Although parasites play important ecological roles through the direct interactions they have with their hosts, historically that fact has been underappreciated. Today, scientists have a growing appreciation of the scope of such impacts. Parasites have been reported to dominate food webs (Bakker and others, 1997; Lafferty and others, 2006), alter predator-prey relationships (Lafferty and Morris, 1996), act as ecosystem engineers (Thomas and others, 1998, 1999), and alter community structure (Poulin, 1999; Wood and others, 2007). In spite of this growing awareness in the scientific community, parasites are still often neglected in the consideration of the management and conservation of resources and ecosystems (Marcogliese, 2004). Given that at least half of the organisms on earth are probably parasitic (Price, 1980; Windsor, 1998), it should be evident that the ecological functions of parasites warrant greater attention.