|The Poweshiek Skipper Project|
|Butterfly Forecasts for Central Iowa|
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.