superparasitism

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Infestation of an already parasitized organism by more parasites, especially of the same species.

from The Century Dictionary.

• noun The infestation of parasites by other parasites; hyperparasitism.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A form of parasitism in which the host (typically an insect larva such as a caterpillar) is attacked more than once by a single species of parasitoid.