Tom Peterson
November 2, 2001
A total of seven new species of butterflies were spotted at Fermilab during 2001, bringing the total number of species sighted to 51 for the past three years. Of those seven new species, four (Meadow Fritillary, Dion Skipper, Gray Comma, and Checkered White) are consider at least somewhat remnant-dependent. The Meadow Fritillary and Dion Skipper in particular are generally restricted to relatively undisturbed natural areas. The variety of habitats--marsh, prairie, old field, and woods--with some of the wetlands and woods being old remnants make Fermilab an outstanding place for finding a good variety of northern Illinois butterflies. Although some rather uncommon butterflies and some remnant-dependent species have been observed on the Fermilab site, no federally or state-endangered species have been seen. The remnant-dependent species are mostly wetland species; no strictly prairie-dependent species have yet been observed in our prairie restorations. One prairie butterfly species, the Meadow Fritillary, was found near the power line and railroad rights-of-way on the eastern boundary of the Fermilab site (more about it below).
2001 was a remarkable year for butterflies. Red Admirals, American Ladies, and Painted Ladies were all more numerous this year than I ever remember. Many other species were abundant this past summer, such as Great Spangled Fritillaries.
In June, I spotted the Little Glassywing Skipper, which is in an informal group of similar skippers along with the Dun Skipper that 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." If you compare my photo of the Dun Skipper with this Little Glassywing photo, you can see what he means. I am 90% sure that my identifications of these two are correct, but I have to admit not 100% sure. Neither species is remnant-dependent.
Another new species seen in June, the Meadow Fritillary, is certainly correctly identified and is a very good find. Fermilab has a colony of them living north and northeast of the garden plots, in ELM-20 (map). Like the Purplish Copper, the Meadow Fritillary is not nationally rare, but it is locally rare in the Chicago area. At most only a few other butterfly monitors in northeastern Illinois report it at their sites. Ron Panzer and Doug Taron classify this as a remnant-dependent species. ELM-20, where the Meadow Fritillaries are found, is an old field area maintained by mowing, which is adjacent to the railroad, a power line right-of-way, and a small wetland. Each of these could have provided a refuge for the butterflies and/or the larval host plants (some species of violets) during the agricultural years. Mel Manner, of the Northern Illinois Butterfly Monitoring Network, reports having seen Meadow Fritillaries in some numbers for a year or two where she monitors (Burlington Prairie) but none before or after. Perhaps they are somewhat mobile, colonizing and dying out from areas. So it seems like we will have to watch this Fermilab population for a few years before concluding that it is stable.
Like last year, ELM-20 is also host to Coral Hairstreaks. I saw Meadow Fritillaries and Coral Hairstreaks on flowers together on June 24, quite a treat for a butterfly watcher!
Early in 2001 I learned 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 a beautiful bright, orange-red, remnant-dependent wetland skipper. It is only found in relatively undisturbed sedge meadows, including only a few sites in the western Chicago suburbs. The Main Injector construction after Ron Panzer's survey, with the Main Injector tunnel excavation and road cutting right across Indian Creek, heightened my interest in seeing whether Dion Skippers still live around Indian Creek. The answer was yes! In early July, following a tip from Bob Lootens regarding where the "good" areas along Indian Creek are, I found a good-sized population of Dion Skippers, especially near the southern-most part of Indian Creek just inside the Main Injector perimeter. The skippers do not yet appear to have moved into the wetland mitigation area, a bit further north, but seem to be restricted to the remaining undisturbed parts of the wetlands. The presence of this skipper indicates that in spite of the Main Injector tunnel and road cutting right through its habitat, enough care was taken that the areas immediately adjacent to the construction remained relatively undisturbed. It is interesting that two other sedge meadow butterflies found at Fermilab which I expected to find living with the Dion Skippers, the Eyed Brown and the Black Dash Skipper, do not seem to live near Indian Creek but are found in other wet areas on site where Dion Skippers appear to be absent. It will be interesting to see whether the Dion Skippers move into the wetland mitigation areas, which are quite close to their present habitat.
The Little Wood-Satyr, which I only glimpsed once last year, is indeed living in the Big Woods. I have seen several and managed to get photos of a few. It is generally a common butterfly, but I have neither found it in large numbers nor found it outside of the woods at Fermilab, where it remains fairly well hidden.
The Big Woods is host to another very nice find for the year, Gray Commas! This relatively rare Anglewing butterfly, which I had only seen once before, at Waterfall Glen Forest Preserve near Argonne Lab, is living in Fermilab's Big Woods (ELM-24, map). Thus, all three Anglewings found in Northern Illinois, the Question Mark, Eastern Comma, and Gray Comma, are found in Fermilab's Big Woods.
A large number of Bronze Coppers could be found in some wet roadside areas in early August, associated with a Polygonum plant species probably serving as the larval host plant. I spotted a Common Sootywing at Fermilab for the first time in August. This butterfly is relatively common in weedy, disturbed areas. I have often seen it along roadsides elsewhere in Kane County.
Two other new species for Fermilab showed up in late September, the Checkered White and the Variegated Fritillary. Both are more common to the south and may be found in this area in late summer. Several Checkered Whites showed up at Fermilab during September, including one at the Prairie Harvest on September 29. This is a native American white (unlike the Cabbage White, which is a European import). September also produced, as expected, a second generation of Meadow Fritillaries at the eastern edge of the Fermilab site and Purplish Coppers near C4 in the Main Ring. The Purplish Coppers were definitely fewer in number this year than last year. I did not find another generation of Bronze Coppers in September. Perhaps the large brood in August was the last for the summer, just an early final generation.
The table below summarizes the new sightings for the summer of 2001.
For more information about the Fermilab butterflies, see the complete Fermilab
Butterfly List.
| New for 2001 | Comments |
| Little Glassywing Skipper | A common skipper which is difficult to distinguish from several other small, common, brown skippers. |
| Meadow Fritillary | A small remnant-dependent fritillary, rather rare in this area, a beautiful new find for the Fermilab site. |
| Dion Skipper | A strongly remnant-dependent skipper seen at Indian Creek in the 1980's is still there! |
| Gray Comma | This relatively rare anglewing is living in Fermilab's Big Woods (ELM-24). |
| Common Sootywing | A common small butterfly in open, disturbed areas like roadsides. |
| Variegated Fritillary | This beautiful, medium-sized butterfly wanders up from the south, not unusual to find it in late summer. |
| Checkered White | Our native, local American white, more common to the South. |
References.
1. "Butterflies through Binoculars, the East," by Jeffrey Glassberg, Oxford University Press, New York, 1999.
