There are two ways to attract a butterfly. One is to put out a bait consisting of elderly fruit--bananas are particularly good--mixed with molasses, beer, and yeast. The other is to piss on the ground.
Either smell, urine or rotting fruit, is practically irresistible to your average lepidopteran.
I learned of the inelegant tastes of these elegant insects from Susan Borkin, an entomologist on the staff of the Milwaukee County Museum, during a two-day workshop on butterflies and moths that she taught last month at the University of Wisconsin at Milwaukee Field Station in Saukville, Wisconsin.
Our class of 20 was made up mostly of professional biologists--botanists, ecologists, and others--who wanted to expand their knowledge of insects. Several worked for the branch of the Wisconsin Department of Natural Resources that oversees the state's system of natural areas. I was one of the few amateurs and also the only non-Wisconsinite in the group.
The nucleus of the field station is an old farmhouse where we ate and slept. We had our classes and studied specimens in a separate building.
Wisconsin is a state with many grand traditions. John Muir, the founder of the Sierra Club, was from Wisconsin, and Aldo Leopold, one of the philosophical fathers of the contemporary environmental movement, taught at the University of Wisconsin.
Wisconsin is also famous for good, hearty food and beer. Our meals were excellent, scrambled eggs for breakfast, ham and German potato salad for supper. The refrigerator was filled with Leinenkugel's long necks available for 30 cents a bottle. I couldn't help reflecting that if the University of Illinois was running this program, we would have drunk Kool-Aid, with iced tea available for those who wanted to try life in the fast lane.
Not that we had much time to sit around and drink. Susan started us out the first morning with a lecture on the evolution of the lepidoptera. The name means scale winged. Look at a magnified wing of a butterfly or moth, and you can see that the colors and patterns reside in tiny scales attached to a transparent membrane that forms the wing.
Lepidoptera undergo a complete metamorphosis in the course of their lives, changing from wormlike caterpillars to winged adults. The caterpillars have chewing mouthparts. Most are vegetarian, but a few are carnivorous. The adults eat with a proboscis, a long flexible hollow tube like an elephant's trunk that can suck up flower nectar, urine, or fermenting fruit.
After hearing the generalities, we adjourned to a room full of 20-power binocular microscopes and began keying out some specimens.
Biologists use dichotomous keys to identify specimens of everything from mosses to owls. A key presents a series of choices. Does your specimen have only four functional legs or are all six legs made for walking? If four is your answer, move on to section B in the key. If six is correct, move to section C. Each of those sections will give you two more choices.
If you make the right choice at every step, you arrive at the correct identification. Make the wrong choice early, and you end up like LBJ in Vietnam, with each subsequent choice leading you further and further from the truth.
Fortunately, I had a book called Butterflies of Wisconsin by James Ebner to guide me. Only 138 species of butterflies have been recorded in Wisconsin--compared to over 700 in the whole of North America--so Ebner's key was quite simple to use.
And it was fascinating to see these specimens under 20 powers of magnification. I could see the proboscis coiled up under the head and note the shape of the antennae: thickened at the tip in the true butterflies, hooked in the group called skippers. The reduced forelimbs in the butterflies with only four walking legs are actually sense organs. The insects, "taste" their food in advance by scratching at it with the claws at the tip of those legs, and females scrape at leaves before laying eggs to be sure they are placing their young on the proper food plant.
After lunch, we left the lab and set out to do some collecting. This was great fun for several reasons. The field station is surrounded by a variety of habitats, each with its own special contingent of butterflies. We discovered least skippers and red admirals in an old field, checkered Baltimores in a sedge meadow, pearly eyes in the woods.
Our most exciting find was a bog copper, a rare species whose caterpillars live on cranberries. We found it in the middle of Cedarburg Bog, which is right across the road from the field station.
Cedarburg is one of the largest and most pristine bogs in eastern Wisconsin and the most southerly known example of a string bog, a type of peatland more typical of the arctic than of southern Wisconsin.
I also loved the collecting because it gave me a chance to run through the fields waving a butterfly net. There was a time when a fondness for birding was enough to establish your reputation as a true eccentric. But lately, birding has shown signs of becoming rather depressingly mainstream. A couple of months ago, Time magazine discovered it; and the new Life devotes several pages to a review of top birding spots. Bird-watchers are becoming as ordinary as bass fishermen, but a butterfly net is still the mark of a loony.
Of course, there are ethical questions involved in collecting. What if the bog copper you just scooped into your net is the last female in the local population? What if she was just about to start laying eggs and by capturing her, you have prevented her from reproducing?
As more and more natural areas are bulldozed out of existence, these questions are becoming less and less theoretical. Habitat-restricted insects like the bog copper rise or fall with the ecosystem they depend on, and while collecting may destroy only a few individuals, it could make a difference in a population that is already under severe stress.
However, an entomologist like Susan Borkin can make a strong case for the necessity of collecting. Our knowledge of the distribution of insects, even insects as conspicuous as butterflies, is very sketchy. A specimen captured, killed, and pinned to a board can increase our knowledge and ultimately benefit the species by helping us make more intelligent decisions about what land needs to be protected.
So, as with many ethical questions, we discover that a simple rule will not suffice. It is not good to murder rare butterflies to decorate the walls of your den, but under certain circumstances, in carefully limited amounts, collecting may be better than not collecting.
We collected until dinnertime, running up a total of 21 species. After dinner, we lingered over good talk and Leinenkugels until the sun went down and then set our snares to capture moths.
Moths are a much more numerous and varied group than butterflies. There are about ten species of moths for every butterfly species. Most of them are night flyers, although some are active during the day.
We set two kinds of traps for them. One consisted of a black light placed over a jar of ethyl acetate. Ethyl acetate is the main active ingredient in fingernail polish remover and a pretty effective insect poison. Lights attract moths because the insects orient themselves by the moon, so they have a positive tropism toward light.
Our other trap was the smelly mixture of bananas, yeast, and beer I mentioned in the opening paragraph of this story. We walked through the woods and every once in a while, slathered a tree trunk with the stuff, using a four-inch paintbrush for the job.
Our efforts netted us a half dozen species of moths and at least four million other insects, ranging from caddis flies three inches long to about a third of the mosquitoes in Ozaukee County.
After two days of systematic instruction and practical demonstration, I no longer feel intimidated by the complexities of identifying butterflies. I have a lot to learn, but at least I have some sense of what I have to learn. Now I need to get out to a biological supply house to buy myself a net.