Naked fennel; fat caterpillars. ;-)
Every summer I have as many as 12 black swallowtail caterpillars of various sizes munching on my fennel at one time and I love having them. The adult swallowtails of all varieties feed on the butterfly bushes, but the caterpillars of the black species are the only ones I see on the fennel, which I grow just for them. The "flying flowers" are sometimes as pretty in the garden as the ones on stems. I never see cocoons, though. Never have done a real search for them, but I may this year just for fun.