How do you tell one from the other then? Range? Is there a field mark?

As per the 2003 publication by Pogue & Sullivan, E. festivoides is a southeastern species that is found only in Florida, the gulf coast, and the southern Atlantic coast. The wide-ranging species found throughout southern Canada and the northern half of the U.S. is the new species E. alapallida. There are some general differences in wing pattern discussed, but both species are so variable that dissection is required to be certain of IDs where the ranges overlap. A lot of field guides have not been updated to include this new species. The specimen labeled as E. festivoides in Covell, for example, is actually E. alapallida. There is a third species in this complex, described in 2000 and found in the central U.S. and Mid-atlantic states, called E. cornutinis. It is also probably not reliably identified based on photos. The "E. festivoides" photo on bugguide from New Jersey appears to in fact be this third species, but again I don't feel comfortable putting names on these for certain without examining a specimen (and even then some of them are confusing). The reason I moved these is that the only species found as far north as NE PA is E. alapallida, so that eliminates the others as possibilities.

They look all the same to me. :3 So I figured range was the key. Some of the ones I just took photos of look like the Festives here and some like the Pale-so I was way confused-which reminds me, Carbon is not all that far from NJ LOL! Confuse me more. Not to mention the ones that might hitch hike with the tourists. (Pardon my use of common names-spelling the scientific kills me)