April 03, 2024

Red Admirals Arrive Early in Central Iowa

I spotted the first Red Admirals of the season in Ames, Iowa on March 30 – the earliest arrival date since 2012. On this sunny early afternoon, I was walking along a path in the woods behind our house, on the way to check two wildlife cameras, when I spotted the first of them basking on a bed of leaves. After watching and photographing it for some minutes, I continued along the path and then uphill toward the fox den that we were monitoring. While I was changing the batteries in the cameras, there was a dark brown flash – another Red Admiral, several times landing and flying short hops before disappearing to the northeast.

Upon returning to the initial spot, there was yet another Red Admiral with more wing wear than the first one. This butterfly seemed to be perching and patrolling the area. Finally, I saw a fourth Red Admiral in migratory straight-line flight toward the northeast.

These butterflies arrived shortly after a tongue of warm, moist air flowed toward us from the south. This raises the question of whether Red Admirals had been moving gradually northward during the past several weeks, or whether instead they had come abruptly northward for a long distance within just a few days. A series of first-of-season sightings along the migratory route therefore would be interesting.

Have Red Admirals actually been arriving here earlier in more recent years? Statistically, no – not yet anyway. First arrival times here typically vary widely from early April to mid-May with no definite trend in either direction. Even so, our unusually warm winter had me wondering if they might arrive early this year. Stinging nettles have also been sprouting earlier this year, so the new arrivals should not lack for larval food plants.

Whether or not they are arriving earlier, another possibility is that they might be overwintering farther north in recent years in response to the warming climate.

Posted on April 03, 2024 04:09 AM by iowabiologist iowabiologist | 0 comments | Leave a comment

August 23, 2023

Lepidoptera of Ukraine

Today, August 23, is Ukrainian National Flag Day, and tomorrow, August 24, is Ukrainian Independence Day, marking 32 years for Ukraine as an independent country.

As my way of celebrating these Ukrainian national holidays, I encourage you to visit the iNaturalist project page, Lepidoptera of Ukraine, at https://www.inaturalist.org/projects/lepidoptera-of-ukraine . Ukraine is quite the biodiverse country, from the montane conifer forest of the far western Carpathians to the central European mixed forest of the northwest, the forest steppe of the northeast, the open southern grassland steppes, and along the southern coast of Crimea, the Submediterranean Forest Complex. This great diversity likely yields correspondingly diverse communities of butterflies and moths.

Last but not least, I've been amazed by how many Ukrainians have been posting observations on iNaturalist, despite the ongoing events of this terrible war.

Posted on August 23, 2023 10:30 PM by iowabiologist iowabiologist | 0 comments | Leave a comment

April 10, 2023

Red Admirals Are Arriving in the Upper Midwest

Spring has arrived here in Iowa, and so have the butterflies, including Red Admirals. After the last three years with low numbers, it’s now looking like 2023 is going to be a more active, abundant, and exciting year for Red Admirals. I’m still not sure how the Painted Lady population will develop this year, owing to the unusually intense and variable weather in California this past winter.

Red Admirals are now arriving in the upper Midwest, following two strong and very stormy weather systems that transported warm, moist air from the Gulf of Mexico into our area. Red Admirals arrived soon afterward, with the first report from Omaha, Nebraska on April 4. I spotted my first ones here in Ames, Iowa on April 7. It’s likely they were here sooner, perhaps as early as March 31, but it was difficult to tell because cold weather followed each of the two frontal passages. Since then, I’ve started receiving more reports from around the upper Midwest.

As always, I’m seeking not only first sightings of Vanessa species, but also sightings of migrating butterflies and sightings throughout the season.

Posted on April 10, 2023 05:38 PM by iowabiologist iowabiologist | 2 comments | Leave a comment

September 26, 2022

Autumn Painted Lady Migration in Central Iowa

A southward Painted Lady migration has been underway in central Iowa for at least the past three days. After a summer with none observed here, a few appeared in late August into mid-September, and then recently, larger numbers arrived after September 21. Although most have been spotted nectaring, several have been seen flying southward after the passage of a cool front on September 24. As of today, September 26, winds continue blowing from northerly directions, carrying Painted Ladies southward at heights of from 5 to 10 meters/15 to 30 feet.

Posted on September 26, 2022 07:30 PM by iowabiologist iowabiologist | 1 comment | Leave a comment

August 18, 2022

First Painted Lady of 2022 in Ames, Iowa

On August 16, 2022, I spotted the first Painted Lady of the season here in Ames, Iowa. It was large and fresh, with damage to the right hind wing that might have been caused by a bird attempting to catch it. The butterfly was nectaring on ironweed in a planted prairie bioswale. It spent at least 20 minutes in this area visiting ironweed flowers. https://www.inaturalist.org/observations/131257109

During a La Niña year such as this one, when the spring generation of Painted Ladies in the American Southwest is generally very low, Painted Ladies typically arrive in Iowa no earlier than mid-August. This one arrived at a time when I was expecting the first one to appear soon during the upcoming days.

Posted on August 18, 2022 03:31 PM by iowabiologist iowabiologist | 0 comments | Leave a comment

April 27, 2021

Red Admirals Arriving in the Upper Midwest

I've received an e-mail from a friend who was wondering when Red Admirals would be arriving in the upper Midwest this spring. He had not seen any postings of that species on the Wisconsin Butterflies recent sightings page, or on iNaturalist, and asked me how unusual it is to not see Red Admirals this far into the season.

The first Red Admirals in central Iowa have been later than average this year (the average arrival time here is in mid-April, but the first one can arrive as early as late March to as late as mid-May). There have been several possible reasons for this:

1) It has been a generally cold spring until now.
2) Whenever there were warmer temperatures above 60 F with southerly winds, the air was very dry. They prefer not only warmth and winds from the south, but also sufficient humidity, with dew points above 55 F.
3) The jet stream for the last few weeks was passing from central Texas through Mississippi, Alabama, and Georgia and then into South Carolina. This pattern kept the warm, humid Gulf air well to our south, and brought several weeks of rainy, stormy weather to those states while we in the upper Midwest stayed unusually dry.

All three of these factors changed yesterday, April 26. A loop in the jet stream moved northward, which allowed southerly surface winds to bring warm, moist air into our area. Not only did the temperature rise rapidly into the low 80s, but the dew point also gradually rose from 41 F before sunrise to 56 F in mid-afternoon. So yesterday was the first day this year that was favorable for Red Admirals in our area to be active and to migrate.

This spring I've been out checking the Iowa State University campus for Red Admirals each sunny or partly sunny afternoon above 60 F since late March, without finding any. Likewise, there were none on April 25 - it was still too cool and dry. But when I went there yesterday, I found the first one of the season, perching on and patrolling around the sunny west wall of Catt Hall (https://www.inaturalist.org/observations/75450713). It was a pleasant surprise, but one also anticipated due to the favorable conditions. Now, as spring continues and the weather becomes more favorable, we can expect more Red Admirals to be arriving in the upper Midwest.

For additional details and a dew point temperature map for April 26, see https://vanessa.ent.iastate.edu/red-admirals-arriving-upper-midwest .

Posted on April 27, 2021 08:45 PM by iowabiologist iowabiologist | 0 comments | Leave a comment

January 28, 2021

Atmospheric River Impacting California

This event has the potential to trigger a bloom of desert annuals in the southwestern United States, perhaps followed by an outbreak of Painted Ladies by early March. This depends on whether enough of the heavy rainfall predicted for the coastal regions of southern California on Friday, January 29 crosses the San Jacinto Mountains to substantially water the deserts to the east.

From the U.S. National Weather Service on January 28:

An ongoing heavy precipitation event continues to unfold across central and southern California this afternoon as an atmospheric river swings through the region. Up to 12 inches of rain has already fallen along coastal areas, with more than 4 feet of snow across the central Sierra Nevada. The focus for heavy rain going into tonight will shift to coastal sections of southern California. Up to 3 inches of rain is expected to fall here, with locally higher amounts. Flash flooding and debris flows will be possible near recent burn scars, as soil cannot retain much rain in a short amount of time. Flash Flood Watches are currently in effect. Meanwhile, heavy snow is expected to continue through Friday morning across the central and southern Sierra Nevada. A widespread additional 1 to 3 feet of snow can be expected, making travel extremely dangerous and impossible at times.

If not for this atmospheric river, 2021 would probably not have been a potential year for an extensive Painted Lady outbreak. The Pacific Southern Oscillation is currently in a strong La Niña phase, which brings sinking air and dry conditions to the southwestern deserts:

La Niña—the cool phase of the El Niño-Southern Oscillation climate pattern—was firmly in place across the tropical Pacific in December 2020. Forecasters estimate a 95% chance La Niña will last through Northern Hemisphere winter. La Niña can influence seasonal climate in the United States. Conditions so far have not looked especially La Niña-like, but winter is far from over.


The atmospheric river itself is impressive - appearing on satellite photos as a curving loop of clouds extending from east of Hawaii across the Pacific into central California, then continuing northeastward into eastern Washington, southeastern British Columbia, and southern Alberta. The leading edge of the loop is forecast to move eastward over the next 24 to 48 hours, which will bring the potential for rainfall to southern California and Arizona. The loop itself is propelled by circulation around a strong low-pressure system that has been spinning to the west of the Oregon/Washington coast for the past three days.

Events such as this one suggest the potential for Painted Lady outbreaks to be triggered even during years which would otherwise not be favorable for them to occur. Will there actually be a large outbreak this year? Observers in California and the Southwest, please keep watching for Painted Ladies, and let us know what you see!

Posted on January 28, 2021 10:44 PM by iowabiologist iowabiologist | 1 comment | Leave a comment

July 24, 2020

Painted Lady Outbreak in Nebraska

Fresh Painted Ladies have been proliferating in Nebraska since about July 18, suggesting a recent mass emergence. This outbreak has been most closely monitored in the eastern part of the state, but large numbers have been observed throughout Nebraska. Meanwhile, here in central Iowa, 150 miles/240 km to the east, only a few have occasionally been spotted in the past several weeks. Will they eventually arrive here, and if so, when? I keep watching the skies for migrants and the flowers for many sudden arrivals, but so far, I've seen almost none.

Almost none, because this afternoon, July 23, I spotted a single Painted Lady, the first I had seen in just over three weeks. It was nectaring - or trying to nectar - in our small prairie patch on the Iowa State University campus, but wasn't having much luck because a particularly aggressive and persistent Monarch chased it several times and drove it away. So I have an observation, but no photo to accompany it.

Shortly after seeing the butterfly, I realized that the weather was turning warmer and more humid, and the wind was increasing from the south. Could this type of weather change suggest that Painted Ladies might arrive soon, riding the wind from some source region somewhere to the south? Or will Painted Ladies arrive here simply by expanding eastward from what may be a source region in Nebraska?

Because migrating butterflies often take advantage of winds blowing toward the direction to which they are inclined to go, wind flow patterns often reveal the course of a migration. The mid-day wind flow patterns from EarthWindMap on July 17 and 18th showed widespread southerly wind flow across western Iowa and eastern Nebraska on the 17th, and across eastern Nebraska through all of Iowa on the 18th. If the Painted Ladies had come from a widespread area somewhere to the south or south-southwest, one would have expected a strong front of arrivals in both states at about the same time. The current pattern of abundance suggests possibly a more localized irruption or a wind-borne migration from a relatively small source region. Observing flight and wind directions, looking at relative butterfly abundance in different locations over time, and examining patterns of daytime ground clutter on radar maps may provide helpful information about how this irruption develops and spreads.

Posted on July 24, 2020 06:42 AM by iowabiologist iowabiologist | 1 comment | Leave a comment

October 08, 2019

Autumn Red Admiral Migration in Central Iowa

Although Red Admirals were first seen migrating southward in central Iowa in early September, their migration remained sporadic and sparse here until the end of the month. This year, unlike during 2017, most of the migrating Vanessa have been staying to the north, in Minnesota, Wisconsin, and Michigan, for much of September. That is, until the weather patterns changed during the past week....

Larger numbers of Red Admirals first appeared in Ames on September 30, when an unseasonably warm and humid air mass over the Midwest led to the development of gusty south winds that kept the butterflies, along with some roosting Monarchs, from proceeding further southward. Some of these butterflies, seen feeding on fallen apples in an orchard, were an intermixture of fresh and partly-worn individuals, perhaps from two different generations.

A cold front moving eastward into this warm, humid air mass spawned strong to severe thunderstorms during the afternoon and evening of October 1, which was followed by cool overcast for the next two days. October 4 then dawned mostly sunny, a cool, crisp day with light to moderate winds alternating between northeasterly and southeasterly. And that's when the migrants appeared again - a nearly equal mixture of Red Admirals and Painted Ladies, along with three Monarchs, flying generally south-southwest from 1 to 3 p.m. through cool air that never got warmer than 60 F.

October 5 was another thundery day of heavy rain, followed by a cool sunny day on the 6th, when the Vanessa butterflies were once again out and about and showing signs of moving. Then the migration really picked up on the 7th. As the air warmed above 60 F after 10 a.m., the butterflies started moving, and by 12 p.m., the southward migration was definitely underway. Being mostly Red Admirals this time, the migrants arrived on average once every four minutes across a 100-foot east-west line, with sometimes two or three coming in a minute around the 1 p.m. peak. The migration then gradually decreased and ended for the day shortly after 3 p.m. At that point, I went back to the orchard that I had visited on September 30 and found about 30 Red Admirals there along with a few Polygonia comma, all feeding on fallen apples (https://www.inaturalist.org/observations/34054397). They remained active there until after 4:45 p.m., when the area was becoming shaded and the butterflies started departing for the evening.

Although migrating Vanessa butterflies are not as obvious as Monarchs, when they are as abundant as they have been here recently, they are readily spotted flying generally southward. Go out to an open area on clear, crisp days with nearly-calm to moderate northerly or westerly winds and watch for dark or orange butterflies smaller than Monarchs flying from near the ground to eye level to 30 feet/10 meters overhead. Even if you do not see any flying, look at the fallen fruit beneath fruit trees for Red Admirals and other butterflies taking advantage of the feast.

Posted on October 08, 2019 04:20 PM by iowabiologist iowabiologist | 1 comment | Leave a comment

July 31, 2019

Another Painted Lady Irruption in the Upper Midwest

One month after the last Painted Lady irruption in the final days of June, another generation, perhaps even larger, suddenly emerged in central Iowa on July 29 and 30. I went out on a survey and collecting trip in Story and Boone Counties on the 30th, and found hundreds of fresh butterflies milling around and flying across Highway 17 and other local roads between Boone and Luther. There was also a large emergence between Polk City and Ankeny, with perhaps 200 along a stretch of highway between these towns. Hundreds were also observed along Interstate 80 in eastern Polk, Jasper, and Poweshiek Counties, but there were very few along I-80 farther east in Iowa and Johnson Counties, suggesting a somewhat localized irruption so far. Many of the butterflies seen along I-80 were flying north, but others were flying in various different directions.

Farmers in our area continue to have problems with "thistle caterpillars" feeding on their soybeans. While I was out monitoring yesterday, I met one grower who said that he had had to spend $30,000 this year for spraying his soybean fields for Painted Lady caterpillars. He was also disappointed to hear from me that there could be yet another generation of larvae before a final brood of butterflies emerges in early September to fly south.

This irruption began earlier in the month in the Omaha, Nebraska area, sometime between July 18 and July 23, as reported by @langabee from weekly surveys there. From those reports, I was anticipating another irruption in central Iowa, while wondering why it wasn't happening here for another week to 10 days after beginning in eastern Nebraska. Perhaps some observers in western Iowa can fill in the blanks here.

Posted on July 31, 2019 08:01 PM by iowabiologist iowabiologist | 2 comments | Leave a comment