Looked out bathroom window a few days ago to see yellow-and-black butterfly sipping from lilacs. Guessed it was a viceroy, since it didn't look like a monarch. (You might tell from this that I don't know from butterflies!) However, there are more things in heaven and earth, Horatio... With much novice frustration at hunting down wildlife in guides that cover at least half the country, I was inspired to search "massachusetts butterflies. In only a few minutes I had nailed it as a probable Eastern Tiger Swallowtail, by the black streaks extending from the leading edges of the wings.
AND the result of that brief web hunt gave me, as lagniappe, a new site to poke around in!