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YEAR OF THE MOTH

When we stroll the trails around Hilton Pond, we're always delighted to come across a plant or animal we recognize, but often we encounter something we've never seen and for which we don't know the name. One could spend a lifetime exploring the small 11-acre tract that makes up Hilton Pond Center and scarcely make a dent in identifying all the local flora an fauna--much less understanding how all those organisms relate to each other and the environment. We've devoted the past 45 years or so to nature study--25 of those at the Center--and there are entire taxonomic groups of macroscopic plants and animals asbout which we still know almost nothing. (Even more mind-boggling is the property's vast complement of microscopic creatures that are surely almsot infinite in number AND invisible to our eyes.) We're pretty good at birds and trees and small mammals and wildflowers but are just beginning to identify dragfonflies and spiders, and someday we really ARE going to have to buckle down and learn the grasses. This year, however, we think we'll start working a little harder on moths.

All text & photos © Hilton Pond Center

We were reminded late one afternoon this week how much we have to learn about moth taxonomy when we gazed out the kitchen window of the old farmhouse at Hilton Pond Center. We were looking at a couple of Northern Cardinals engaging in rather frantic courtship behavior in a distant shrub. Suddenly we realized another pair of organisms was much closer--two white moths clinging to the outer surface of the window glass. We had seen this species before but had never determined exactly what they might be, so we were glad the pair remained motionless and gave us time to take a few photos and consult our field guides.

We suppose we ought not feel too guilty about not knowing moths very well. Butterflies--which share the insect order Lepidoptera with moths--have many devotees, probably because these scaly winged creatures are colorful visitors of meadows, woods, and gardens. Far fewer people are interested in or knowledgeable about moths, probably for two reasons: 1) The vast majority of moths are cryptically colored--especially when their wings are folded; and, 2) Moths are creatures of the night, and try as we might we humans just aren't very good at seeing in the dark. One way to get better at understanding moths is to make them come to us, and that may be what happened with the white ones on the kitchen window; these two probably were drawn by kitchen lights the night before.

It's also possible just the female was attracted to light and the male followed her in. Lacking bright colors and unable to capitalize on behaviors made visible by daylight, nocturnal moths resort to different strategies for locating mates. Perhaps most famous is the female moth's production of pheromones, potent aromatic chemicals that waft on the wind. The male's feathery antennae are covered by chemical receptors so sensitive they can be triggered by a single pheromone molecule, thus enabling the male to home in on a potential mate. The two photos above--one of the moth's ventral side taken through the glass, and one of the dorsal taken from outside--are of the male; his antennae are noticeably broader than those of the female (below left). Speaking of broadness, the female's abdomen is much more rotund--undoubtedly because it is filled with developing eggs almost ready for deposit. The male's abdomen is slimmer and is tipped by a tuft of white fuzz that hides his reproductive structures.

The moths on the window never moved while we photographed them, and we could have taken more photos had the setting sun not robbed us of natural illumination we prefer to use. As darkness fell, we stowed our camera gear, turned out the kitchen lights, and went off to the Center's field guide library to see if we could actually identify our two white moths.

Although there are plenty of new butterfly guides to help folks learn the daytime lepidopterans, moth manuals are few and far between. The old standard is Covell's Field Guide to Moths of Eastern North America, but we find it lacking because it only includes photos of pinned, spread-winged specimens from collections rather than depicting live moths in natural poses. (To make matters worse, many of the images are black-and-white--even for moths that aren't.) These days the most up-to-date moth guides are on the Web; it's too bad even the good sites are incomplete and lacking in useful tools to help identify a moth to species.

Fortunately, our two white moths on the kitchen window were so distinctive they could be identified readily from Covell and by comparing them to photos on several Web sites. Turns out they were Spilosoma congrua, the Agreeable Tiger Moth. This species has few to several black spots on otherwise pure white forewings; white hindwings bear only one or two spots. (The four closely related white tiger moth species may have either many more spots or none at all, but this character is highly variable.) In our Agreeable Tiger Moths the bases of the forelegs are covered with orange fuzz, giving the impression of a bright stain on the chin. In the equally common Virginian Tiger Moth, S. virginica, this stain is absent but typically there are orange spots on the upper surface of the abdomen. Inch-long Agreeable Tiger Moths are common across the U.S.--especially eastern--from April through October. According to Covell, females lay eggs on various herbaceous plants, including Dandelion and Pigweed.

Our ID of the two Agreeable Tiger Moths on the window at Hilton Pond Center bring our Moth Checklist to a grand total of . . . 11 species (including one caterpillar). Obviously, we have many more kinds of moths at the Center--leaving a porch light on in mid-summer quickly provides proof of this--so the low number is a reflection of our previous lack of attention to the intricacies of moth identification. We promise to do better. According to the Chinese calendar, 2006 is the "Year of the Dog"; for us it's gonna be the "Year of the Moth."

All text & photos © Hilton Pond Center

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by Bill Hilton Jr., executive director of
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