Ask Mr. Smarty Plants

If the Citrus sinensis were native to North America, we would direct you to the webpage for that plant, where we frequently have the names and pictures of butterflies that feed on a particular plant. However, the Lady Bird Johnson Wildflower Center is dedicated to the care and protection of plants native not only to North America but to the area in which the plant is being raised. The orange originated in Southeast Asia, and has been heavily hybridized. Ordinarily, butterflies and moths prefer to feed on and use for larval hosts plants native to the same area that the butterfly is. Possibly the caterpillar you are seeing was imported with the plant; even though the orange tree was probably cultivated commercially in North America, it still may be sheltering a non-native butterfly through generations.

Since we are not entomologists and since we have no information on the orange tree in our database, let us refer you to the website of Butterfly and Moths of North America, also referred to as BAMONA.  The information on our native plant webpages originates with this organization, and they have many ways of helping you research the larval form you have found on your orange tree.

And, finally, here's another little snippet of information and pictures that we ran across that may or may not be germane to your question. It is from a website called Bug Guide, and has pictures of the Papilio cresphontes, Great Swallowtail, larva on an orange leaf.