I was looking at some tiny Erigeron daisies when I noticed a little speck of detritus in the center of one. The speck was brown and had bits of daisy-petal stuck to it. It turned out to be a minuscule emerald moth caterpillar (Synchlora)!
These fellows nip off bits of the flowers they're browsing and stick the bits onto themselves for camouflage. I found a very sweet story about an enterprising cousin of this caterpillar: