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Butterfly Forecasts for Central Iowa  
  May, 2022  
  Silver-spotted skipperMay can be a frustrating time for butterfly watchers.  There are always cool, windy, cloudy days--almost but not quite butterfly days.  Then you get perfect days when other obligations keep you inside.   The diversity of the butterflies on the wing is fairly high, but the overall numbers are low.  (Look at the phenology chart on this Insects of Iowa page).  The numbers rapidly increase at the end of the month and into June.  Look at the phenology charts for species like the eastern comma and the gray copper.  Eastern comma has adults which emerge from their over-winter aestivation and fly mostly in March and April, at which time they mate and deposit eggs.  There are three generations after that.  The broods sort of overlap--a butterfly you see in mid July might be from the first or second generation.  The gray copper has only one generation. Both species can be present in May, but the overwhelming numbers are present at other times.  A lot of species have a similar pattern.  You can find them in May, but there are many more in June or July or August.
As we start to live our lives outside more in the late spring and early summer, we do start to see butterflies more.  Dandelions in our yard will attract red admirals, painted ladies, American ladies, and clouded sulfurs.  If you have flowering trees you will bring in those butterflies plus eastern tiger swallowtails and giant swallowtails.
On the subject of swallowtails, the zebra swallowtail has breeding colonies on the southeastern corner of the state, in Shimek State Forest, and on the southwest, in Waubonsie State Park.  This colorful butterfly uses the pawpaw tree as its caterpillar host plant.  I have heard of efforts by individuals in this state to plant pawpaws in yards and other places in an attempt to attract zebras.  I don't know if these are formal, documented efforts or just random acts, but last year and even 2020 had a fairly significant number of sightings of this beautiful butterfly in central Iowa.  It would be interesting to see if this is a long term trend, or just short term random increases in the population size.
common sootywing If you watch closely you might be able to see some skippers.  Silver-spotted skipper is by far the largest and most showy of Iowa's skippers.  You might also see Peck's, tawny-edged, least, and common checkered skippers.  Common sootywing can sometimes be seen as well.
Eastern tailed-blues should start showing up soon.  Although they are widespread and common, and probably present in most yards they are small and easily overlooked.  The small blue butterfly you see flying around and landing on low weeds and grasses is probably an eastern tailed-blue.  If it flies up into the trees, it is more likely to be a summer azure.
You might be able to see the small hairstreak called Henry's elfin during the first week of May if you are lucky and live in an area where redbud grows wild.  There is a generation of juniper hairstreak that peaks in mid-May.  I have run across a couple of individuals of this butterfly in Dallas County, Iowa, but also spent a lot of time looking unsuccessfully for them.  They are much more common in the loess hills area.
Get outside and keep your eyes open for butterflies.  They are around now.  The numbers really start picking up toward the end of the month, though.

Harlan Ratcliff
 
  American copper  
  March-April, 2022  
  Mourning cloakSpring seems to be here now.  The calendar will make it official within a few days.  Butterfly season has started.  Already there have been a couple of sightings--an eastern comma on March 1 and a mourning cloak on March 14, both posted to the Iowa Butterflies Facebook page.  iNaturalist had an interesting sighting of a cabbage white photographed in Dubuque on January 25.  I would assume that was an outlier, and can only speculate on the conditions that would make its emergence possible.
The first butterflies seen each year are usually those that overwinter as adults--mourning cloak and eastern comma are the most common, but gray comma and compton tortoiseshell are also possible.
My photograph of the mourning cloak with her eggs was taken in July.  They deposit up to 250 eggs at a time, usually clustered together around a stem, but also as in my photo under leaves.  Larva grow together in a colony, and they and even the pupae twitch together when disturbed. (Scott, 1986).  People who have raised this butterfly commercially tell me that this butterfly will feign death or "play possum" at times when disturbed.
As the season progresses we will start to see other species.  By late March or early April we will start to see cabbage whites and black swallowtails, which over winter in the chrysalis stage.  Red admirals show up fairly early as well.  The bulk of the Red admirals in Iowa originate from individuals that migrate from locations south of us, but there seems to be evidence that some individuals over winter in Iowa as well, possibly in the chrysalis stage.  Small numbers of red admirals can show up very early, with higher numbers showing up later on.
Henry's elfin
By mid April a number of species will be present, including painted ladies, American ladies, eastern tiger swallowtails, and spring azures.
A special butterfly called Henry's elfin shows up in mid to late April.  This is a small, easily overlooked butterfly that has a short flight time of one to two weeks.  Its caterpillar host plant is redbud, and it seems only to be found where the host plant grows in nature--along river corridors in the southern third of the state.   It is very small and dark, and  you might mistake them for small skippers or even large flies until you get a good look at them.  They can be present in high numbers and you won't notice them unless you are looking for them.
If you look closely at my photo you can see that the butterfly is leaning strongly to its left side.  The wings are held together but are at about a 45 degree angle to the ground.  There is a reason for this.  Butterflies are cold blooded and need to heat up in order to fly.  This individual is doing a behavior called lateral basking.  It is holding its wings perpendicular to the sun so that it can warm up faster.  I took the photo on a cool day--temperatures were in the high 50s to the low 60s but it was sunny.  The basking behavior was very obvious.  As the day warmed up the basking became a little less noticeable. 
I have been doing this butterfly forecast for a number of years now.  I hope I pass along a little bit of information about the butterflies, but I really want to pass along some of the passion I feel for them as well.  And it is not just about the butterflies.  Take a walk in the woods and smell the freshness of the damp leaves and mosses.  Listen to the birds.  Listen for frogs singing.  Look for spring wild flowers--they will be up soon.  Watch for butterflies while you are enjoying nature.
All the best.
                                          Harlan Ratcliff
 
  The Butterflies of North America  A Natural History and Field Guide.  James A. Scott, Stanford University Press, Stanford CA 1986.  
  American copper