Moth

Yes now is the period with highest numbers so they are all around the gardens. You should correct your spotting.

By the way, there are lots of these in my backyard

Great information - thank you

That's a nice butterfly not a moth, it's most likely Pieris rapae, It's not native to North America and it shouldn't be there but check this link: http://en.wikipedia.org/wiki/Pieris_rapa...