The Dec. 17 article by Kelley Bouchard, “Warm days could give birth to winter-moth nightmare on Maine coast,” was great coverage for the invasive winter moth, but surprisingly omitted mention of our native Bruce spanworm.

These are two very similar species, both in the genus Operophtera and are unfortunately almost identical in appearance. As the article discussed, the winter moth (O. brumata) is an invasive species from Europe, but Bruce spanworm (O. bruceata) is native to the northern half of North America.

Since these two are practically morphologically indistinguishable, most entomologists would agree that they should only be differentiated by examining male genitalia (which requires dissection) or through DNA sequencing.

Both of these moths have similar life histories, mate late in the fall, and are both considered defoliators. It needs to be accepted, however, that the natural cyclical processes of native defoliators is an important piece of many animal’s food chains.

For example, a boom year for Bruce spanworm will result in an abundance of larva during the summer, and thus plentiful food for breeding birds. Our Eastern forest bird populations have declined 32 percent over the past half century, which means we need to take necessary precautions and think about the larger ecological picture.

It should also be noted that winter moths have been in Maine longer than the article reported. Surveys done by Joseph Elkinton, et al., detected winter moths in southern coastal Maine during 2005. Fortunately, only Bruce spanworms were collected along interior portions of Maine during their 2007 surveys.

Doug Hitchcox

staff naturalist, Maine Audubon

Falmouth

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