My Honey-Matt has two (very) small lime trees in pots. One fine day I noticed what appeared to be bird poop on one of the leaves. When I tried to flick it off, the poop turned out to be alive. Yes, this is the caterpillar of the Giant Swallowtail butterfly.
Photos by Matt Ball 9/22/2013
More info on these critters here. Even though you won't find them in Sabino Canyon (no citrus trees there), they are simply too bizarre to pass up. And it's my blog, after all : -)