It's been a wild year for butterflies in the Chicago area. Heat and drought seem to be the catchwords of the year. The season got off to an extraordinarily early start. It's not all that unusual to see a few butterflies in March, as species like Mourning Cloaks that hibernate as adults sometimes venture out on warm days. The prolonged hot spell in March brought a lot of species out, many over a month early. These Spring Azures were photographed at Bluff Spring Fen on St. Patrick's Day.
As the season settled in, the east central part of the US and Canada was overrun by an enormous population explosion of Red Admirals. In April the wave of Red Admiral migration crossed northern Illinois, with numbers about ten times their normal levels. As impressive as that was, the huge migration was even bigger in eastern Canada, where it was estimated that hundreds of millions of the butterflies were passing through.
Not surprisingly given the early and very warm season, 2012 saw the influx of several butterfly species that normally fly further to the south. Pipevine Swallowtails, Dainty Sulphurs (photo below), and Sachem skippers were all conspicuous in the Chicago area for much of the summer. These species are typically either rare or absent this far north. It will be interesting to compare data collected by the Illinois and Ohio butterfly monitoring networks to see if similar trends were observed in both of these states.
The news wasn't all good. The drought seems to have taken a toll on some of the region's rare butterflies- those species that require remnant prairies or wetlands. The Nature Museum's Butterfly Restoration Project made very little progress this year due to the very low numbers of these species that we encountered. Species that were present in very low numbers this summer included Silver-bordered Fritillaries, Baltimore Checkerspots (photo below), and Regal Fritillaries. With luck, conditions will be more favorable in 2013 and their numbers will rebound.