Unfortunately for the orange dog caterpillar (Papilio cresphontes), its claim to fame is an uncanny resemblance to bird droppings. But before you turn up your nose, this is also the caterpillar that transforms itself into a swallowtail butterfly, with a beautiful, dramatic pattern and a 6-inch wingspan. You may find the orange dog caterpillars on citrus trees (Citrus spp.), annual fennel (Foeniculum vulgare) and prickly ash (Zanthoxylum spp.). Smaller trees could sustain lasting damage -- a few caterpillars can eat all the leaves from a small potted citrus tree. Large trees won't suffer from losing some leaves to the orange dog, though. You can get rid of orange dogs without using chemicals -- and you can leave a few to change into butterflies that will surely entertain your children.
Look for single eggs on small trees and crush them by hand. Eggs look like tiny spheres and are cream to brown or sometimes yellow. You can find them on the leaves' upper surfaces.
Pick orange dog caterpillars off of the leaves by hand or with tweezers. Crush them or put them in a jar filled with rubbing alcohol or a mixture of dish soap and water.
Sprinkle Bacillus thuringiensis powder onto the affected leaves until they are lightly coated. Apply Bt on all affected foliage in April. When the caterpillars eat it, they will die within days. This kills caterpillars that have recently hatched. Bt is a naturally occurring bacteria, effective in killing leaf-eating caterpillars. It is not dangerous to humans, and will not harm other beneficial insects.