Insect and Spider Identification: CLOSED: Is this a swallowtail caterpillar, 3 by 1alh1

1alh1 wrote:
I found this guy/gal resting on a gas plant (dictamnus) leaf this afternoon. I remembered that some caterpillars disguise their appearance to make themselves less attractive to predators. This one looked at first glance like bird droppings. When I googled \"caterpillar bird poop\", I found photos of swallowtail caterpillars that looked similar to this one. Can anyone confirm or suggest another species?