of a single individual, but it has not been seen on the site (or anywhere in Iowa) since then.  The individuals seen in 2007 were seen as a result of a fairly extensive survey conducted that year.  There have been people, including myself, who have looked for it since then, but we have been unsuccessful. 
2.  How is the preserve managed?
To be clear with this exercise, the preserve is owned by The Nature Conservancy, and they make the decisions concerning how the preserve is managed.   Other Poweshiek skipper sites are owned and managed by a number of different organizations or individuals.  While invertebrate mangement issues are clearly discussed in a number of forums, there is no clear path to communicate butterfly conservation issues to those mangers.
That being said, Hoffman Prairie seems to be managed in a manner that should and does maintain invertebrate diversity.  I have not seen evidence of  prescribed burning on the site.  There are other butterfly species found here  that are really not common elsewhere, such as this acadian hairstreak.
3.  Is this an island?
Since there does not seem to be suitable Poweshiek habitat nearby, this area probably acts as an island.  The Theory of Island Biogeography, proposed by E.O. Wilson and others suggests that there are limits to the number of species that an island can support, and that those islands slowly reach an equilibrium as the diversity goes down.  Preserving small patches of habitat may not be enough to save the species.
4.  Are there other issues?
One year when I visited I noticed that the prairie was trying to encroach into the ditch and road right-of-way to the south of the site.  The right-of-way had been mowed.  Would it be possible to change this standard of practice for this site?  Who does the management of the roadway?  Would a less intensive mowing of the ditch make a difference?
There is a gravel road along the western border of the site.  The crushed limestone rock on this type of road can kick up a lot of dust, especially in dry weather.  What impact would that have on any butterflies or caterpillars?
Does road salt have an impact? 
5.  What impact does Iowa's agriculture have on the Poweshiek skipper?
After the apparent disappearance of the Poweshiek skipper from Iowa's landscape discussions about the cause noted a massive outbreak of soybean aphids in about the same timeframe.  Could pesticide applications to control the aphids have been a factor?  My conclusion was that yes, it could have.  In fact, the pesticide cause cannot be ruled out, and in my opinion it was the leading candidate.  I will develop a position paper on the pesticide application in the near future.
One other possible cause of the probable exterpation could be an invasive alien species.  There was a population explosion of an invasive lady beetle, probably caused by the soybean aphids, that occurred at about the same time.  Could Harmonia axyridis or some other pest be the cause?
6.  What can we do now?
If the Poweshiek skipper has indeed been extirpated from this site there will never be any certainty as to why it disappeared.  Can it be re-introduced?  Will the same thing wipe it out that eliminated it before?
7.  Does it matter?
I hope so.  Biological diversity matters.  This small butterfly matters.  And even if the task is difficult and may be impossible, it is important to continue the struggle for this butterfly.