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Small tan moths at outdoor lights on mild November to January nights

November to January

On mild nights from mid-November into January, small tan moths gather at outdoor lights across eastern Massachusetts while their nearly wingless mates crawl at the base of trees and up the trunks. What looks like one moth is a group of look-alikes, and even entomologists cannot tell the two Operophtera species apart in the field without DNA.

Why this time of year

Most moths are long gone by then, which is the whole oddity: these emerge from the soil when it turns cold and fly whenever an evening is mild. In the 2025-26 flight season arborists reported flights in Brookline, Wellesley, Newton and Sturbridge, in groups of 30 to 50 moths at a time.

How to notice it

  1. On a mild evening above freezing between mid-November and January, step outside after dark and check an outdoor lamp, a lit window or holiday lights for small tan or light-brown moths circling.
  2. Now look down. Check the ground and the lower foot or two of nearby tree trunks for the females: gray, moth-shaped, with wings reduced to stubs, crawling rather than flying.
  3. Do not try to pin down the species by eye. Note roughly how many moths you see and whether it feels like a big night or a quiet one.
  4. If you want a name for it, say winter-flying moth rather than winter moth, since Bruce spanworm and fall cankerworm males look the same at a glance.

Try this with kids: Can you find a moth near the bottom of a tree trunk that is crawling instead of flying, even though it is a moth?

biological control: releasing a natural enemy of a pest, here a parasitic fly, to hold its numbers down without spraying

Sources

  • umass.eduUMass Extension, January 23 2026. Arborists reported flights of moths in Brookline, Wellesley, Newton and Sturbridge MA, on Martha's Vineyard, and in Cumberland RI in November and December 2025; groups of 30-50 moths were reported; over 525 moths counted in a 3.3 mile stretch on Martha's Vineyard; over 1,000 iNaturalist reports of POSSIBLE winter moth, Bruce spanworm or fall cankerworm across the region; identification to species is not a simple process; Dr Jeremy Andersen reports western Rhode Island is experiencing a true winter moth outbreak with thousands caught in traps, very different from the dozens to hundreds reported in parts of Massachusetts
  • umass.eduWinged males are light brown to tan, are strongly attracted to lights and can often be found flying around outdoor lamps or holiday lights, and emerge from the soil mid-late November and may be active into January whenever air temperatures are mild, typically above freezing; females are gray and almost wingless (brachypterous) and are usually found at the base of trees or scurrying up tree trunks; adult males of the two Operophtera species are extremely difficult to distinguish and DNA analysis is the only known accurate method for differentiating these two species
  • umass.eduSeptember 2018. After 14 years of releasing the parasitic fly Cyzenis albicans, UMass entomologist Joseph Elkinton reports they successfully converted winter moth into a non-pest, presumably on a permanent basis, with moth and fly settling at lower densities rather than the moth being eliminated

Checked against these sources on September 15, 2026.

In the guide for November, December, January

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