The diversity of moths is much greater than butterflies. In his book Discovering Moths: Nighttime Jewels in Your Own Backyard, John Himmelman cites over 2300 species to be found in the neighboring state of Connecticut. The Massachusetts number must be similar. Unfortunately, there are few good written guides. Himmelman’s book is a good start and enjoyable read. The old Peterson Field Guide by Charles Covell is OK, but shows only dead and pinned specimens. This can look quite different from a living specimen at rest. A new Peterson Guide has been published that features living specimens. It is available from one of the authors at http://seabrookeleckie.com/the-new-peterson-moth-guide/
There are some good resources on the web. The first step is to make a good guess as to which family the moth is in. Each family typically has a distinctive outline. Some guides to these outlines can be found at
Another possibility is this key (sort of, although I have not found it useful, because there is no way of easily browsing the results):
One major change in classification is that the Tiger moths, family Arctiidae has been reclassified as a subfamily of Eribidae. So if you think you have a member of that (former) family and you don’t see Arctiidae listed, try Eribidae instead.
Once you have a guess of the family, you can browse photos by family at the following sites and try to make a match:
You might also go back to the bugguide page and use the color and shape plates.
There are very extensive collections of photographs at
John Snyder’s site http://facweb.furman.edu/~snyderjohn/leplist/
Flickr North American Moths backyard Inventory http://www.flickr.com/groups/1057262@N22/
You can’t browse the first one and the second one is not sorted by family, but browsable.
These are good places to double-check for more images of a species you have identified.
Another good way to do that is to do an image search for the species name. This is a good idea so you can get a sense of how variable the species is.