Tom Peterson
November 4, 2002
No new butterfly species were seen at Fermilab in 2002. Although it is still likely that strays providing new sight records will occasionally wander through, and perhaps even a local population not yet identified at Fermilab is hiding somewhere on site, 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. I conclude with a few recommendations to the ELM committee.
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 recognize as 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. |
Some highlights for 2002
Big Woods
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. Through the summer
I saw the three anglewing species--Question
Mark, Eastern Comma, and Gray
Comma--in good numbers in and near the Big Woods. Giant
Swallowtails, Great Spangled
Fritillaries, and Banded Hairstreaks
also appeared at the woods edge, as usual. Particularly the savanna-like
area west of the woods is excellent butterfly habitat. Encouraging
a blending of woods into prairie via a savanna-like area, rather than a
sharp woods-prairie edge, would benefit these and many other butterfly
species. My strongest recommendation to the ELM committee would be
that we encourage savanna-like transition zones between our prairie restorations
and adjacent woodlands.
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 (on
the Clouded Sulphur page) of the mounted
specimen which will be donated to a museum.
Indian Creek
In 2001, I mentioned that Ron Panzer, a Chicago area naturalist, reported
seeing Dion
Skippers along Indian Creek in the late 1980's and that the Dion Skippers
are still there. The Dion Skipper is only found in relatively undisturbed
sedge meadows, including only a few sites in the western Chicago suburbs,
so it is quite an interesting find for Fermilab. In 2002 the Dion
Skippers were very abundant near Indian Creek again. The Indian Creek
area is also host to large numbers of Northern
Pearly-eyes, which thrive in the open, wet woods.
Main Ring Sedge Meadows
Some sedge meadows within the Main Ring, both north-west of the ring
center and south-west of the ring center, are host to some very local and
remnant-dependent sedge butterflies such as the Black
Dash and Eyed Brown. This
year for the first time I also spotted one Dion Skipper in a sedge meadow
within the Main Ring; perhaps as those sedge meadows improve the Dion Skippers
will move into them in larger numbers. Prairie and old field areas
in the western part of the Main Ring near the wooded areas host Acadian
Hairstreaks and Delaware Skippers.
The quantities of these butterflies are never large, but this wet prairie,
sedge and wooded area is one of the best butterfly habitats at Fermilab.
Meadow Fritillaries
As I reported last year, Fermilab has a colony of Meadow
Fritillaries living north and northeast of the garden plots, near ELM-20
(map).
Like the Dion Skipper, the Meadow Fritillary is not nationally rare, but
it is locally rare in the Chicago area and remnant-dependent. 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 and also south of Batavia Road.
It is likely that they live along the entire eastern boundary of Fermilab
(in TA-4). In September, I found at least a half-dozen Meadow Fritillaries
living across C-east Road from the Oak savana in the Bison pasture.
(Perhaps they also 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 Ferminews article (http://www.fnal.gov/pub/ferminews/ferminews02-11-01/p3.html).
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 May, 2003,
when the first generation of adults should emerge. We will want to
be careful about mowing this release area next year; not mowing it all
at once would be beneficial.
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; I doubt that any special consideration needs to be
given to mowing times for the various locations where the Coppers have
been seen. In fact, whatever we have done for the past several years
seems to be working quite well for the Coppers.
Conclusions
1. My strongest recommendation to the ELM committee would be
that we encourage savanna-like transition zones between our prairie restorations
and adjacent woodlands. Perhaps such a transition zone could be encouraged
either by thinning the woods adjacent to the prairie or by allowing some
spreading of brush and trees from the woods edge into the prairie by not
burning right to the woods edge.
2. The sedge meadows within the Main Ring and in the Indian Creek
area host several of Fermilab's rarest and most fragile butterfly species.
These seem to be relatively good-quality wetlands.
3. The Silver-bordered Fritillary (and Meadow Fritillary) areas
(ELM-19, ELM-20, and TA-4) would benefit from staggering the mowing schedule
among parts of the habitat. It seems possible that the oak savanna
in the Bison pasture may be a home for a Meadow Fritillary population.
We should check there for violets in the spring.
References.
1. "Butterflies through Binoculars, the East," by Jeffrey Glassberg, Oxford University Press, New York, 1999.
