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Butterfly Forecasts for Central Iowa  
  March and April, 2019  
  Red admiralThis is the tenth year for butterfly forecasts on my website.  It has been for the most part an enjoyable task to put them out but sometimes I struggle to keep the forecasts fresh and new.  March can be especially problematic.  It is a great thrill to see the first butterfly of the year, and that almost always happens in March.  That butterfly will probably be one of two or three species.  It will either be an eastern comma or a mourning cloak.  Sometimes it will be a red admiral. 
This year looks to possibly be an outlier.  The huge piles of snow outside as I am writing this suggest to me that the butterfly season will be late this year.  We might not see any butterflies in March this year.  So I am combining the forecast for March and April this year.
The snow is starting to melt and it might be mostly gone by the end of the month.  The butterfly season will start slowly and probably late, but it should progress rapidly once it starts.
 The butterflies which spend the winter as adults will show up first.  These include eastern comma, mourning cloak, and gray comma.  Then some of the migratory species show up--red admirals and American ladies.  Then, often by mid-April, cabbage whites and black swallowtails can be seen.  Azures can often be seen by the middle of the month as well.  It is unclear whether what we see are a first generation of summer azures (which have multiple generations), or spring azures, which have a single generation.  The whole situation with azures is confusing as there seem to be several species nationally, and those individuals have very subtle differences.  Whether those differences are big enough for the individuals to be considered different species is not clear, nor is the question as to what we have here.
Targets:
In order to change things up a little bit, I thought I would add a discussion of what I am calling "targets."  Targets are simply things that seem to be worth looking for.  The term might include rare butterflies but it might also include other creatures.  It might include something I have seen before, or it might include something I am hoping to find (or for someone else to find) that may or may not actually be found in Iowa.  It might also be some particular area that is worth searching in.  Three targets I have for this month are Henry's elfin, Olympia marble, and yucca giant skipper.
Henry's elfin:
Henry's elfin is a small hairstreak.  It is found only in some of the counties in the southern third of the state.  In Iowa the only host plant for the butterfly seems to be redbud.  Like several of Iowa's other hairstreaks, this butterfly seems to only have one generation per year.  In the case of Henry's elfin, the adult butterfly is only found for about a week each year.  The last week of April and the first week of May seem to be the time frames with the most records.  I have spent a lot of time unsuccessfully looking for Henry's elfin.  But while much of my searching was in vain, I also was lucky enough to find them on a few occasions.  A couple of times when I found them I found quite a few, and in locations where I had not expected to find them.Henry's elfin  Specifically, if you spend enough time hanging around redbuds sooner or later you will see the small brown butterflies flying around them.  The problem is that often you will not see them close up.  When I have looked for them this way I have only seen one or two at a time.  A couple of other times while walking along trails I saw quite a few of them.  They bask on the stems of brush or weeds a foot or two above the ground level, and they fly out and chase other individuals of the same species that get close.  I did not observe mating behavior, and the impression I have is that this is male on male aggressive displays, but I can't say for sure.  In spite of respectable numbers I saw on one occasion, the following week when I visited I saw none.
Olympia marble:
The Olympia marble is similar to Henry's elfin in that it might be more common than it seems to be.  It has one generation per year and only flies for a short time.   However, there are not as many recent records for the species as there are for Henry's elfin.  There is some thought that the Olympia marble has been extirpated from much of its range in Iowa, although it has been seen a few times   Most records for the species are in the western loess hills counties and a few counties in north eastern Iowa, although I do know of an individual who reported seeing them in The Ledges State Park, and even in Ames.  I have yet to see it, but I hope to sometime.
Yucca Giant Skipper:
A few years back Tim Orwig sent a message to the Iowa Insects list serve, asking if anyone in Iowa had looked for the yucca giant skipper.  It has never been found here, although it ranges widely across the United States.  Its host plants are various species of yucca, and the larva are root borers of the plants.  A link to a video by Dr. Andrew Warren, explaining some of the habits and a way to search for the species was included in the original email.  It can be found here
It is difficult to say when the adult would be seen if it is found in Iowa, but middle or late April might be a good guess.  I have looked for the adults, and have also looked at yucca plants to see if I can see any evidence of the larval feeding tunnels, but have not had any luck.  I am not prepared (or advising anyone) to break open the plants to look for the larva, but it might be interesting if someone could. 
I know some of you have already been out in the field.  Good luck looking for butterflies, and report them to the Iowa Insects list serve, the Iowa Butterflies facebook page, or Jim Durbin's Insects of Iowa site if you see some.
 
  banded hairstreaks