A light in the dark of night lures exciting moth species
August 16, 2020
NATURE
Jim McCormac
Ohio’s moth fauna is incredibly diverse. At least 2,000 species have been documented, and scores of others await discovery.
I once heard an expert on “micro-moths” say that if we could find all of those largely ignored miniature moths, Ohio’s moth list might double.
Silkworm moths are lepidopteran antonyms to micro-moths ‒ most are “macro-moths,” with some species reaching the size of bats. Others are much smaller, but a commonality is their spectacular appearance.
A recent nocturnal foray at the Highlands Nature Sanctuary in Highland County west of Chillicothe produced numerous sightings of jumbo silkworm moths.
The 2,900-acre Highlands Nature Sanctuary is the core of the Arc of Appalachia’s nearly 7,000 acres of protected lands. The private conservation group preserves some of the best natural areas in southern Ohio.
When we began plotting our nocturnal mothing expedition, I knew it would be good. Plant diversity and intact ecosystems foster moth diversity. The primary driver of moths’ four-part life cycle — egg, caterpillar, pupa, adult — is the caterpillar.
Most caterpillars are finicky about the plants they consume. Some species eat only one type of plant. A plant required by a particular caterpillar is its host plant. An area rich in flora, including species such as oaks — major host plants for scores of caterpillars — is likely to produce blizzards of moths.
Shortly before sunset on July 17, I met up with Nancy Stranahan and Brent Charette of the Arc of Appalachia, and moth experts John Howard and Kim Banks in the midst of the Highlands Nature Sanctuary. We quickly set up several mothing stations, each consisting of a white sheet illuminated by lights. Mercury vapor and ultraviolet lights work best as attractants.
And, like a moth to a flame, in they came. Moths’ attraction to light is known as positive phototaxis. There are several theories as to why moths are smitten with light, but the answer is unclear. To moth researchers, the creation of temporary light sources in areas of interest is the best way to survey moth populations.
As the night progressed, the mothing improved. Along with commoners, many unusual species appeared. Notable was an oddity called the Harris’ three-spot. Five showed up, about equaling my previous sum total over 20 years of mothing.
But as always, we eagerly awaited the appearance of silkworm moths. One never gets jaded to these spectacular insects. First in were rosy maple moths, resplendent in furry suits of pink and yellow.
As the night wore on, Io moths began to appear. At rest, these largish silkworm moths look like a plain yellow wedge topped with antennae. Tap one with your finger, and voila! The moth flicks its forewings open to reveal large eyespots on the hind wings. These pseudo-eyes might serve to frighten investigating songbirds.
Around 1:30 a.m., giant silkworm moth traffic increased markedly. This uncivilized schedule is typical — the hours between midnight to 4 a.m. often seem best for them. Hardcore mothing is for night owls.
We posed the accompanying image around 2 a.m. From lower left, clockwise, it includes tuliptree silkmoth, regal moth, Luna moth, and imperial moth. Many specimens of each appeared. We could not coerce nearby Io, Polyphemus or rosy maple moths into the photo.
Silkworm moths and moths in general are barometers of ecological health. Lots of moths mean healthy ecosystems. Light and chemical pollution, invasive predatory insects, loss of host plants and overall development have taken severe tolls on moth populations.
Moths underpin food webs critical to the survival of bats, birds and inestimable numbers of other insects. To adequately conserve them — and overall ecosystems — we must protect large blocks of habitat, such as the Highlands Nature Sanctuary.
Naturalist Jim McCormac writes a column for The Dispatch on the first, third and fifth Sundays of the month. He also writes about nature at www. jimmccormac.blogspot.com.