Identifying Black Swallowtail Caterpillars

• When they emerge from the egg, black swallowtail caterpillars are small, brownish and hairy. They later develop a white stripe and resemble bird droppings, which makes them easy to miss. More mature caterpillars (later "instars") develop a striking black and white stripe with a pattern of yellow blotches and can grow to as much as 2 inches in length. Like other swallowtail caterpillars they have a distinctive horn-like structure behind their heads that they will raise if they feel threatened.
  
  

Categorized as Pests

• Black swallowtails are one of the few swallowtail species that are categorized as pests. They eat large quantities of fennel and such other plants in the parsley family as dill and carrot. However, they do not usually appear in large enough numbers to become a serious problem for the domestic gardener.
  
  

Getting Rid of Black Swallowtail Caterpillars

• The easiest way to get rid of black swallowtail caterpillars is to pick them off with your hands. When threatened the caterpillars will release a harmless but foul-smelling fluid from the "horns" behind their head. Wear gloves when handling them.