Black Swallowtail caterpillar

Nice find! Monarch caterpillars feed primarily on Milkweed (though they are found on a couple of other species of plants). They also look a bit different: http://bugguide.net/node/view/979866/bgimage It is not uncommon to find black swallowtail caterpillars in your garden if you grow fennel, dill or parsley. :-) I had a whole lot of them on my bronze fennel last summer.

No, this one is a swallowtail caterpillar. One of the yellow species but check and see which one fits your caterpillar and range.

yep, monarch