This lovely butterfly may look innocent, but in fact its larvae are capable of completely defoliating young citrus trees.
You probably haven't seen it before because it is a recent immigrant to Florida; this butterfly's native habitat is the Middle East and Southern China. However, it likely made its way here from the Caribbean islands during a hurricane, where it has been devastating open-field citrus nurseries.
Luckily, it is not predicted to harm our citrus industry. However, residential citrus plantings have fallen prey to lime swallowtail caterpillars in Key West. They are not picky when it comes to citrus; all varieties are in danger.
The Florida Department of Agriculture and Consumer Services Division of Plant Industry (FDACS) has asked residents to notify their helpline (1-888-397-1517 or DPIHelpline@FDACS.gov) or contact their county Extension office if they suspect an infestation in their yard.
The juvenile stages of the lime swallowtail look very similar to those of our native giant swallowtail butterfly. The eggs appear nearly identical, and the young caterpillars have the same soft, bright orange to red "horns," called osmeterium, that act as a defensive organ. These horns produce a faint, unpleasant odor.
The main visual difference between our native swallowtail and the problematic invader is that the lime swallowtail caterpillar turns bright green at its final stage. The color allows it to easily blend in with citrus leaves and looks much different than the native caterpillars that remain a mottled white and brown pattern. The adult forms look nothing alike as well.
You should contact FDACS or your county Extension office if you find your citrus trees being devoured by the lime swallowtail caterpillar. The best way to protect your citrus is by frequent inspections. If you find any eggs or caterpillars, remove them by hand.