Look like Black Swallowtails. Are they eating dill, fennel, rue, or parsley? If so, you've got butterflies! Oh no! My advice is to go to the grocery store, buy some of those Gladware thingies, get some organic parsley to feed them, raise them indoors, and watch them become butterflies! I am biased, however.
Also, people should really identify what they have before resorting to pesticides. Thanks for inquiring about what they were before acting.
