"parasites" in the noun sense
1. parasite
an animal or plant that lives in or on a host (another animal or plant it obtains nourishment from the host without benefiting or killing the host
2. leech, parasite, sponge, sponger
a follower who hangs around a host (without benefit to the host) in hope of gain or advantage
Source: WordNet® (An amazing lexical database of English)
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