Red Admiral Butterfly

Red Admiral Butterfly

American Lady Butterfly

American Lady Butterfly

Painted Lady Butterfly

Painted Lady Butterfly

West Cost Lady Butterfly

West Coast Lady Butterfly

This is a web site to coordinate observations of territorial behavior, migration, life history, population studies, seasonal variations in abundance and body size, and number of broods per year (voltinism) of butterflies in the genus Vanessa, including Vanessa atalanta, V. cardui, V. virginiensis, V. annabella, V. tameamea, and V. kershawi. (Red Admiral, Painted Lady, American Lady, West Coast Lady, Kamehameha Butterfly, and Australian Painted Lady).

Although the lady butterflies of the genus Vanessa are not as familiar or as well-studied as the Monarch (Danaus plexippus), their behavior and migration are likewise well worth observing. Much remains to be discovered about their habits and how their behavior and seasonal distribution varies by geographic location. Observers and experimenters ranging from casual to serious can discover new and valuable information about these butterflies. The list above links to more detailed information, including summaries of published findings and methods for observing these fascinating butterflies.


Royce J. Bitzer, Ph.D., Department of Entomology, Room 539 Science II, 2310 Pammel Drive, Iowa State University, Ames, Iowa 50011, U.S.A.
Phone: (515) 451-9057   e-mail: mariposa@iastate.edu

This site was most recently updated on April 27, 2021.

Recent News

April 27, 2021

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.  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.

Here is a dew-point map for 1 p.m. Central Daylight Time, April 26, showing the warm, moist, southerly air flow into the upper Midwest (attribution: RAL Real-Time Weather Data, National Center for Atmospheric Research, weather.rap.ucar.edu/surface):

Also note the dry line running from southwest Texas to western Kansas.  Here the moist air from the Gulf of Mexico meets dry air from the desert southwestern states.  Thus this line is likely to be the farthest possible western extent of any ongoing Red Admiral migration at this time.  The dry line is also notorious for spawning severe thunderstorms and tornadoes along the moist side of the line.

-- Royce Bitzer

January 28, 2021

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.

https://www.climate.gov/enso

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!
 

--Royce Bitzer, January 28, 2021

July 24, 2020

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 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. 

-- Royce Bitzer, July 24, 2020

October 8, 2019

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 (pictures at 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.

-- Royce Bitzer, October 8, 2019

July 31, 2019

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 [https://www.inaturalist.org/people/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.

-- Royce Bitzer, July 31, 2019