Although no new butterfly species were seen at Fermilab in 2002, there were many interesting highlights. It is still likely that strays providing new site records will occasionally wander through, and perhaps even a local population of a species not yet identified at Fermilab is hiding somewhere on site, but the observations for the past four years have given us a fairly complete picture of the Fermilab butterfly fauna. This summer, I added two previously seen butterflies to the site list, bringing the total number of butterfly species seen at Fermilab to 53. Some interesting observations from the summer of 2002 are summarized here, as well as how two new species were added to our Fermilab butterfly list.
Some Highlights for 2002
A gynandromorph Clouded Sulphur
In prairie near the interpretive trail in June I saw one of the most amazing things a butterflier can see--a striking half-male, half-female butterfly--a form called a "bilateral gynandromorph". It was a Clouded Sulphur, a species for which some females are white. The right side was white female, left side yellow male, a fact that was strikingly obvious when it was flying. (Sulphurs sit with wings closed, so the assymetric color was not at all obvious when the butterfly was resting.) I described the butterfly to Doug Taron, curator for biology at the Peggy Notebaert Nature Museum in Chicago, who is a local butterfly expert. He encouraged me to capture the individual if I saw it again, since it cannot reproduce and so is of little ecological significance, but such specimens are of great interest as objects of study. I did find it again, still in the same area six days later. Hence the photo of the mounted specimen which will be donated to a museum.
As I reported last year, Fermilab has a colony of Meadow Fritillaries living north and northeast of the garden plots, in ELM-20 and TA-4 (map). The Meadow Fritillary is not nationally rare, but it is locally rare in the Chicago area and remnant-dependent. Last year they were sighted in ELM-20 and TA-4, an old field area maintained by mowing, which is adjacent to the railroad, a power line right-of-way, and a small wetland. This year, with help from some excellent butterfly spotters in the Roads and Grounds group, we found Meadow Fritillaries in various places on site. In June, many were flying along the power line and railroad right-of-way just north of the Batavia Road gate (in TA-4 and ELM-19) , and some south of Batavia Road. It is likely that they live along the entire eastern boundary of Fermilab. In September, at least a half-dozen Meadow Fritillaries were spotted in an area nearly two miles away, across C-east Road from the Oak savana in the Bison pasture. (Perhaps Meadow Fritillaries live in the Bison pasture!) In every case, when we found numbers of Meadow Fritillaries they were flying near patches of violets on which the caterpillars feed.
On October 2, Doug Taron introduced 40 Silver-bordered Fritillary caterpillars to the Meadow Fritillary habitat on the east side of the Fermilab site. Bob Lootens and I helped to specify the release area based on where we had seen Meadow Fritillaries and their larval host violets. Fermilab photographer Reidar Hahn and Elizabeth Clements from the Public Affairs Office documented the release in a November 1, 2002, Ferminews article which may be viewed online. The Silver-bordered Fritillary is a wet-meadow fritillary that has declined in Illinois over the past 50 years. We will monitor the population closely to try to understand how the population spreads, whether ours was a good method of introduction, and perhaps we will learn about other factors affecting this butterfly. The first data will be taken in summer, 2003, when the first few generations of adults should emerge.
Mourning Cloaks and Other Woodland Butterflies
On a warm day in mid-April, before the tree leaves were even fully opened, five Mourning Cloaks were flitting around together in the middle of the Big Woods. These hardy butterflies overwinter as adults and may fly any time weather permits. I had an email this past winter from a person who saw a Mourning Cloak on one unusually warm day in January! They are probably the longest-lived adult butterflies in this area. With only one generation per year, the adults that emerge one summer hybernate in a protected place, like in a hole in a tree, and live well into the next summer to mate and lay eggs. In mid-summer the red and black spiny caterpillars are easy to spot since, unlike most butterfly caterpillars, they live communally, in groups of 20 or more. I have found the caterpillars on Willows here on site. Other woodland butterflies were also abundant this year. All three of the local anglewing species--Question Mark, Eastern Comma, and Gray Comma--flew in good numbers in and near the Big Woods. From late August into October, the beautiful, bright orange winter forms of the Eastern Comma and Question Mark seemed more common than usual in and around the woods. Giant Swallowtails, Great Spangled Fritillaries, and Banded Hairstreaks also appeared at the woods edge, as usual.
In, 2001, I mentioned that Ron Panzer, a Chicago area naturalist, reported seeing Dion Skippers along Indian Creek in the late 1980's. Indian Creek runs through the center of the Main Injector area and south past the Batavia branch of the Illinois Prairie Path on the southwest boundary of the Fermilab site (map). The Dion Skipper is only found in relatively undisturbed sedge meadows, including only a few sites in the western Chicago suburbs, so is quite an interesting find for Fermilab. In 2002 the Dion Skippers were very abundant near Indian Creek again, and one was seen in a sedge meadow within the Main Ring.
Bronze and Purplish Coppers
Only a few Bronze Coppers were spotted this year, and there were never large numbers of Purplish Coppers. But the Purplish Coppers were widespread and persisted well into October. The Purplish Coppers were found in several new places along Wilson Street, along Road A, and along Road C. Both Bronze and Purplish Coppers seem to be quite widespread and well-established on the Fermilab site. Fermilab's Coppers are a joy to see every year.
Newly listed for 2002--Orange Sulphur and Northern Broken-Dash skipper
One new species for the site list, the Orange Sulphur, resulted from separating it from the very similar Clouded Sulphur. Although these two butterfly species may interbreed, and specimens intermediate in coloration between the lemon-yellow Clouded Sulphur and orange-yellow Orange Sulphur make identification difficult at times, many individuals of each species are clearly present. So we should take credit for having both of them on site. The Sulphurs were especially abundant this fall, and even now in early November they may be seen flying on sunny days.
The other new species added to the site list, the Northern Broken-Dash (a skipper), was also previously seen but was not distinguished from another species. The Northern Broken-Dash is in an informal group of similar skippers along with the Dun Skipper and Little Glassy Wing, which Jeffrey Glassberg (see ref. 1, below) and other lepidopterists refer to as "the witches". Glassberg says, "All of the witches are generally common. [Where they fly together in large numbers they can create] an unparalleled opportunity to misidentify thousands of butterflies in a single day." I believe they are called "the witches" because it is so difficult to tell which is which. With the help of some good photos, I was able to confirm that indeed some of our Witches are Northern Broken-Dashes. What I now know are Northern Broken-Dashes are often found in the field just west of the Big Woods. They seem to be fairly local, while the very similar Dun Skippers are more scattered over the Fermilab site.
Newly listed for 2002 Comments Orange Sulphur Separated the Orange Sulphur from the Clouded Sulphur in the species list. Both are common and breeding on site. Northern Broken-Dash A common skipper which is difficult to distinguish from several other small, common, brown skippers. I had lumped it with the Dun Skipper, but with the help of some good photos was able to confirm the identification of some "Dun Skippers" as Northern Broken-Dash.
1. "Butterflies through Binoculars, the East," by Jeffrey Glassberg, Oxford University Press, New York, 1999.
Butterfly Data - Peak Count Data for 2002 - Map of Fermilab