Q: I found these creepy critters on a small citrus tree at my home. What could they be?

A: They are indeed creepy but these caterpillars turn in a giant swallowtail butterfly, Papilio cresphontes.

Their markings effectively deter predators…even humans, don’t you think?

Because the caterpillars prefer to feed on members of the citrus family, one common name is “orangedog”. They camouflage themselves to resemble bird droppings.

I hate to recommend you kill them. How about removing the caterpillars along with a few citrus leaves and let them make a chrysalis outdoors?

see
http://fireflyforest.net/firefly/2007/09/02/giant-swallowtail-butterflies-and-caterpillars/