As I write this, your 2001 counts are just arriving for publication. It's too soon to analyze the results, but based on reports from around the country, including "Clouds of Butterflies" in the last issue of American Butterflies, I'm expecting lots of interesting observations of the American Lady, Painted Lady, and the not at all similar but closely related Red Admiral.

     If you're like me, you'll turn to the 2001 count report (available next spring) to see how much your personal experiences of these species were shared by other butterfliers. In the meantime, I'd like to reflect backwards on what past count data say about these butterflies.

     One thing is clear -- each year is different, as these species' abundance and distribution fluctuate a great deal. The graph above shows the number of counts that reported any individual(s) of these species in North America north of Mexico each year. At first it looks like a jumble, and there's some truth to that, as fluctuations are inherently unpredictable. But some patterns emerge.

     The Painted Lady had the sharpest changes -- from the lowest occurrence (17% of counts, in 1999) to nearly the highest (75% in 1992). The Red Admiral varied from 40% (1996) to 76% (1985), and American Lady from 21% (1982) to 52% (1994). You might be surprised that Painted and American Ladies have the same long-term average occurrence (37 vs. 38% of counts for 1982-2000). The Red Admiral is much more consistently widespread (59% of counts in that period).

     A way to compare how much these percents vary is something called a coefficient of variation. I'm not going to explain how this is calculated, but suffice it to say that the larger the coefficient, the more those percents are varying -- which means more fluctuations in abundance for you counters to experience. True to form, the Painted Lady has the highest coefficient (44) while American Lady and Red Admiral had much lower ones (23 and 17, respectively).

     What this means for you counters is that, on average, the Red Admiral is more consistently found than either the American or Painted Lady. But in some years, the Painted Lady rivals the Red Admiral for continent-wide occurrence. However, the Painted Lady also has years of remarkably restricted distribution and numbers, while the American Lady is more consistently found than that from year to year.

     But it's only by counting your butterflies in your area that you can determine how your experiences fit into the larger picture of these butterflies' lives and exploits.

Copyright © 2001 by the North American Butterfly Association, Inc. All rights reserved.