Moth Watching

The fact that the vast majority of moths are active only at night, remaining concealed by day, makes it necessary to employ a few special techniques to find and observe them. The main thing to keep in mind is that certain weather conditions are much more favorable for moth activity, with warm, humid, and overcast nights being the best. Little activity is generally seen on cool, clear nights, especially those with a bright full moon.

The simplest way to see moths requires nothing more than a good flashlight. Many species of Sphingidae (hawkmoths) and Noctuidae (owlet moths) may be observed as they obtain nectar from flowers, mainly at dusk and during the first hour or two after dark. Light-colored flowers having a sweet, noticeable odor such as fireweed, bouncing bet, phlox, blazing star, and evening primrose, are the most attractive.

"Sugaring"

Many of the Noctuidae are sap-feeders and may be attracted using the technique known as "sugaring". A bait consisting of brown sugar dissolved in apple juice or beer is applied with a brush to tree trunks along a path at dusk. Sponges soaked in bait may be used in areas with few trees or where sticky tree trunks are not wanted. The underwing moths, with their brilliant red- or yellow-banded hindwings and forewings patterned like tree bark, are attracted to bait from early July into September. It is always exciting to see several of these large and striking moths busily sipping at a bait patch, their eyes glowing in the beam of the flashlight.

Light Sources

The attraction of moths to artificial light sources has been known for hundreds of years and is the major tool for detection and survey work. Simply checking lighted buildings or streetlights can result in seeing many species. However, the sodium lamp, used more often in streetlights and recognized by its orange tint, does not attract moths well.

Field surveys are accomplished with portable light equipment. The Coleman gasoline lanterns used by pioneering lepidopterists have given way to batter-operated fluorescent "blacklights," emitting ultraviolet light in the range most attractive to night-flying insects. A white cloth sheet is hung behind the light source, to intercept and provide a resting place for the moths that are attracted. The use of lights is the only way to locate certain moths not seen at bait or flowers. For example, the Cecropia moth and its giant silkmoth relatives do not feed as adults, having non-functional vestigial mouthparts, as do most Arctiidae (tiger moths) and Notodontidae (prominents).

Whatever technique you use, get out this summer and enjoy observing these fascinating creatures of the night!

Adapted from a 1990 article by Les Ferge.