Tom Peterson
November 4, 2002
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.
Meadow Fritillaries
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.
Silver-bordered
Fritillaries
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.
Dion Skippers
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. |
References.
1. "Butterflies through Binoculars, the East," by Jeffrey Glassberg, Oxford University Press, New York, 1999.
