I really need some help here. I just spent about an hour and a half on various websites and with the two butterfly guides we have - and I give up. This was perched on a pot outside the door one cool morning. I really thought it was dead, but when I went back hoping for a better pic, it was gone. I've exhausted all the possibilities I can find of yellows and whites - can anyone help? Even help me narrow it down? All I can tell you is what it's NOT. The markings appear rather indistinct - but the rest of the picture seems to be in focus.
Thanks for pointing me in the right direction. I briefly considered that it might be a moth, but I thought the body and antennae weren't heavy enough. Would you mind sharing with me what tipped you off? I don't think hemlock looper is quite right, from the (few) pictures I could find. But I think you're on the right track. I'll keep looking.
It may be very difficult to key the moth to species. You may have to be content to refer to it as a Geometrid Moth (that's the family that hemlock loopers belong to) There are hundreds that belong to that family and many look very similar. I'm familiar with most moth families ( I did two entomology courses in University) so that is how I narrowed it down, but as mentioned, moths rest with winds open, most butterflies are closed (except when they are trying to warm up, then they may rest with their wings open).