Swallowtails are the largest butterflies in North America and most species have “tails” on the hindwings.  There are more than 600 species worldwide and fewer than 30 in North America.  These brightly colored butterflies are easily attracted into gardens as they nectar at a variety of flowers.  All Swallowtail caterpillars have an osmeterium, an orange, red or yellow forked organ behind the head.  This organ emits a foul-smelling odor which is a deterrent to predators.  The young caterpillars of many swallowtails resemble bird droppings.