Thanks for the response.

I was lucky to be carrying multiple lenses with me at the time, but I was leaning over the water, so I didn't have a lot choices about angles. Does this picture help. I took quite a few, but they mostly look the same.

The third picture is of a male Pearl cresent ( underside ) as shown in the Kaufman guide. The dorsal picture is that of a Northern cresent according to the Kaufman guide. Need expert to explain what is shown in the Kaufman guide.

I think you understood, but just to be clear, all three pictures are of the very same insect. The second picture would be last in the sequence after it turned around and walked to a different part of the leaf. The color of the leaf looks different just due to exposure, white balance, etc. The sun was really bright and combined with the water it was difficult to see.

I understand about the butterfly. My interest is hopefully to get some Bugguide butterfly experts to give feedback on what I believe is an error in the Kaufman guide.

I don't think there is an error, the illustrations look correct, but they are confusing. The two species (or is it three? four? - or - some think it is only one!) look so similar, and are so variable in pattern (with lots of overlap), that it is very difficult in a small field guide to show the range of variation and the differences well. However, indeed male Pearl Crescents often do not look like the one shown in the guide (on the upper side anyway), but rather they usually look more like the male Northern that is shown (the male Pearl shown actually has a pattern much like a female - and is probably an early spring generation individual). On the flip side, there is no female Northern shown, and they usually look more like female Pearl Crescents than they do like like Northern Crescents. None of the diagnostic characters that books list for the two work all the time, which makes it very difficult. Where they are found (including habitat type), and the time of year are often good clues as to which is which. In Pearl Crescents of the Northeast and East, the males usually have dark antenna tips, while those of Northerns everywhere have orange tips. This doesn't work on females, and it doesn't work for males further west. All the pattern traits usually mentioned are usefull as "rules of thumb", but they often don't work for individual butterflies that often "break the rules". Even so, they behave as two totally different species, and in the field, when observing a population, there is usually no problem figuring out which you are looking at. The two are rarely found together in the same place.

Thanks David - I thought the "variability factor " would be involved along with range and habitat. May the butterflies be with you, Henry.