April 10, 2017

Look out for Red Admirals! Large numbers of these butterflies have been migrating northward across the upper Midwest and southern Ontario, Canada in the last few days in the wake of a strong flow of warm, moist air from the Gulf of Mexico. Some observers have also seen either Painted or American Ladies flying with them. This wave of butterflies has appeared over a wide area of the upper Midwest from northeastern Kansas to Minneapolis, central Iowa, and southwestern Wisconsin within a relatively short time, between April 6 and April 9, suggesting a sudden incursion from elsewhere. To further support this possibility, there has been one report of a steady stream of northbound Red Admirals and Painted Ladies throughout the day on April 8 in Polk County in central Iowa.

Painted Ladies have been on the move this spring. Their first generation may have gotten started in southern California during the enormous February-April bloom of desert annuals that provided abundant food plants for their caterpillars. Although there didn't seem to be a widespread Painted Lady outbreak across California - instead I received reports of small numbers there for the most part - there have been scattered reports of large outbreaks in the western U.S. and Canada between early April and now. These include:

Nevada southwest of Las Vegas: April 3 - 5, 2017. On April 3 and 4, Painted Ladies were flying from west to east at rates of 5 per minute or more for periods of 4 and 6 hours respectively. Activity had greatly decreased on April 5, with only about 10 spotted during a half-hour period around 10 am.

Medford, Oregon: May 2, 2017. An observer completed a point count of Painted Ladies at 2:30 p.m., observing 168 butterflies per hour flying generally east-southeast to west-northwest (the starting time wasn't mentioned).

Albuquerque, New Mexico: Mid- to late May 2017. Painted Ladies were present in large numbers here since perhaps the middle of May. Hundreds were seen nectaring on a linden tree on May 26.

Alberta, Canada, between Red Deer and Edmonton (south to north) and Alder Flats and Innisfree (west to east): Painted Ladies have been abundant in this area since about June 5, and continued to be as of June 17.

Northwest Iowa, Orange City and near Calumet: June 15. Fresh Painted Ladies were locally abundant in Orange City and also at Iowa State University's Northwestern Research Farm south of Calumet. About 20 were seen within a half hour at each location. Another observation suggested that this abundant population was somewhat localized on June 15. Two other sites near Newell, in west central Iowa about 60 km southeast of Calumet, had only a few or none on the same date. Nor were Painted Ladies present farther east in the Mason City, Eagle Grove, or Ames areas on June 16, although weather conditions were likewise favorable.

If you see Painted Ladies in your area, including larger numbers such as described in the above reports, please report them here or at http://vanessa.ent.iastate.edu.

If you live in Iowa, have you been seeing the abundant Red Admirals that have emerged or arrived within the past 10 days? Following a rain in the Ames area on June 13, Red Admirals were suddenly all over the place the next day. I went outside on the Iowa State University campus on the afternoon of June 14 and saw dozens of fresh new ones nectaring in a linden tree. Many more are present now than there were before this outbreak occurred.

Another place I saw many fresh ones was at Orange City on the morning of June 15. These seemed to be localized within a limited area of northwest Iowa, because I saw only one butterfly near Sutherland and none near Newell on the same day. The Orange City butterflies, however, didn’t seem to have been induced to emerge by recent rainfall, since that part of the state missed out on the rain that reached most of Iowa on the 13th.

I also received a report of 200 nectaring in a linden tree near Marshalltown, also on June 15. There was also a "huge" Red Admiral hatch near the Iowa Arboretum, just west of Luther, during the same week. Their numbers were "incredible!"

Who else has been seeing them, and where? These large numbers seem to be occurring in some parts of Iowa and not others. For example, on June 16, I was in the Mason City and Eagle Grove areas (north-central) and didn’t see any near Mason City, and only two near Eagle Grove, even though the weather conditions were as favorable then as they had been in northwest Iowa the day before.