ARBORETUM NEWS (NATURALISTSNOTES)

By the Dark of the Moon

SUNDAY, JUNE 9, 2013

A strange and significant breeze blew out of the southeast throughout our program. This evening we focused on the nocturnal portion of the order Lepidoptera. Although all of the animals in this order are insects, not all of them are moths. The Smithsonian estimates that there are approximately ten times more moths than butterflies, which comprise the rest of the order, on the planet. The tally of moths worldwide is somewhere in the neighborhood of 160,000 species, with many yet to be discovered (I’m looking at you young scientists and naturalists).

The wind was significant for a number of reasons. Moths are less likely to fly on a windy evening, and we had brewed up a odor-filled bait in order to draw in species that continue to eat in their adult forms. On that note, some moths do not eat again after entering their pupa stage. In the case of moths, the pupa stage is recognized as the time they spend within their cocoon (for butterflies it is a chrysalis). They make a cocoon using energy and resources gained during their larval stage as a caterpillar, after which, they cease to eat again and emerge from their cocoon as an adult without any functional mouth parts. Examples of the latter type of moth include some of the more remarkable species of the Giant Silk Moth family. One of which, the Cecropia moth (Hyalophora cecropia), is found in Wisconsin. In order to attract such moths one is best armed with a large white sheet and a black light to illuminate it and draw in moths. Insects being attracted to lights is a common phenomenon that only begins to make sense when one considers a natural night sky. The largest and brightest object will most often be the moon. Being that our tour was on the night of the New Moon, we had the advantage of a lack of competition. Moths, among other insects, use the moon as a navigational tool. Problems occur around artificial light sources because, unlike the moon, artificial sources cannot be trusted when judging by the angle of the light source relative to the direction of travel. The angle gets tighter and tighter, and in the end a spiral crash course occurs. The insect ends up at the source – either through the flame of a candle or attached to the sheet hung by a moth-er (someone who enjoys studying and trapping moths).

Surveying moths is best when conditions are warm and humid. This night was not particularly warm or humid, but I had seen a few large Underwings (of the Catocala family) and a Luna (Actias luna) while hosting a naturalist hike at Blue Mounds State Park the morning of the same day so my hopes remained high. As visitors continued to trickle in, we began to blend a mixture of molasses, beer, sugar and old bananas. This mixture piques the interest of hungry moths beginning to stir as dusk settles towards night. The idea is to find a viscosity that tends not to drip, but can be applied to a surface using an ordinary paint brush. As we mixed, I walked around with a beautiful collection of Wisconsin moths courtesy of the Aldo Leopold Nature Center. Guests were amazed to discover the size of some of their local and fairly common moths. Without further adieu, we hiked a short ways and started to paint our bait onto rocks and stumps. A rectangle of outer bait is recommended to grab and distract other insects, such as ants, from accessing the middle portions of the bait where the moths ideally land.

While waiting for the moths to come, Jim Fitzgerald (the other naturalist on the tour) and I took turns taking visitors through our invaluable native plant garden and the world’s first restored prairie, Curtis Prairie. On our hike we encountered a number of amphibian and avian species sending their audible notes out into the night’s cloudy sky. Notably, a few Cope’s Gray Treefrogs and Willow Flycatchers.

At last, we returned to the bait only to find it empty of any moths. Unfortunately, our night hike came up short on moths. On the other hand, a few new moth-ers may have been born on this night. Guests were intrigued and a number of them left the tour excited to try baiting for moths around their homes.

David Laufenberg, UW Arboretum Naturalist

Located between Lake Wingra and the West Beltline Highway at 1207 Seminole Highway, the University of Wisconsin-Madison Arboretum features the restored prairies, forests and wetlands of pre-settlement Wisconsin. This 1,260-acre arboretum also houses flowering trees, shrubs and a world-famous lilac collection. Educational tours for groups and the general public, science and nature-based classes for all ages and abilities, and a wide variety of volunteer opportunities for groups, families and individuals are available.