|The Poweshiek Skipper Project|
|Butterfly Forecasts for Central Iowa|
|October 2016 to end of year.|
end of the butterfly season is upon us. Soon we will be dealing
with other fun stuff, like snow and freezing rain and cold. But
there is still a little butterfly time left.
Butterflies stick around in good numbers and diversity until the first frost. Then smaller numbers of a few species stick around until the weather conditions no longer allow them to fly.
But we can still have some magnificant, butterfly-filled days. Enjoy them while you can because the seasons are changing.
By the first of October the monarch migration is mostly over. However, the monarch numbers have been fairly high this year and we should still see some for a while. Other migratory butterflies like painted ladies, red admirals, and common buckeyes will be seen, but we do not normally get high populations from the north migrating through Iowa.
Some butterflies, particularly those that have multiple generations each year, can reach high numbers in the fall. We will see high numbers of orange sulfurs and clouded sulfurs, along with cabbage whites. Some of the small grass skippers can be pretty common, particularly tawny-edged skippers, Peck's skippers, fiery skippers, and sachems. Common checkered skippers can also be found late in the season.
There may be a few eastern-tailed blues for a while yet. Occasionally gray hairstreaks can still be seen in October.
Black swallowtails and eastern tiger swallowtails can sometimes persist. One year, I even saw eastern tiger swallowtails on Thanksgiving Day.
There are a few butterflies that spend the winter as adults. We will see these butterflies late in the fall, and they will be among the first we see in the spring. They include eastern commas, gray commas and morning cloaks.
I would rate 2016 as a pretty good year for butterflies--numbers were probably a little above normal. I saw 51 species, mostly in central or southern Iowa, and was able to photograph 46 of them. Probably my favorites were the half-dozen or so Henry's elfins that I saw in mid-April, and the single Reakirt's blue that I saw in July. Cloudless sulfurs and sleepy oranges were a treat at Medora Prairie in early September. While I never got close enough to get a really good photo, I saw regal fritillaries in several locations this year, some of them quite unexpected. Finally, this butterfly season probably had the highest number of silver-spotted skippers of any year I can remember, and silver-spotted skippers are such charming butterflies that they were a special treat.
I attempted to have a couple of butterfly walks this summer but they were cancelled by other committments and weather events. Possibly I will try some next year.
Try to get out yet this year. Sunny days will still bring out butterflies even if the weather is cool. October days in Iowa can be hard to beat.
Butterflies should still be around until mid-October, and maybe even as late as late November, depending on the weather.
Until next year, happy butterflying.
butterfly season is still here and butterfly numbers are still strong,
but the end is near. When you look around one day, you will see
lots of butterflies on the goldenrods, asters, and thistles that are
blooming. If the weather cools down and gets cloudy you might not
see any. Another sunny day and they are back, but in lower
numbers. Some species just fade away but others hang on until the
first frost and even later.
Swallowtails will be seen visiting the tall and bull thistles when they are present in the habitat--those flowers seem irresistible to them. In central Iowa we should see eastern tiger swallowtails, black swallowtails, and giant swallowtails. Some may seem fresh and some will be quite old and battered. Zebra swallowtails have resident colonies in extreme southwest Iowa and extreme southeast Iowa. Pipevine and spicebush swallowtails have both been documented in Iowa, but are quite rare and are usually considered stragglers--there are no known resident populations here of those species.
Orange sulfurs will be present in high numbers, as will clouded sulfurs. The two are difficult to tell apart, especially since the interbreed and produce hybrids. The clouded sulfur is smaller and light yellow above, and the orange sulfur is usually larger and has some orange above. You might see some individual orange sulfurs that are a fairly dark orange-yellow above. Inspect those butterflies closely--they may turn out to be orange sulfurs, but the rarely seen (at least in Iowa) sleepy orange can also be mixed in among them. It is usually as orange as the darkest of the orange sulfurs, but the markings on the underside of the wings are more smudged and lack the spot or spots found on the orange and clouded sulfurs. There have been several sightings of sleepy orange in Iowa this year.
Also watch for cloudless sulfurs. This is a large yellow butterfly, closer in size to a monarch or at least a great spangled fritillary than to the smaller clouded and orange sulfurs. They can also be found on thistles if they are present. Little yellows and dainty sulfurs can be found in high numbers in some habitats, but will be completely missing from others. Cabbage whites can be common, especially in urban environments.
Eastern tailed-blues will still be around in high numbers. Watch for a larger butterfly that somewhat resembles them, the gray hairstreak. They will be found in the same habitats but are large enough that they should be fairly easy to spot.
Pearl crescents should be common throughout the month. Red admirals, painted ladies, and common buckeyes can show up in significant numbers or be totally absent. I have seen a few buckeyes, but the others have been uncommon lately. Viceroys and red-spotted purples should be present in small numbers during the first half of the month.
We have an apple tree, and I almost always can find eastern commas, question marks, northern pearly-eyes, and a number of other brushfoot butterflies feeding on the rotting juices of the fallen apples, and often even on apples still in the trees.
Of course, monarchs put on their spectacular shows in about the middle of September. In good years you may find dozens hanging upside down in a particular tree. Watch them closely--with the wings shut they blend in and look like just another dead leaf. When another monarch approaches, the resting monarchs might open their wings, and give a flash of orange.
Some skippers are slowly fading away but still might be present--least skipper, Delaware skipper, Peck's skipper, and tawny-edged skipper might still be found. I have yet to see Leonard's skipper, but I understand it can be found in the loess hills, especially on blazing stars (Liatris) at the end of August through the first part of September. You have to go to a good prairie to find it, then you will probably need a great deal of luck--they might be found in only a few square feet within several acres of prairie.
Common checkered skippers, Sachems, and fiery skippers all seem to increase numbers at the end of the season.
Don't let too much time slip by. Get outside and watch the butterflies.
the summer rushes by the butterflies continue to thrive. Numbers
increase, especially for those which have more than one generation per
year. We can see rare and not-so-rare migrants from the south as
those butterflies expand their populations.
Red admirals, painted ladies, American ladies, and common buckeyes migrate into Iowa early in the spring and can become quite common. Later in the year, particularly in August, we see little yellows and dainty sulfurs sometimes reach high numbers.
One butterfly that is especially a treat to see is the cloudless sulfur. It is large--maybe twice the size of the orange sulfurs that we see so often. While cloudless sulfurs can be quite common in areas to the south of us, I usually only see them here about once in every two or three years. But they always leave an impression.
This year has been pretty good for butterflies. It seems to me that the numbers are slightly above average. Silver-spotted skippers have been especially abundant recently.
The butterfly walk that I had planned for early July got rained out, but I was able to have a pleasant conversation with a fellow butterfly enthusiast on that day. I had hoped to introduce a few people who might not have seen it to the regal fritillary but it was not to be. I have been fortunate enough to have seen regals on several locations this year. Regals and great spangled fritillaries should still be around for a few more weeks, but they are getting old and ragged.
As always, the most common butterfly this month will be the orange sulfur. Clouded sulfurs are in the mix as well. Eastern tailed-blues, which are normally very common can still be found, but their numbers seem a little lower than normal this year.
Eastern tiger swallowtails can be seen visiting flower gardens and will visit tall and bull thistles later in the month, when they start to bloom. Black swallowtails are around in pretty good numbers now, visiting wild bergamot and hoary vervain. Giant swallowtails should be present and can be quite common and spectacular in some areas. I have seen high numbers of them in Fraser, Iowa near the Boone and Scenic Valley Railroad hub, and also in West Oak Forest in Mills County. I have yet to visit one of the areas that zebra swallowtails can be found, in Shimek State Forest in the south-eastern part of the state, or in Waubonsie State Park in south-western Iowa.
Summer azures will continue to be common throughout the month, with some appearing fresh and others being quite ragged. It is probably too late to see most of the hairstreaks with the exception of gray hairstreak which could be present in small numbers among prairie flowers. Bronze copper can still be seen in August, although I have not seen any this year.
Several of the brushfoot butterflies will be quite common in August, including pearl crescent and silvery and gorgone checkerspots. Hackberry emperor is found in good numbers in wooded areas, and they will aggressively investigate anyone walking by, often landing on them. Tawny emperors have a similar appearance but are less common here than other places.
Viceroys and red-spotted admirals (a.k.a., red-spotted purples) are often seen and are especially attracted to flowing sap or rotting fruit.
Watch for the American snout to show up in small numbers. These butterflies can form huge swarms in Texas and other areas in the south, but we usually only see a few at a time here.
Question mark and eastern comma butterflies can be seen--at our place they are often on our gravel driveway, especially after a rain.
Monarchs will start showing up in greater numbers toward the end of the month.
Least skippers, tawny-edged skippers, and Peck's skippers should be seen all throughout the month. Fiery skippers and Sachems will start showing up late in the month and can be showy on small flowers.
August always seems to come along with lots of other activities--school, sports, fairs, etc. While some of those activities are outdoors, they are often in highly modified areas where the butterflies that happen by are coming from some other habitat. It is worth your time to get to those good habitats to observe and photograph the butterflies. It refreshes my soul to do that.
Go to a prairie or a wetland or a woodland trail. Walk along the edge of a creek or a river. Your troubles will seem a little less immediate. And you will see lots of butterflies.
Until next time:
is a great time to watch butterflies in Iowa. Numbers are high,
and some species that have only one generation are most likely to be
found in July.
But maybe it starts with the flowers. During this month, several species of milkweed are in full bloom. All are attractive to butterflies, but butterfly milkweed, most often found on good prairies, is probably the best.
Large butterflies like great spangled fritillaries and regal fritillaries land, drink a little nectar, then fly off. Pearl crescents use the flowers as a platform for their pre-mating rituals--the female slowly walks across the flower with wings spread, and from one to three males follow, shaking their wings while they try to impress her. Many different types of butterflies visit, but hairstreaks stay on the flowers for long periods of time. If you want to find the hairstreaks that come out in July, look first on butterfly milkweed, then on common milkweed.
Banded and coral hairstreaks are probably the easiest to find, but also look for Edward's, hickory, and striped hairstreaks especially in areas with savanna. Acadian hairstreak may be found in wet prairie areas, especially in the northern part of the state. Juniper hairstreaks have a second generation that comes out in July, but is more common in the western part of the state than the central part. Gray hairstreak may show up in July, and unlike the other species will still be found at the end of the summer.
Gray coppers have one generation in Iowa, with peak populations in July. They can be quite common in certain habitats--generally prairies, and they can be completely absent from others. Bronze coppers can often be found in weedy wetlands, although I have not seen them this year or last.
I have seen little glassywing in fairly large numbers this year, and they should persist until early July. Dun skippers have also been present. We should see least, Delaware, common checkered skippers, and crossline skippers in some numbers before the month is over.
I mentioned in my last post that I was planning a butterfly walk for Rolling Thunder and Medora Prairies on July second. More details can be found here. Byssus, two-spotted, and arogos skippers have all been documented on one or both of the sites. I have taken photographs of the first two, although I have not seen either of them for more than ten years. We should see some other good butterflies, though. I photographed a sleepy orange on the access road to Medora Prairie about two weeks ago--with luck we might see it again.
Prairies will have large numbers of common wood-nymph. In my opinion, the wood-nymphs that are found in some of the central Iowa prairies are a deeper black than those that might show up in a more wooded area. I think the populations might be genetically different. Wood-nymphs have a tendency to be found in tall grass areas, and when startled will fly a short distance and hide back in the weeds. Little wood-satyrs and northern pearly-eyes have similar habits and can be frustratingly difficult to photograph.
As always, orange sulfurs and clouded sulfurs will be the most common butterflies. Little yellows should start to show up in July, increasing in numbers until near the end of the summer. Cabbage whites are usually present, but sometimes the white morph of orange sulfurs can be more common. Checkered whites and cloudless sulfurs are possible, and stand out by being somewhat larger than other white or yellow butterflies. Both are usually rare in Iowa.
Monarchs should be seen but will be more common later in the summer. Look for viceroys and red-spotted purples throughout July. Red admirals, eastern commas, and question mark butterflies will be common yard butterflies. If you have a fruit tree, look for them in the tree on any fruit that is over-ripe. They can even be found in mulberry trees. They also can often be found on gravel roads where there is a little bit of moisture.
Black swallowtails, eastern tiger swallowtails, and giant swallowtails can all be found throughout the entire month of July.
So get out and enjoy the butterflies.
numbers and diversity start picking up in June. By the end of June
the butterfly populations will be between ten and a hundred times what
they averaged in May.
Question mark butterflies can be seen often in June, basking with the wings spread and exposing their bright orange and black uppersides. Question marks are larger than the similar eastern comma, and usually have a longer tail (although that characteristic is highly variable). They have two distinct morphs, a uniformly brown winter morph and the more mottled summer morph that is shown here. They may overwinter as adults, but they have also been documented to migrate in some places.
Other brushfoot butterflies that will be seen and sometimes will be quite common include eastern and gray commas, American ladies, and painted ladies. Red-spotted admirals (also known as red-spotted purples) will be seen near wooded areas as will viceroys as well.
We might see a few monarchs at the beginning of the month, followed by a dry spell. By the last week of the month we should be seeing them again in higher quantities.
By the middle of the month numbers should really be picking up, and we might see the first great spangled fritillaries, hackberry emperors, northern pearly-eyes, and little wood satyrs. Common wood nymphs will become quite common--in some dry prairies they will be the most common butterfly seen in the middle of the day.
Of course, pearl crescents will be quite common. Silvery checkerspots can be common, especially in wooded areas. Prairie areas may have gorgone checkerspots mixed in with the other two.
Black swallowtails, eastern tiger swallowtails, and giant swallowtails should be possible throughout the month. They might not be common, but are large and easily seen when present.
The orange sulfur will likely be the most common butterfly throughout Iowa for the entire month, and for the rest of the summer. Clouded sulfurs and cabbage whites will be common as well. The first little yellows may show up by the end of the month, as well as dainty sulfurs in specific habitats.
Among the gossamer-winged butterflies two blues will be very common. First, the summer azure will have a population peak starting in the first or second week of June. They will be present until late in the summer. Eastern tailed-blues have already been seen, but they will become quite common by the latter part of the month. Bronze coppers and gray coppers will be found toward the end of the month, but usually only in certain habitats--usually wetland areas or good prairies.
By the end of the month several hairstreaks will make appearances. Coral, banded, and Edward's hairstreaks can often be found on milkweed flowers in areas that have trees of their host species--cherrys, oaks, hickories, wild plum, and others. They can also sometimes be seen chasing each other near the host tree.
Acadian hairstreak uses willow as a host plant, and is rare but can sometime be seen in wetland areas. Juniper hairstreak has a second generation which starts at the end of June and the first part of July. While the host plant, eastern red cedar, is found all over Iowa, sightings are more likely to occur along the western or eastern borders of Iowa for some reason.
Harvesters can be found all summer, having multiple overlapping broods. However, they are always rare.
Many species of skipper show up during June. We should see the large, fat, silver-spotted skipper along with a number of smaller spreadwings. Common checkered skipper and common sooty-wing can usually be seen. Horace's dusky wing and Juvenal's duskywing may both be present--I have to admit that I find them frustratingly difficult to tell apart. Peck's skipper is small and quite distinctive and usually common enough to be readily seen. Least skipper is small and light brown with a bright white belly. Once you have recognized it, this skipper is easily distinguished from the other skippers found in Iowa.
I plan on having a butterfly field trip on Saturday, July 2. We will go to Rolling Thunder and Medora Prairies. It will start at about 9:30 am at Rolling Thunder, and we will proceed from there at about 10:30 to Medora Prairie. I will put more details out on the Iowa Insect and the Iowa Native Plants listserves. If you are not on either list, you can email me (harlan(dot)ratcliff(at)gmail(dot)com) and I will send you the specifics.
It is likely to be hot, so bring water. Prairies also have plants that poke or scratch, and poison ivy, so the smart people will wear long pants or long-sleeved shirts. (I will probably wear shorts--I am kind of used to this stuff). There will be biting insects and ticks.
If we are lucky, we should be able to see regal fritillaries. There are also good populations of gray coppers, common wood nymphs, great spangled fritillaries, and coral hairstreaks.
Several rare skippers have been found in these two prairies, but in my experience they can be quite rare so if we see any of them we should consider ourselves lucky.
The visit will be non-consumptive: Emphasis will be on observing butterflies and not on catching them.
So mark the date. I hope to see you then.
brings summer weather.
Hopefully we will see some of that when the rains stop in a few days.
We will see the flowers of May along with its butterflies.
The diversity of the butterflies on the wing increases throughout the month, although sometimes the numbers can be a little disappointing. If you were to graph the populations over time for Iowa's butterfly species, you would find most of them have what statisticians call a "normal" distribution. Those with one generation have one peak. Some species have three peaks. The month of May usually falls within the distribution curves for many species, but the peaks are usually earlier or later.
Cabbage whites are fairly common and can be among the first butterflies to emerge in late March or early April. They don't all emerge at the same time, and they reach a population peak in mid to late April, depending on the weather. Adults live for about three weeks. You might see the adults remaining from the first generation in early May, and you might see some from the second generation in late May, but the peak populations fall outside of the month.
Henry's elfin and Olympia marbles are both rarely seen in Iowa, with the Olympia marbles possibly extirpated or nearly so. Both have population peaks in April but they can also be found in May. Look for Henry's elfin near redbud trees in the southern part of the state.
Clouded sulfurs have been fairly common and will continue to be. In my experience, orange sulfurs and clouded sulfurs are often similar enough in appearance that they are difficult to distinguish, but the ones that are clearly a little larger and have more orange (orange sulfurs) are usually more common when the weather gets warm, while the smaller, more yellowish clouded sulfurs are most common in early spring and late autumn.
Black swallowtails and eastern tiger swallowtails should be seen throughout May, and giant swallowtails will come out in the later half of the month. Those three can be found all over the state. Although they are sometimes uncommon they are large and easily seen. Zebra swallowtails should be out as well, but they are only reliably found in the extreme southwest corner of the state. While spicebush and pipevine swallowtails can occasionally be found in Iowa, they are rare and do not have resident populations in the state.
Red admirals are quite common right now and should continue to be for a while. You may see American ladies and painted ladies as well. Eastern commas may still be seen, but the slightly larger question mark butterfly is more likely to be seen in May. Toward the end of the month we should start seeing red-spotted admirals (formerly called red-spotted purples) and viceroys. First sightings of monarchs will probably happen in May, but they will still be uncommon.
Small numbers of eastern tailed-blues may be fund in the first part of the month, followed by larger numbers of summer azures sometime later.
Silver-spotted skippers, hobomok skipper, Peck's skipper, and common sooty-wing skipper are all possible in the last half of the month. Their numbers vary from year to year--sometime they can be quite common, and sometime they can be difficult to find. Watch flowers for their nectar-seeking visits.
Get outside and enjoy the butterflies.
seasons seem advanced by a week or two this year due to warm weather.
For the first time since I have been tracking butterflies we had some
butterflies observed in February in Iowa. Sibylla Brown saw a
comma on February 20 in Decatur County, Bill Witt saw a mourning cloak
in Cedar Falls on February 27, and Mark Brown saw a cabbage white in
Dubuque on February 28. Jim Durbin's database at
insectsofiowa.org has a single record
for a mourning cloak on February 24, 1998, but the others are probably
new early records.
Chasing butterflies in April is fun. It is fun because it is finally time to get relief from the long winter. The air always seems cleaner and fresher in April. Many of the butterflies you find will be first of the year for those species. And there are a couple that can only be found in April or perhaps early May in Iowa.
The large brushfoot butterflies that spend the winters as adults may still be around--eastern and gray commas and mourning cloaks are the most common in this area. Compton and Milbert's tortoiseshells fall into that group as well but are not nearly so common.
Cabbage whites are always early emergering butterflies, as are black swallowtails and azures. There seems to be a lot of discussion about whether the azures we see in April are spring azures, Celastrina ladon, or a spring-emerging brood of summer azure, C. neglecta. I think it is safe to say that the issue is pretty complicated, and the experts do not all agree. One discussion of the forms found along the east coast can be found here, and argues that most individuals found early are summer azures. Spring azures are present but rare. Jeffrey Glassberg suggests that all found in the spring are one species, and those later in the year are a different species. In addition, there are a number of species described based on hostplant preferences and other things. Bugguide also has some discussion of the various forms.
Olympia marbles have been found in Iowa in the past. There is some thought that they have been extirpated from most of the sites they have been found in the past, but there have been a couple of recent sightings of individuals. This butterfly is known to be difficult to locate, and may be overlooked. Late April through early May is the time to look for them here.
Henry's elfin is another butterfly that can only be located in the same small April/May time window. They can be found on and around redbuds. One of the best places to look seems to be the parks on and around Lake Red Rock. There have been sightings in Cordova Park on the north side of the reservoir and from Elk Rock State Park on the south side. Look in and around redbud trees and on nearby flowers. I have really only seen them once, and I did that by sitting on a chair near a redbud tree, and looking up into the tree. After about twenty minutes I saw an individual, and I saw another one later.
I used the same technique a few days later at the Ledges State Park, and watched redbud trees for an entire morning. I didn't see any then. Either they are not found there, or maybe they weren't out that day, or my method doesn't work well and I just got lucky once.
Hairstreaks that have trees as host plants often perch on the tree, then fly out in short little flights, chasing individuals of the same species. Juniper hairstreaks, which will have a flight in late April and early May have a similar behavior. I have been lucky enough to see juniper hairstreaks on my own property in central Iowa, but they are probably more reliably located in western Iowa in the Loess hills.
The Vanessa species--red admiral, painted lady, and American lady, may show up in some numbers in mid to late April. Royce Bitzer already documented a couple of painted ladies in Ames in early March. Red admirals are often quite common and showy early butterflies, and are often present in high numbers early.
By the end of April we should see eastern tiger swallowtails, eastern tailed-blues, and clouded or orange sulfurs. Pearl crescents should be chasing each other around the taller flowers.
I mentioned in the last post that I would try to organize some butterfly excursions this year. I want to try one on Saturday, April 23, and another one in late June or early July. I am not sure right now what the interest level will be, or how many people if any will want to be involved. I will experiment a little with some different formats to see if there is interest and what people want to do. I plan to do the second on in sort of a field trip format, trying to get a group that sort of stays together. I am planning it for central Iowa, with regal fritillaries as the primary target, and possibly some rare skippers as a secondary target.
The first trip will be a little bit more like a scavenger hunt, and will be in southwest Iowa. I would encourage people to meet up initially, then disperse over a wider area and look for some rare butterflies. Fulsom Point Preserve and West Oak Forest will be the initial locations (we will likely run across mushroom hunters). Other locations may be visited, depending on individual preference and tolerance for physical activity and/or driving. I would expect to leave the Des Moines area by 8:00 am and return by late afternoon. Contact me by email if you are interested in participating: (harlan(dot)ratcliff(at)gmail(dot)com). Include a phone number where you can be reached if there is a need to cancel or postpone.
I will send details out by email and also post them to the Iowa Insects listserve.
|March 1-31, 2016|
you feel the days getting longer? Warmer weather is just around
the corner, and with it come the butterflies. We might see some by
the end of the week.
In most years, the first butterflies of the season show up in March. There are really only a handful of species that are normally seen this early. Mourning cloak, eastern comma, gray comma, Milbert's tortoiseshell and Compton tortoiseshell all over-winter as adults and are the first butterflies seen in Iowa. Of those, mourning cloak and eastern comma are by far the most common in central Iowa, the others being more likely to be seen in wooded areas in the north eastern part of the state.
Watch for wet spots on tree trunks--telltale evidence of leaking sap. These butterflies in particular are attracted to sap and can often be found in abundance anywhere it is found.
In some years only a few individuals will be seen late in the month. If the weather is consistently warm for long enough we might see cabbage whites, clouded sulfurs, or red admirals by the end of the month. Cold years we have to wait until April to see them.
The low numbers and lack of diversity we see in this month are compensated by the joy that we feel just to see a first of the year butterfly, and we know the season will gradually get better. It is always good to get out into a woodland early in the year to look for the earliest flowers and hope to see a butterfly. Some woodlands have spectular shows of spring ephemeral flowers, but before they show up you might notice the green lush displays of mosses and liverworts, and the exotic colors of lichens. The smells of the slowly warming woodlands are terrific also, and alone are worth the trip.
This is my ninth year of posting a butterfly forecast, and I have enjoyed doing it. I am going to change things up a little bit this year, however. I plan on posting once per month this year, rather than twice as I have done in the past. I also plan on having two or three butterfly excursions this year within Iowa. These will be very informal, and open to the public. It will include visits to habitats within a particular geographic area of the state, and I will come up with some plans for looking for particular species. Depending on the number of people who show an interest and where they are from we can car pool, and we might go as a group or disperse into smaller numbers.
Watch for more details in the April forecast.
If you are looking for a nice social activity related to insects, check out the Day of Insects at Reiman Gardens. It is coming up in early April, so sign up soon.
There are a few web sites that can give clues about what butterflies are flying. The North American Butterfly Association recent sightings page lists butterflies seen all over the country. Right now they are showing sightings mostly from the southern states, but as the butterflies show up in the more northern states they will be reported there as well. Unfortunately, Iowa is not represented as much as I would like to see. Wisconsin butterflies lists recent sightings, although we usually see them here before they do up there. (As I was writing this, I checked the site and see that there have been two eastern comma sightings already this year in Wisconsin). Butterflies and Moths of North America has a recently verified sighting page--some are recently recorded, and some are just recently seen. You can even find hints about recent sightings on bugguide.
Of course, if you are looking for a specific butterfly you can get a pretty good idea when it shows up in Iowa by checking out the Insects of Iowa web site for that species.
So get out and look for butterflies. They have already beaten us in Wisconsin.